Professor Matthew Taylor

© 2020 CSIRO. Delineating stocks and quantifying population structure are critical for the management of exploited populations, but the stock structure of many species remains unclear. In New South Wales (NSW), Australia, a marine stock enhancement program for dusky flathead (Platycephalus fuscus) is developing, and knowledge of stock structure is required to inform enhancement strategies, as well as to support broader fisheries management. A combination of mitochondrial and microsatellite markers was used in this study to evaluate structuring among fish from eight estuaries, spanning the majority of the NSW coast. Pairwise comparisons of mitochondrial haplotypes revealed that seven of the eight estuaries were genetically homogeneous (St Georges Basin was distinct). Moreover, analysis of molecular variance showed that 97% of sequence diversity occurred within estuaries. The results from microsatellite markers were almost identical to those for mitochondrial DNA, with St George's Basin having the only distinct genotype, and within estuary variation accounting for 99% of the genotype variation. Isolation by distance analysis showed that <5% of genetic variation was due to distance. These results indicate that dusky flathead forms a single stock across NSW, where mixing most likely occurs during early life phases and through limited adult migration. The outlying estuary, St Georges Basin, likely suffers from limited connectivity due to a constricted entrance, and it is possible that stocking may improve local genetic diversity.

© 2019 Restoring juvenile habitat remains a key fisheries management action, but a persistent challenge is identifying the areas likely to most efficiently improve fishery outcomes. A spatial simulation model is presented that estimates the anticipated improvement in harvest of the Eastern King Prawn fishery in New South Wales, Australia, following potential restoration. By integrating environmental, biological and fisheries information gleaned from previous studies, this model suggests zones with ample larval settlement but greatly diminished habitat for juvenile life stages (recruitment), and that are in close proximity to the main fishery grounds, are likely to provide the greatest anticipated improvements in harvest. Uncertainty analyses demonstrated the particular sensitivity of these outcomes to assumptions of larval dispersal, and zone-specific recruitment at unfished conditions. The work emphasizes the utility of spatial models for restoration planning, but also the dependence of these models on information provided from empirical studies. This work also highlights the implications of input-controlled fisheries in which total effort is regulated, as this will determine the form of, and to whom, benefits of potential restoration actions will accrue.

© 2018 Spatial patterns in perfluoroalkyl substances were quantified for exploited fish and crustaceans across two contrasting Australian estuaries (Port Stephens and Hunter River). Perfluorooctane sulfonate (PFOS) was detected in 77% of composites from Port Stephens and 100% of composites from Hunter River. Most species from Port Stephens showed a clear trend with distance to source. In contrast, only a subset of species showed this trend in the Hunter River, potentially due to species movement patterns and differing hydrology. Spatial modelling showed that PFOS concentrations were expected to exceed the relevant trigger value up to ~13,500 m from the main point source for Port Stephens and ~9000 m for the Hunter River. These results represent the first major investigation of bioaccumulation of PFASs in exploited species in Australian estuaries, and highlight various factors that can contribute to spatial patterns in bioaccumulation.

© 2016 Perfluoroalkyl substances (PFASs) are being increasingly detected in a range of aquatic and terrestrial ecosystems, often resulting from the use of legacy fire-fighting foams. This study conducted an initial investigation of the concentrations of PFASs in the commercially and recreationally exploited species Dusky Flathead, Mud Crab, School Prawn, Sea Mullet, Yellowfin Bream, Eastern King Prawn and Sand Whiting, across two contaminated estuaries. All samples contained perfluoro-n-octane sulfonate (PFOS) except four Yellowfin Bream samples (two from each estuary). Perfluoro-n-octanoic acid (PFOA) was detected only in School Prawn samples from Fullerton Cove, while perfluoro-n-hexane sulfonate (PFHxS) was detected in prawn muscle and in fish liver samples from both estuaries. This study presents one of the first surveys of PFAS in a range of edible saltwater fish and crustaceans in Australia, and these baseline levels of contamination will prove useful for informing future surveys of these emerging contaminants.

© 2015 The Authors. 1. Temperature strongly regulates the distribution and fitness of ectotherms, and many studies have measured the temperature dependence of physiological performance in controlled laboratory settings. In contrast, little is known about how temperature influences ectotherm performance in the wild, so the ecological significance of physiological performance as measured in the laboratory is unclear. 2. Our aim was to measure the temperature dependence of performance in the wild for several species of fishes and to explore how temperatures that maximize performance in the wild (ToptE) are related to species biogeographies. 3. We gathered body activity and growth data from the wild for nine tropical and temperate fish species, and by fitting thermal performance curves to these data, compared ToptE to species- specific warm range boundary temperatures (the average temperature of the warmest month at equatorward range limits). To explore the degree to which trends in the wild reflect trends in physiological performance measured in the laboratory, we also compiled published data on the temperature dependence of aerobic metabolic scope in fishes and compared these to our wild fish data. 4. We found ToptE in the wild was strongly correlated with warm range boundary temperatures, and that the difference between these two temperatures (the ¿environmental heating tolerance¿) was smaller for more-tropical species. Comparison with laboratory data revealed that ToptE approaches warm boundary temperatures in the wild at the same rate that the optimal temperature for aerobic scope (ToptAS) approaches upper critical temperatures (upper Tcrit) for aerobic scope in the laboratory, meaning that environmental heating tolerances in wild fishes closely mirror physiological heating tolerance (i.e. upper Tcrit ¿ ToptAS) in captive fishes. 5. Our comparison of field- and laboratory-derived data highlights the ecological significance of aerobic metabolic scope in fishes and suggests wild fish species tend to perform best near the highest temperatures encountered in their range while maintaining a safety margin from the deleterious effects of upper critical temperatures.

© CSIRO 2016. Population structure in marine teleosts is often investigated to aid conservation and fisheries management (e.g. to assess population structure to inform restocking programs). We assessed genetic population structure of the important estuary-associated marine fish, mulloway (Argyrosomus japonicus), within Australian waters and between Australia and South Africa. Genetic variation was investigated at 13 polymorphic microsatellite markers. FST values and Bayesian estimates in STRUCTURE suggested population differentiation of mulloway within Australia and confirm strong differentiation between South Africa and Australia. The 12 Australian sample sets fell into one of four spatially separated genetic clusters. Initially, a significant signal of isolation-by-distance (IBD) was evident among Australian populations. However, further investigation by decomposed-pairwise-regression (DPR) suggested five sample sets were influenced more by genetic-drift, rather than gene-flow and drift equilibrium, as expected in strong IBD cases. Cryptic oceanographic and topographical influences may isolate mulloway populations from south-Western Australia. The results demonstrate that DPR is suitable to assess population structure of coastal marine species where barriers to gene flow may be less obvious than in freshwater systems. Information on the relative strengths of gene flow and genetic drift facilitates a more comprehensive understanding of the evolutionary forces that lead to population structure, which in turn informs fisheries and assists conservation management. Large-bodied predatory scale-fish may be under increasing pressure on a global scale, owing to a variety of anthropogenic reasons. In southern Australia, the iconic sciaenid A. japonicus (mulloway, jewfish or kob) is no exception. Despite the species supporting important fisheries, much of its ecology is poorly understood. It is possible that a greater understanding of their genetic population structure can help ensure a sustainable future for the only southern Australian sciaenid.

© 2016 The Author(s). Background: It is generally considered that on relatively homogenous marine soft sediment habitats, such as sand, fish are unlikely to show site attachment. This poses challenges for management and the evaluation of the efficacy of marine protected areas, in which soft sediments often make up more than 70 % of habitats. The blue-spotted flathead is a commercially and recreationally targeted species found on soft sediments in coastal marine waters of south-eastern Australia. There are no published data on its movement patterns. Here, using active acoustic telemetry, we aim to (a) quantify movement and habitat use of blue-spotted flathead, (b) compare area usage to no-take sanctuary zone size and (c) obtain data to aid in the design of a large passive receiver array to be used in long-term comprehensive tracking of soft sediment fish. Results: Three of five blue-spotted flathead that were tagged exhibited strong site attachment and were detected close to their release points for the entire 60-day study period. The two other fish were not detected after 4 and 25 days and were likely to have moved out of the study area (search radius ¿ 3 km). For the three fish tracked over 60 days, the area used was compact (mean ± SE = 0.021 km2 ± 0.037) and two patterns of movement were apparent: (1) a small activity space used in its entirety each day (two fish) and (2) a larger activity space in which a separate area is utilised each day (one fish). Conclusions: Our study is the first to document the movement of blue-spotted flathead, and these preliminary results demonstrate two broad movement patterns shown by this species on soft sediments in Jervis Bay. Over the course of 60 days, a majority of fish in this study showed strong site attachment; however, a number of fish also made larger-scale movements. Finally, our study suggests that a tightly spaced, passive acoustic array would provide meaningful results for this species, although strategically placed receivers outside this array would be required to detect any longer range movements.

© 2016 Published by John Wiley & Sons Ltd. Consumption is the basis of metabolic and trophic ecology and is used to assess an animal's trophic impact. The contribution of activity to an animal's energy budget is an important parameter when estimating consumption, yet activity is usually measured in captive animals. Developments in telemetry have allowed the energetic costs of activity to be measured for wild animals; however, wild activity is seldom incorporated into estimates of consumption rates. We calculated the consumption rate of a free-ranging marine predator (yellowtail kingfish, Seriola lalandi) by integrating the energetic cost of free-ranging activity into a bioenergetics model. Accelerometry transmitters were used in conjunction with laboratory respirometry trials to estimate kingfish active metabolic rate in the wild. These field-derived consumption rate estimates were compared with those estimated by two traditional bioenergetics methods. The first method derived routine swimming speed from fish morphology as an index of activity (a "morphometric" method), and the second considered activity as a fixed proportion of standard metabolic rate (a "physiological" method). The mean consumption rate for free-ranging kingfish measured by accelerometry was 152 J·g-1·day-1, which lay between the estimates from the morphometric method (µ = 134 J·g-1·day-1) and the physiological method (µ = 181 J·g-1·day-1). Incorporating field-derived activity values resulted in the smallest variance in log-normally distributed consumption rates (s = 0.31), compared with the morphometric (s = 0.57) and physiological (s = 0.78) methods. Incorporating field-derived activity into bioenergetics models probably provided more realistic estimates of consumption rate compared with the traditional methods, which may further our understanding of trophic interactions that underpin ecosystem-based fisheries management. The general methods used to estimate active metabolic rates of free-ranging fish could be extended to examine ecological energetics and trophic interactions across aquatic and terrestrial ecosystems. The contribution of activity to an animal's energy budget is an important parameter when estimating consumption, yet activity is usually measured in captive animals. We calculated the consumption rate of a free-ranging marine predator (yellowtail kingfish, Seriola lalandi) by integrating the energetic cost of free-ranging activity into a bioenergetics model. Incorporating field-derived activity into bioenergetics models probably provided more realistic estimates of consumption rate compared with the traditional methods, which may further our understanding of trophic interactions that underpin ecosystem-based fisheries management.

© 2016 The Fisheries Society of the British Isles. Using an acoustic underwater camera (Dual Frequency IDentification SONar, DIDSON), the abundance and direction of movement of fishes¿>¿80¿mm total length (LT ) in the mouth of a small South African estuary during spring and neap tidal cycles were observed. While the sizes of fishes recorded were consistent across both tide cycles, the number of fishes passing the camera was significantly greater during the smaller neap tides. Schooling behaviour was more pronounced for fishes that were travelling into the estuary compared to fishes swimming towards the ocean.

© 2015 The Fisheries Society of the British Isles. Latitudinal variation in the reproductive characteristics of a temperate marine herbivore, rock blackfish Girella elevata, was examined from three regions of the south-eastern Australian coast. Biological sampling covered 780 km of coastline, including the majority of the species distribution. The sampling range incorporated three distinct oceanographic regions of the East Australian Current, a poleward-flowing western boundary current of the Southern Pacific Gyre and climate-change hotspot. Girella elevata are a highly fecund, group synchronous (multiple batch)-spawner. Mean fork length (LF) and age at maturity were greater for females than males within all regions, with both male and female G. elevata of the southern region maturing at a greater size and age than those from the central region. Estimates of batch fecundity (FB) were greatest in the northern and southern regions, relative to the central region where growth rates were greatest. Significant positive relationships were observed between FB and LF, and FB and total fish mass. Gonado-somatic indices indicated latitudinal synchrony in spawning seasonality between G. elevata at higher latitudes, spawning in the late austral spring and summer. A late or prolonged spawning period is evident for G. elevata from the northern region. Juvenile recruitment to intertidal rock pools within the central and southern regions was synchronous with the spawning season, however, no juveniles were found within the northern region. The implications of latitudinal variation in reproductive characteristics are discussed in the context of climate and oceanographic conditions of south-east Australia.

© Inter-Research 2015. Niche segregation models underpin our understanding of speciation, population dynamics, and the evolution of foraging strategies. Many studies have evaluated changes in niche segregation dynamics over seasonal and decadal scales, but the influence of short-term stochastic processes like weather are poorly understood. This represents a problem for predicting ecosystem-level responses to the changes in weather patterns that are anticipated to occur over the coming decades. By simultaneously monitoring spatial and temporal segregation in a large estuarine piscivore and smaller benthic carnivore (mulloway Argyrosomus japonicus and sand whiting Sillago ciliata, respectively) before and after rainfall, we tested for disturbance-driven changes in species segregation. During non-rain conditions, both species were diurnally active but spatially segregated in the vertical plane (i.e. water depth). After rainfall, mulloway encroached on the whiting's vertical habitat and reversed their activity rhythm, while whiting did the opposite, strengthening their diel activity rhythm. Long-term fishery catch data were broadly consistent with this pattern, with rain-associated increases in mulloway catchability contrasting a decrease in catchability of whiting. Our example suggests short-term stochastic disturbances can drive drastic changes in fish dynamics, and highlights the significance of future changes to rainfall regimes in structuring ecosystem processes.

© 2015, Springer Science+Business Media Dordrecht. Space use and movement patterns are largely influenced by an animal¿s size, habitat connectivity, reproductive mode, and foraging behaviours; and are important in defining the broader population biology and ecology of an organism. Acoustic telemetry was used to investigate the home range, habitat use and relative movement patterns of an estuarine dependant sparid (Acanthopagrus australis, Günther). Ten fish were internally tagged with acoustic transmitters and manually tracked in a riverine estuary for four, 3-day periods. Positional data was converted into a relative index of fish movement (Minimum Activity Index, MAI), and also used to estimate kernel density distributions which approximated areas of core and total space use for each fish. Space use for A. australis was not related to fish size; although movement of each fish (MAI) increased with fish length and a reduction in water conductivity. The distance between tagged fish and mangrove habitat was correlated with time-of-day and tide level with yellowfin bream moving closer to mangroves during the daytime and on high tides. Fish movements, residency and site fidelity revealed the nature of decision-making for fish, and the conservation value of small patches of estuarine habitats.

© 2015 Elsevier Ltd. The trophic relationships of 21 species from an oceanic zooplankton community were studied using stable isotopes of carbon and nitrogen. Zooplankton and suspended particulate organic matter (POM) were sampled in three different water types in the western Tasman Sea: inner shelf (IS), a cold core eddy (CCE) and a warm core eddy (WCE). d¹⁵N values ranged from 3.9¿ for the parasitic copepod Sapphirina augusta to 10.2¿ for the euphausiid, Euphausia spinifera. d¹³C varied from -22.6 to -19.4¿ as a result of the copepod Euchirella curticauda and E. spinifera. The isotopic composition of POM varied significantly among water types; as did the trophic enrichment of zooplankton over POM, with the lowest enrichment in the recently upwelled IS water type (0.5¿) compared to the warm core eddy (1.6¿) and cold core eddy (2.7¿). The WCE was an oligotrophic environment and was associated with an increased trophic level for omnivorous zooplankton (copepods and euphausiids) to a similar level as carnivorous zooplankton (chaetognaths). Therefore carnivory in zooplankton can increase in response to lower abundance and reduced diversity in their phytoplankton and protozoan prey. Trophic niche width comparisons across three zooplankton species: the salp Thalia democratica, the copepod Eucalanus elongatus and the euphausiid Thysanoessa gregaria, indicated that both niche partitioning and competition can occur within the zooplankton community. We have shown that trophic relationships among the zooplankton are dynamic and respond to different water types. The changes to the zooplankton isotopic niche, however, were still highly variable as result of oceanographic variation within water types.

© 2015 John Wiley & Sons Ltd. Defining the oceanic habitats of migratory marine species is important for both single species and ecosystem-based fisheries management, particularly when the distribution of these habitats vary temporally. This can be achieved using species distribution models that include physical environmental predictors. In the present study, species distribution models that describe the seasonal habitats of two pelagic fish (dolphinfish, Coryphaena hippurus and yellowtail kingfish, Seriola lalandi), are developed using 19 yr of presence-only data from a recreational angler-based catch-and-release fishing programme. A Poisson point process model within a generalized additive modelling framework was used to determine the species distributions off the east coast of Australia as a function of several oceanographic covariates. This modelling framework uses presence-only data to determine the intensity of fish (fish km^-2), rather than a probability of fish presence. Sea surface temperature (SST), sea level anomaly, SST frontal index and eddy kinetic energy were significant environmental predictors for both dolphinfish and kingfish distributions. Models for both species indicate a greater fish intensity off the east Australian coast during summer and autumn in response to the regional oceanography, namely shelf incursions by the East Australian Current. This study provides a framework for using presence-only recreational fisheries data to create species distribution models that can contribute to the future dynamic spatial management of pelagic fisheries.

© CSIRO 2015. Artificial reefs are a popular fisheries management tool, but the effect of these reefs on the abundance of fish in the surrounding pelagic environment is uncertain. Pelagic baited remote underwater video (PBRUV) was used to observe the fish assemblage surrounding an offshore artificial reef (OAR), near Sydney, Australia. PBRUVs were deployed at three distances (30, 100, 500m) from the OAR, and compared with a drop camera deployed directly over the OAR. There was a significantly greater abundance of fish on the OAR, but no significant difference in abundance at the 30-, 100- or 500-m distances. Two highly mobile non-resident species (Seriola lalandi, Pseudocaranx dentex) were significantly more abundant on the OAR, but this association was not detected 30m away. The lack of a significant difference in total fish abundance, or in assemblage composition, between the 30-, 100- and 500-m distances suggests that any association with the OAR is on a localised scale (<30m). One exception was the ocean leatherjacket (Nelusetta ayraudi), which had an association detected 100m from the OAR. This predominantly small-scale effect may be influenced by the proximity of this OAR to numerous natural reefs.

© CSIRO 2015. Characterising the movement and habitat affinities of fish is a fundamental component in understanding the functioning of marine ecosystems. A comprehensive array of acoustic receivers was deployed at two near-shore coastal sites in south-eastern Australia, to examine the movements, activity-space size and residency of a temperate rocky-reef, herbivorous species Girella elevata. Twenty-four G. elevata individuals were internally tagged with pressure-sensing acoustic transmitters across these two arrays and monitored for up to 550 days. An existing network of coastal receivers was used to examine large-scale movement patterns. Individuals exhibited varying residency, but all had small activity-space sizes within the arrays. The species utilised shallow rocky-reef habitat, displaying unimodal or bimodal patterns in depth use. A positive correlation was observed between wind speed and the detection depth of fish, with fish being likely to move to deeper water to escape periods of adverse conditions. Detection frequency data, corrected using sentinel tags, generally illustrated diurnal behaviour. Patterns of habitat usage, residency and spatial utilisation highlighted the susceptibility of G. elevata to recreational fishing pressure. The results from the present study will further contribute to the spatial information required in the zoning of effective marine protected areas, and our understanding of temperate reef fish ecology.

The remote measurement of data from free-ranging animals has been termed 'biologging' and in recent years this relatively small set of tools has been instrumental in addressing remarkably diverse questions-from 'how will tuna respond to climate change?' to 'why are whales big?'. While a single biologging dataset can have the potential to test hypotheses spanning physiology, ecology, evolution and theoretical physics, explicit illustrations of this flexibility are scarce and this has arguably hindered the full realization of the power of biologging tools. Here we present a small set of examples from studies that have collected data on two parameters widespread in biologging research (depth and acceleration), but that have interpreted their data in the context of extremely diverse phenomena: from tests of biomechanical and diving-optimality models to identifications of feeding events, Lévy flight foraging strategies and expanding oxygen minimum zones. We use these examples to highlight the remarkable flexibility of biologging tools, and identify several mechanisms that may enhance the scope and dissemination of future biologging research programs. © 2014. Published by The Company of Biologists Ltd.

© 2014. Published by The Company of Biologists Ltd. Theoretical and laboratory studies generally show that ectotherm performance increases with temperature to an optimum, and subsequently declines. Several physiological mechanisms probably shape thermal performance curves, but responses of free-ranging animals to temperature variation will represent a compromise between these mechanisms and ecological constraints. Thermal performance data from wild animals balancing physiology and ecology are rare, and this represents a hindrance for predicting population impacts of future temperature change. We used internally implanted accelerometers near the middle of a species' geographical distribution and gill-net catch data near the species' latitudinal extremes to quantify temperature-related activity levels of a wild predatory fish (Platycephalus fuscus). We examined our data in the context of established models of thermal performance, and the relationship between thermal performance thresholds and biogeography. Acceleration data approximated a thermal performance curve, with activity peaking at 23° C but declining rapidly at higher temperatures. Gill-net catch data displayed a similar trend, with a temperature-associated increase and decrease in catch rates in temperate and tropical regions, respectively. Extrapolated estimates of zero activity (CTmin and CTmax) from the accelerometers were similar to the minimum and maximum mean monthly water temperatures experienced at the southern and northern (respectively) limits of the species distribution, consistent with performance-limited biogeography in this species. These data highlight the fundamental influence of temperature on ectotherm performance, and how thermal performance limits may shape biogeography. Biologging approaches are rarely used to examine thermal performance curves in freeranging animals, but these may be central to understanding the tradeoffs between physiology and ecology that constrain species' biogeographies and determine the susceptibility of ectotherms to future increases in temperature.

© 2014, Springer-Verlag Berlin Heidelberg. The influence of anthropogenic disturbance on the behaviour of wild animals is increasingly recognised for terrestrial systems. Data on free-ranging aquatic animals are comparatively scarce, and this represents a problem for estimating the consequences of human disturbance for organism fitness and therefore the functioning of aquatic systems. We used acoustic accelerometer and depth transmitters implanted in wild fish and archival stomach content data to test for relationships between the intensity of boating and the activity levels and foraging efficiency of an estuarine predatory fish, the mulloway Argyrosomus japonicus. Increasing boating activity (inferred from week-long trends in underwater noise and local maritime records) was associated with a reduction in activity levels and increased depth distributions of mulloway. Stomach content data from a nearby estuary revealed a far-lower feeding rate and altered diet composition on weekends (when boating activity is greatest) compared to weekdays for this species, and an inferred foraging success rate almost one-third that of weekdays. These data suggest the behaviour and foraging intensity of mulloway is significantly influenced by anthropogenic disturbance. The overall fitness costs of the reduction in foraging success will depend on how readily mulloway can reallocate foraging to less disturbed conditions, and the extent of stress-related responses to disturbance in this species. This study supports earlier predictions that anthropogenic disturbances like noise could have significant impacts on the behaviour and fitness of aquatic animals.

Acoustic technology is a common means to study the movements and habitat utilization of aquatic organisms. This study simultaneously assesses the relative importance of a number of major environmental variables affecting the detection range and detection frequency of acoustic tracking technology in near-shore marine environments. Transmitter power output and diel index in order of relative importance were the most influential variables affecting detection range within a temperate reef habitat. Wave height, transmitter power output, and diel index in order of relative importance were the most influential variables affecting detection range within the wash zone. Similar models resulted when examining detection frequency at 100 m within the two habitat types. Attention is also drawn to the selection of transmitter power output based upon the habitat type and environmental conditions of the study site. This study demonstrates the importance of in situ range test studies in array design and interpretation of acoustic telemetry data.

We used bulk stable isotope analysis (SIA) to examine diel feeding activity in two vertically migrating krill species, Thysanoessa gregaria and Euphausia similis, off eastern Australia. SIA indicated feeding by both species above the thermocline at night, potentially on both particulate organic matter and microzooplankton. Our results support the use of SIA to investigate vertical migration and feeding in zooplankton. © 2014 The Author. Published by Oxford University Press. All rights reserved.

© 2014 Stichting International Foundation for Animal Genetics. Stock enhancement, restocking and sea ranching are being increasingly applied in both fisheries and conservation. The contribution of hatchery stock to fishery harvest and the maintenance of the genetic structure of stocked populations are both important considerations when releasing captive-bred organisms into natural systems. Use of wild-caught broodstock generally overcomes some of the genetic problems associated with domesticated hatchery populations, but there is still a need to ensure that a sufficient proportion of the natural population contribute to production of the stocked cohort to realise the genetic benefits of using wild-caught broodstock. Releases of Penaeus (Melicertus) plebejus are under investigation as a means of increasing prawn production in recruitment-limited areas. We used the highly variable mitochondrial control region (mtCR) to assign post-larvae to maternal lineages in the hatchery and also to investigate the reproductive performance of female broodstock in terms of contribution to the production of the cohorts of post-larvae in the hatchery. Our data showed that mtCR can be a useful tool for tracking lineages and provided genetic evidence that unequal contribution and underproducing females can occur even in wild-caught broodstock. This work therefore highlights the importance of monitoring the genetic composition of pre-release hatchery stocks.

Length-based selection curves define the relative catchability of fish to specific types of fishing gear, with catchability often highest at intermediate fish lengths. Distributions such as the normal, lognormal, or gamma are often used to define "peaked" selection curves, but these have limited capabilities to describe strongly asymmetric selection relationships, such as those sometimes observed for hooks or gillnets. Another, more flexible, peaked selection curve is proposed, which is derived by combining multiple logistic distributions. While the logistic distribution is frequently used to describe monotonic selection curves, incorporating multiple logistic equations (that describe either the increasing or decreasing catchability) can define a large range of asymmetric peaked selection curves. This "peak-logistic" curve also allows nonzero asymptotic selection for the largest size classes, which may be the selection occurring in some hook-and-line fisheries. We demonstrate examples of selection in hook, haul net, and mixed hook fisheries, for which the peak-logistic curve is more appropriate than comparative lognormal and binormal selection curves. We also promote an alternative to the peak-logistic: the two-sided normal curve.

Targeted stocking involves the release of fish directly into high-quality habitat, however this is often time-consuming, expensive and difficult. Acoustically tagged hatchery-reared juvenile mulloway Argyrosomus japonicus were released in groups directly into deep-hole habitat preferred by wild conspecifics (targeted stocking), or in a non-targeted fashion near easily accessible sites that lacked high-quality habitats in the direct vicinity. Fish were tracked continuously, 24 h d-1, for 5 d following release. Fish released in a targeted fashion showed lower mean activity rates (50% less movement) and occupied higher quality habitats than fish released in a non-targeted fashion. Fish released in a non-targeted fashion also used a greater number of smaller habitat patches. The implications for improvements in behaviour and habitat usage patterns for fish released in a targeted fashion, such as improved growth and survival, are discussed. Identifying and releasing fish directly into the species' high-quality habitat may ultimately improve the success of stocking programs. © 2014 International Council for the Exploration of the Sea. All rights reserved.

© International Council for the Exploration of the Sea 2014. All rights reserved. The relationship between larval fish assemblages and coastal oceanography is the basis for much of our understanding of connectivity and productivity of fish populations. Larval fish assemblages were sampled from the upper mixed layer (<50 mdepth) at three prominent circulation features [separation of the East Australian Current (EAC), anticyclonic eddy, and cyclonic eddy] off the southeast Australian coast across three bathymetric zones (shelf, slope and ocean) for each feature. The separation of the EAC from the coast at ~ 32°S was characterized by warmer, less saline water compared with the cyclonic and anticyclonic eddies further to the south (~ 34 and ~ 35°S, respectively), which were both characterized by cooler Tasman Sea water and greater fluorescence. The anticyclonic eddy had separated from the EAC three months prior to sampling, which facilitated the movement of a cyclonic eddy from the Tasman Sea westwards to the shelf at ~ 34°S. The larval assemblage in the EAC had high numbers of fish of the families Labridae and Stomiidae. The cyclonic eddy was characterized by larval clupeids, carangids, scombrids and bothids, indicating recent entrainment of shelf waters and proximity to major spawning regions. In contrast, the anticyclonic eddy had fewer larval fish, with little evidence for entrainment of shelf assemblages into the near-surfacewaters. Myctophid swere found in high abundance across all oceanographic features and bathymetric zones. The evidence of selective entrainment of coastal larval fish into the near-surface waters of a cyclonic eddy compared with a similar anticyclonic eddy indicates a potential offshore nursery ground.

Determining the links among estuarine hydrography, habitat and spawning of estuarine-dependent fish is essential for understanding reproductive dynamics, recruitment processes and directing conservation efforts. Acoustic tracking was used to evaluate fine-scale spatial and temporal patterns in spawning activity of Percalates colonorum (estuary perch) within the Shoalhaven River, south-eastern Australia. Plankton tows were used to determine the timing of spawning events. Tagged P. colonorum exhibited movements restricted to areas of structurally complex large wooden debris and a concrete ferry landing. Egg counts confirmed that spawning events coincided with adult aggregations, whereas egg abundances peaked at night during the first 2h of the run-out tide. We postulate that spawning and recruitment success of P. colonorum is attributable to its selective spawning habitats that are (1) structurally complex to provide refuge and protection from predation, as well as congregate prey items, (2) adjacent to deep water of high velocities to maximise egg dispersal and (3) in close proximity to river entrance to facilitate coastal dispersal of eggs and inter-estuarine connectivity of larvae.

Spatial and temporal variation in the growth of a widely distributed temperate marine herbivore, Girella elevata, was examined using length-at-age data and multi-decadal otolith increment growth chronologies. In total 927 G. elevata were collected from three regions of the Australian south-east coast, extending 780. km and covering the majority of the East Australian Current, a poleward-flowing western boundary current of the Southern Pacific Gyre and climate change hotspot. A validated ageing method using sectioned sagittal otoliths was developed to enumerate both daily (juvenile fish) and annual otolith increments. G. elevata exhibited great longevity with a maximum recorded age of 45. +. yrs. Spatial variation in growth from length-at-age data was observed with the highest growth rates within the centre of the species distribution. Analysis of otolith growth chronologies of 33. yrs showed a positive relationship with the Southern Oscillation Index. Identifying links between life-history characteristics and variation in oceanographic conditions across latitudinal gradients may shed light on potential impacts of expected climate shifts on fish productivity. © 2014 Elsevier B.V.

Physicochemical variability in estuarine systems plays an important role in estuarine processes and in the lifecycles of estuarine organisms. In particular, seasonality of freshwater inflow to estuaries may be important in various aspects of fish lifecycles. This study aimed to further understand these relationships by studying the movements of a top-level estuarine predator in response to physicochemical variability in a large, temperate south-east Australian estuary (Shoalhaven River). Mulloway (Argyrosomus japonicus , 47-89 cm total length) were surgically implanted with acoustic transmitters, and their movements and migrations monitored over two years via fixed-position VR2W acoustic receivers configured in a linear array along the length of the estuary. The study period included a high degree of abiotic variability, with multiple pulses (exponentially high flows over a short period of time) in fresh water to the estuary, as well as broader seasonal variation in flow, temperature and conductivity. The relative deviation of fish from their modal location in the estuary was affected primarily by changes in conductivity, and smaller fish (n = 4) tended to deviate much further downstream from their modal position in the estuary than larger fish (n = 8). High-flow events which coincided with warmer temperatures tended to drive mature fish down the estuary and potentially provided a spawning signal to stimulate aggregation of adults near the estuary mouth; however, this relationship requires further investigation. These findings indicate that pulse and press effects of freshwater inflow and associated physicochemical variability play a role in the movements of mulloway, and that seasonality of large freshwater flows may be important in spawning. The possible implications of river regulation and the extraction of freshwater for consumptive uses on estuarine fishes are discussed. © 2014 Taylor et al.

In resource-limited populations, an increase in average body size can occur only with a decline in abundance. This is known as self-thinning, and the decline in abundance in food-limited populations is considered proportional to the scaling of metabolism with body mass. This popular hypothesis may be inaccurate, because selfthinning populations can also experience density-dependent competition, which could alter their energy use beyond the predictions of metabolic scaling. This study tested whether density-dependent competition has an energetic role in self-thinning, by manipulating the abundance of the fish Macquaria novemaculeata and tank size to partition the effects of competition from metabolic scaling. We found that self-thinning can be density dependent and that changes in intraspecific competition may be more influential than metabolic scaling on self-thinning relationships. The energetic mechanism we propose is that density-dependent competition causes variation in the allocation of energy to growth, which alters the energetic efficiency of self-thinning cohorts. The implication is that food-limited cohorts and populations with competitive strategies that encourage fast-growing individuals will have less body mass at equilibrium and higher mortality rates. This finding sheds light on the processes structuring populations and can be used to explain inconsistencies in the mass-abundance scaling of assemblages and communities (the energetic-equivalence rule). © 2013 by The University of Chicago. 0003-0147/2013/18103-53402$15.00. All rights reserved.

Estuaries are hydrographically dynamic environments, and such variability can affect the distribution and abundance of estuarine fish. Baited remote underwater video (BRUV) can be used to quantify estuarine species, but BRUV-derived data may be confounded by variable bait plume area and the associated effect on relative sampling effort. This study investigated the potential effects of current velocity on estuarine fish abundance data, and whether associated changes in bait plume size are important for benthic BRUV surveys in estuaries. BRUV sampling was conducted across two zones in two adjacent estuaries, and current velocity measured with a drogue during each BRUV deployment. Current velocity ranged from 0.02 to 0.65ms-1, resulting in potential bait plume areas that varied by orders of magnitude. The maximum number of each species (MaxN) was processed to produce a standardised (by bait plume area) and unstandardised multivariate species data set. The two data sets, whilst developed from identical video footage, yielded contrasting results. Unstandardised data was more variable, but produced a stronger correlation between abiotic variables and community structure. In addition, repeated sampling at some sites revealed significant temporal variance in community structure when data was standardised by bait plume area. Variability in sampling effort resulting from variable current velocity and associated bait plume area may confound interpretation of BRUV data. © 2013.

Activity rhythms are ubiquitous in nature, and generally synchronized with the day-night cycle. Several taxa have been shown to switch between nocturnal and diurnal activity in response to environmental variability, and these relatively uncommon switches provide a basis for greater understanding of the mechanisms and adaptive significance of circadian (approx. 24 h) rhythms. Plasticity of activity rhythms has been identified in association with a variety of factors, from changes in predation pressure to an altered nutritional or social status. Here, we report a switch in activity rhythm that is associated with rainfall. Outside periods of rain, the estuarine-associated teleost Acanthopagrus australis was most active and in shallower depths during the day, but this activity and depth pattern was reversed in the days following rain, with diurnality restored as estuarine conductivity and turbidity levels returned to pre-rain levels. Although representing the first example of a rain-induced reversal of activity rhythm in an aquatic animal of which we are aware, our results are consistent with established models on the trade-offs between predation risk and foraging efficiency. © 2012 The Author(s) Published by the Royal Society. All rights reserved.

Understanding post-release dynamics of stocked fish is essential to successful stock enhancement. This study aimed to match existing life history knowledge to optimise productivity of releases of mulloway, Argyrosomus japonicus (Temminck & Schlegel) into an urban estuary. Passive acoustic telemetry was used to monitor the movement of juvenile mulloway in the Georges River, New South Wales, Australia, and assess the effect of release site and abiotic factors on broad-scale movements of individuals for 26¿weeks. This study found that release site primarily determines the location within the estuary where individuals reside. Water temperature, atmospheric pressure and rainfall did not correlate with fish distribution, although a flood drove fish stocked from upper and mid-river sites down the estuary in February 2008. Fish gradually returned to these sites over the following 9¿weeks. Emigration rates showed an initial downstream migration and an overall egression of ~50% of fish from the release site over 26¿weeks. Fish released in this study showed a degree of site- and group-fidelity, with fish distributing according to release site. It is recommended that future releases of mulloway are undertaken directly into nursery habitat in upper estuarine regions to minimise emigration and maximise efficiency of stocking programmes. © 2013 John Wiley & Sons Ltd.

The dynamics of fish behavior, migration, and habitat use following stock enhancement will influence the outcome of recovery programs and indicate the ecological limits of the system. This study tested the effect of release density on emigration, activity patterns, and space utilization by releasing juvenile mulloway (Sciaenidae: Argyrosomus japonicus) at low and high densities and monitoring movement intensively for 336 h post release. Mulloway released at high densities had faster emigration and greater overall emigration rates than low density releases. Also, mulloway released at high densities used sub-optimal habitats at a greater frequency. Released fish dispersed into habitat patches at densities proportional to the quality of the habitat patch, consistent with density-dependent habitat selection. Targeting releases of small numbers of fish to the carrying capacity of individual patches of habitat will contribute to the success and economic viability of release programs in open systems. Releases of high densities of individuals or repeated releases at the same site may lead to increased emigration and losses from the stocked system. The capacity of a target habitat to support released fish can be rapidly assessed using pilot releases and intensive monitoring of acoustically tagged fish, prior to the implementation of large-scale release programs. © 2013 Copyright Taylor and Francis Group, LLC.

Aquaculture-based enhancement of marine fisheries includes sea ranching, stock enhancement, and restocking. A rapidly evolving context and maturing science base have effectively put these approaches into the fisheries management toolbox. Among the contextual factors are (1) a rapid expansion of captive breeding and domestication to new marine species, (2) fisheries governance systems that address the common dilemma, and (3) global environmental change impacts on coastal fisheries that increasingly call for active approaches to maintaining or increasing fisheries yields and ecosystem services. The science base of marine restocking, stock enhancement, and sea ranching continues to advance rapidly and has now reached a point where it is becoming possible to assess the likely contribution of such approaches to fisheries management goals prior to major investments being undertaken and to design enhancement programs effectively and responsibly where good potential is judged to exist. This signifies an important transition of marine fisheries enhancement from an exploratory, research-oriented endeavor to a tool in the fisheries management tool box. © 2013 Copyright Taylor and Francis Group, LLC.

This article synthesizes information on marine and estuarine release programs in Australia and evaluates potential opportunities for stock enhancement. In Australia, the scale of restocking and stock enhancement programs in marine environments has been low compared with other countries, particularly Japan, China, and the United States. However, since the early 1990s, a number of government and industry organizations have made significant investments in research and development for the release of a variety of species to evaluate the potential of releases to increase the productivity of fisheries. The scale of these research programs has varied from releases of tens of thousands of individuals (abalone Haliotis laevigata, barramundi Lates calcarifer, and mulloway Argyrosomos japonicus), hundreds of thousands (tiger prawns Penaeus esculentus and black bream Acanthopagrus butcheri), and millions (eastern king prawn Penaeus plebejus). These programs, which have shown a strong commitment to the responsible approach to enhancement sensu (Blankenship and Leber, 1995; Lorenzen et al., 2010), have resulted in increased knowledge on the population dynamics and ecology of released species and the development of bio-economic and energetic models to better plan and evaluate releases. Currently, research is continuing in New South Wales (A. japonicus, P. plebejus), Queensland (L. calcarifer), and Western Australia (A. butcheri, H. laevigata). Furthermore, Victoria is developing a plan for releasing juveniles to enhance fisheries in estuarine and marine environments, and South Australia has developed a policy for marine and estuarine stock enhancement. Policies on stock enhancement are being considered for development in New South Wales and Western Australia. These developments in policy and the introduction of fishing license fees in some states have generated renewed interest in initiating release programs in Australia that follow the responsible approach to enhancement. © 2013 Copyright Taylor and Francis Group, LLC.

Rigorous assessment of species and ecosystem biology underpins responsible marine stock enhancement. Estimation of limits to stocking density, based on ecosystem productivity and energetic requirements of stocked species, can be used to gauge the appropriate magnitude of release densities, minimizing waste of resources, and the possibility for adverse stocking effects. A generalized mass-balance model (generalized predatory impact model) for stocking density estimation has been developed. The approach is based around the principles of ECOPATH and accounts for dynamic estimation of stocking-related ecosystem relationships at fine temporal (days) and spatial scales. The main parameter inputs include probability distributions for key biological and life-history traits of stocked species and estimates of primary productivity for the target ecosystem. The energetic requirements of stocked fish are evaluated in terms of growth and mortality as well as ontogenetic transitions in diet, habitat use, morphology, and migration. The theoretical carrying capacity for a stocked species within a given arena is assessed from primary productivity, levels of predation by stocked fish on different trophic groups, and a specified level of acceptable trophic impact. A Monte Carlo analysis of uncertainty is used to provide a probability distribution of stocking densities for a given trophic impact. The model is applied for stocking juveniles of snook (Centropomus undecimalis) in Sarasota, FL, USA, and mulloway (Argyrosomus japonicus) in Georges River, NSW, Australia. The model is useful for estimating an appropriate stocking density when planning pilot-scale fish releases. Such releases should be carefully monitored to validate model assumptions and determine density-dependent and other environmental effects. © 2013 Copyright Taylor and Francis Group, LLC.

Eastern king prawn, Penaeus (Melicertus) plebejus, is an endemic Australian species which is heavily exploited both commercially and recreationally in estuaries and in offshore trawl fisheries across several jurisdictions. P. plebejus shows extensive movement throughout the known distribution range during various life history stages (Montgomery et al. in Fish Res 80:80-87, 2007). It is currently unknown whether there is a full migration throughout the species range, or step-wise migration, and identifying the origins of important spawning populations remains as a challenge. We report 20 high resolution microsatellite markers, to address such questions and assist conservation planning for long-term sustainability. © 2013 Springer Science+Business Media Dordrecht.

Stable isotope analysis is often used to identify the relative contributions of various food resources to a consumer's diet. Some Bayesian isotopic mixing models now incorporate uncertainty in the isotopic signatures of consumers, sources and trophic enrichment factors (e.g. SIAR, MixSIR). This had made model outputs more comprehensive, but at the expense of simple model evaluation, and there is no quantitative method for determining whether a proposed mixing model is likely to explain the isotopic signatures of all consumers, before the model is run. Earlier linear mixing models (e.g. IsoSource) are easier to evaluate, such that if a consumer's isotopic signature is outside the mixing polygon bounding the proposed dietary sources, then mass balance cannot be established and there is no logical solution. This can be used to identify consumers for exclusion or to reject a model outright. This point-in-polygon assumption is not inherent in the Bayesian mixing models, because the source data are distributions not average values, and these models will quantify source contributions even when the solution is very unlikely. We use a Monte Carlo simulation of mixing polygons to apply the point-in-polygon assumption to these models. Convex hulls ('mixing polygons') are iterated using the distributions of the proposed dietary sources and trophic enrichment factors, and the proportion of polygons that have a solution (i.e. that satisfy point-in-polygon) is calculated. This proportion can be interpreted as the frequentist probability that the proposed mixing model can calculate source contributions to explain a consumer's isotopic signature. The mixing polygon simulation is visualised with a mixing region, which is calculated by testing a grid of values for point-in-polygon. The simulation method enables users to quantitatively explore assumptions of stable isotope analysis in mixing models incorporating uncertainty, for both two- and three-isotope systems. It provides a quantitative basis for model rejection, for consumer exclusion (those outside the 95% mixing region) and for the correction of trophic enrichment factors. The simulation is demonstrated using a two-isotope study (15N, 13C) of an Australian freshwater food web. © 2013 British Ecological Society.

Understanding movement patterns, habitat use and behaviour of fish is critical to determining how targeted species may respond to protection provided by "no-take" sanctuary zones within marine parks. We assessed the fine and broad scale movement patterns of an exploited herbivore, luderick (Girella tricuspidata), using acoustic telemetry to evaluate how this species may respond to protection within Jervis Bay (New South Wales, Australia). We surgically implanted fourteen fish with acoustic transmitters and actively and passively tracked individuals to determine fine and broad scale movement patterns respectively. Eight fish were actively tracked for 24 h d-1 for 6 d (May 2011), and then intermittently over the following 30 d. Six fish were passively tracked from December 2011 to March 2012, using a fixed array of receivers deployed across rocky reefs around the perimeter of the bay. Luderick exhibited strong site fidelity on shallow subtidal reefs, tending to remain on or return consistently to the reef where they were caught and released. All eight fish actively tracked used core areas solely on their release reef, with the exception of one fish that used multiple core areas, and four of the six fish passively tracked spent between 75 to 96% of days on release reefs over the entire tracking period. Luderick did move frequently to adjacent reefs, and occasionally to more distant reefs, however consistently returned to their release reef. Luderick also exhibited predictable patterns in movement between spatially distinct daytime and night-time core use areas. Night-time core use areas were generally located in sheltered areas behind the edge of reefs. Overall, our data indicate luderick exhibit strong site fidelity on shallow subtidal reefs in Jervis Bay and suggests that this important herbivore may be likely to show a positive response to protection within the marine park. © 2013 Ferguson et al.

Animal activity patterns evolve as an optimal balance between energy use, energy acquisition, and predation risk, so understanding how animals partition activity relative to extrinsic environmental fluctuations is central to understanding their ecology, biology and physiology. Here we use accelerometry to examine the degree to which activity patterns of an estuarine teleost predator are driven by a series of rhythmic and arrhythmic environmental fluctuations. We implanted free-ranging bream Acanthopagrus australis with acoustic transmitters that measured bi-axial acceleration and pressure (depth), and simultaneously monitored a series of environmental variables (photosynthetically active radiation, tidal height, temperature, turbidity, and lunar phase) for a period of approximately four months. Linear modeling showed an interaction between fish activity, light level and tidal height; with activity rates also negatively correlated with fish depth. These patterns highlight the relatively-complex trade-offs that are required to persist in highly variable environments. This study demonstrates how novel acoustic sensor tags can reveal interactive links between environmental cycles and animal behavior. © 2013 Taylor et al.

Fish stocking is an increasingly common management tool for freshwater and marine environments and is often used to create and maintain fisheries in closed waters. The densities at which fish are stocked can have a large impact on a stocking programme's success and sustainability. Stocking densities in impoundment sport-fisheries, for example, are often based on social or practical factors, and ecologically based stocking models are needed to assist the selection of stocking densities that are appropriate for the environment. In this study, stocking density is calculated with a numerical model that balances the supply of prey production with the energetic demand of stocked fish. The model aims to deliver outcomes over a range of potential management objectives, by providing specific consumption scenarios that represent the trade-off between population abundance and individual body size in stocked fisheries. The model uses a steady-state population approach to calculate stocking density, which optimises population consumption by maintaining a consistent biomass distribution and encourages sustainable stocking by considering the energetic needs of all cohorts. Carrying capacity is represented by the steady-state stocking density under a minimum consumption scenario (when fish meet only their minimum energetic needs). The comparison between a desired consumption rate and the existing level of production is used to assess the status or 'health' of the existing population and is used to determine whether stocking can occur and whether stocking densities can be sustainably increased. The probability of incorrectly assuming populations are achieving a given consumption level is also estimated, which is an ideal approach for interpreting multiple probability distributions. A Monte-Carlo analysis of uncertainty was used to provide a probability distribution of stocking density of Australian bass (Macquaria novemaculeata) in three Australian impoundments under various seasonal and consumption scenarios. The likely consumption rates of the existing populations were determined using historical stocking densities, which showed that the three populations were of reasonable health, although one impoundment may be overstocked. The steady-state stocking densities depended on the desired consumption rate, and there was an eightfold difference in the stocking density aimed at providing large 'trophy' fish and the density required to reach carrying capacity. Model outputs of existing abundance and biomass density agreed with empirical estimates of abundance and relative density in these impoundments, which provides support to the model's accuracy. This supply-demand approach to estimating the range of appropriate stocking densities shows promise as a decision-support tool for stocked impoundments and other closed fisheries. © 2012 Blackwell Publishing Ltd.

Several studies have described strong relationships between body size and the accumulation of trace metals in animal tissues. However, few of these studies have utilized aging techniques to control for age related effects. We utilized relative body size (gy-1) of a model flounder species, Pseudorhombus jenynsii, in order to control for age related effects on growth and size measurements. We investigated links between relative body size, concentrations of trace metals in flounder muscle tissue, physico-chemical variables (temperature, salinity, pH, and turbidity), and levels of trace metals in the sediment. Flounder were sampled using an otter trawl net in the inner areas of eight estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. Our results indicate that this commonly eaten fish is accumulating significant levels of some trace metals in their muscle tissue, both in relatively unmodified and heavily modified estuaries. Concentrations of Cu, Zn and Fe in muscle tissue, as well as temperature, showed a negative relationship to the relative body size of flounder. In contrast, Se and Hg in muscle showed a positive relationship to relative body size. Observed growth patterns indicate that these effects are not driven by age related differences in metabolic activity. Instead, our results suggest that differences in food supply or toxicological effects may be responsible for the observed relationships between relative body size and concentrations of Cu, Zn, and Se in muscle tissues. The use of otolith aging and growth measurement techniques represents a novel method for assessing the relationships between trace metal accumulation and the relative body size of fish in a field environment. © 2012 Elsevier B.V.

The mechanisms that drive density dependence are rarely studied in the applied context of population management. We examined the potential for competition for food and shelter and the resulting demographic density dependence to influence how well populations of the eastern king prawn Penaeus plebejus Hess can recover following marine stock enhancement programmes in which captive-bred juveniles are released into the wild. Specifically, manipulative laboratory experiments were used to quantify the differential effects of competition for food and competition for shelter on survival of wild and captive-bred P. plebejus as densities were increased and as each category of P. plebejus (wild or captive-bred) was supplemented with the alternate category. Increasing population densities when food and shelter were limited lowered survival for both categories. When food was limited, survival of both categories was unaffected by addition of the alternative category. Adding wild P. plebejus to their captive-bred counterparts when shelter was limited under laboratory conditions resulted in significantly higher mortality in captive-bred individuals. In contrast, adding captive-bred P. plebejus to wild individuals under these conditions did not affect wild P. plebejus. We conclude that if the current results can be extended to wild conditions, competition for shelter may lead to the loss of captive-bred P. plebejus, thereby reducing the intended outcomes of stock enhancement. This highlights the importance of investigating interactions between wild and captive-bred animals prior to stock enhancement to predict long-term outcomes and identify situations where stock enhancement could be an effective response to the loss of populations or recruitment limitation. © Inter-Research 2012.

Dietary analysis revealed that an impoundment population of Australian bass Macquaria novemaculeata holds a generalist niche, but one arising from persistent individual specialization and interindividual variation. This 'individual specialist' strategy appeared adaptive, but the strength of individual specialization was largely independent of variation in diet composition, except during blooms of Daphnia sp. Diet composition and dietary overlap showed only moderate ontogenetic variation, and niche breadth showed no relationship with ontogeny. Macquaria novemaculeata showed an asymmetric predator and prey size distribution, consistent with many aquatic predators, with positive relationships between fish size and average, maximum and minimum prey size. There was no asymmetry in the relative size-based niche breadths of individuals, however, which indicates that the niche is a fixed 'window' of relative prey sizes. The difference in the dietary niche and prey-size relationships of M. novemaculeata at the population and individual levels highlights the necessity of assessing the niche at both these levels. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Fine-scale movement patterns in penaeid prawns are rarely observed in situ, but are essential in understanding habitat use, foraging, and anti-predator behaviour. Acoustic telemetry was applied to examine the activity, space utilization, and habitat use of the eastern king prawn Penaeus (Melicertus) plebejus, at small temporal and spatial scales. Tracking of sub-adult P. plebejus (n = 9) in Wallagoot Lake (36.789°S, 149.959°E; 23 April-12 May 2009) and calculation of a minimum activity index (MAI) revealed high variation in activity rates across diel periods and in different habitats. Elevated activity rates and movement indicated foraging in unvegetated habitats during the night. Areas within the 95 and 50% space utilization contours averaged 2,654.1 ± 502.0 and 379.9 ± 103.9 m2, respectively, and there was a significant negative relationship between these areas and prawn activity rates in unvegetated habitats. This study provides the first estimates of prawn activity rates and space utilization in the field. Application of acoustic telemetry can increase knowledge of prawn movements and their interactions with other marine species in different habitats. © 2011 Springer-Verlag.

Swarms of the salp Thalia democratica periodically occur off southeast Australia following the austral spring bloom of phytoplankton. The present study aimed to determine the abundance and size/stage distribution of T. democratica and their relationship with copepods in 3 water types of the western Tasman Sea. Samples were taken from vertical net hauls along 4 cross-shelf transects spaced along 200 km of the New South Wales coast, from the East Australian Current (EAC) sepa - ration zone, around 32.5° S, to off Sydney (34° S). Temperature-salinity signatures grouped stations into 3 distinct water types: inner shelf water, EAC and upwelled water. Although common across all stations, T. democratica was significantly more abundant in inner shelf waters compared to both EAC and upwelled water. Analysis of population structure (aggregate buds, aggregate females, aggregate males, immature solitaries and mature solitaries) also identified higher proportions of reproductive aggregates and their offspring in inner shelf water. This salp population structure was significantly different in the EAC regions, characterised by a paucity of the solitary stages, higher temperatures and lower chlorophyll a concentrations. A weak negative correlation was identified between T. democratica and copepod abundance. In the present study, the maximum abundance of T. democratica was twice the highest globally recorded abundance and 10-fold greater than maximum abundances sampled from the continental shelf and slope waters off southeast Australia during the period from 1938 to 1942. © Inter-Research 2011.

Changes to larval fish assemblages may have far reaching ecological impacts. Correlations between habitat modification, contamination and marine larval fish communities have rarely been assessed in situ. We investigated links between the large-scale distribution of stressors and larval fish assemblages in estuarine environments. Larval fish communities were sampled using a benthic sled within the inner and outer zones of three heavily modified and three relatively unmodified estuaries. Larval abundances were significantly greater in modified estuaries, and there were trends towards greater diversity in these systems. Differences in larval community composition were strongly related to sediment metal levels and reduced seagrass cover. The differences observed were driven by two abundant species, Paedogobius kimurai and Ambassis jacksoniensis, which occurred in large numbers almost exclusively in highly contaminated and pristine locations respectively. These findings suggest that contamination and habitat alteration manifest in substantial differences in the composition of estuarine larval fish assemblages. © 2011 Elsevier Ltd. All rights reserved.

The larvae of two carangid fishes, silver trevally (Pseudocaranx dentex) and yellowtail scad (Trachurus novaezelandiae), were compared among coastal water masses and the East Australian Current (EAC). Samples followed a north to south gradient including a southern region of upwelling, generated as the EAC separated from the coast. Mean larval carangid densities were greater in the mixed layer (10-30m) than the surface, but there was no difference between inshore and offshore stations or along latitudinal gradients. Overall, P. dentex recent larval growth over two days pre-capture was faster than T. novaezelandiae, and faster at inshore, coastal stations than in the EAC. Integrated larval growth rate (mmd-1) was usually faster at inshore stations for both species. T. novaezelandiae were enriched in both nitrogen (d15N) and carbon (d13C) stable isotopes relative to P. dentex. Larvae of both species captured within the upwelling region were enriched in d15N and depleted in d13C relative to other sites. Recent larval growth had a significant positive relationship with fluorescence (as a proxy of chlorophyll a biomass), and integrated larval growth rate had a significant positive relationship with fluorescence and larval isotope (d15N) composition. Recent and integrated growth of larval T. novaezelandiae and P. dentex was enhanced by EAC separation and upwelling, and also in coastal water; stimulated by food availability, and potentially through exploitation of a different trophic niche. © 2010 Elsevier Ltd.

In recent decades there has been a significant effort to establish marine sanctuaries for the purpose of protecting marine biodiversity and ecological processes. While many studies have demonstrated that marine sanctuaries increase the abundance, diversity, and trophic level of marine fish communities, few have compared these parameters across multiple levels of protection and human modification. This study utilized baited remote underwater video to compare fish assemblages between marine parks, between different levels of protection within parks (sanctuary and habitat protection zones), and between parks and highly modified systems with similar ecological communities. It was demonstrated that sanctuary zones have higher abundance of targeted fish species compared with other areas within some marine parks. The total abundance of targeted species and abundances of some key fisheries species (e.g. pink snapper) were found to be higher in sanctuary zones. This suggests that increased protection may be effective at improving these aspects of the fish assemblage. However, when marine parks were compared with highly modified environments it was found that targeted species were much more abundant in the highly modified systems. Community composition of entire fish assemblages also differed between these levels of modification and economically important fisheries species contributed most to this difference. These findings suggest that while highly protected sanctuary zones may increase the abundance of targeted fish compared with less protected areas within the same estuary, highly industrialized or urbanized systems, not typically chosen as marine parks, may actually support more targeted species of fish. It was demonstrated that forms of modification in addition to fishing pressure are having large effects on fish assemblages and productivity. © 2011 John Wiley & Sons, Ltd.

Fish are commonly stocked into impoundments globally, yet their patterns of habitat use in this variable environment are rarely incorporated into the management of stocking density. The movement and distribution of Australian bass Macquaria novemaculata (Perchichthyidae) were monitored in two impoundments to assess whether: (1) impoundment populations exhibit behaviour typical of wild or riverine percichthyids; (2) changing gradients of temperature and dissolved oxygen influenced distribution; and (3) the volume of available habitat should be incorporated into the management of these fisheries. Habitat use was determined with a combination of gill netting and ultrasonic telemetry using depth-coded tags. Tagged fish displayed both crepuscular and migratory behaviour typical of the Percichthyidae, but also showed a previously unobserved division between littoral and pelagic foraging strategies. Australian bass showed no obvious thermal preferences, but avoided areas with dissolved oxygen 4mgL-1. In one impoundment, a combination of hypoxia and water extraction reduced the volume of available habitat to 15% of maximum in March 2009, which coincided with increased catch per unit effort (CPUE) and decreased fish condition. The adaptive behaviour of Australian bass makes them well suited to the variability of impoundments, but annual and stochastic events of habitat reduction should be considered when planning stocking regimes for these fisheries. © CSIRO 2011.

The potential for hatchery-release programs to augment the harvest rates of fisheries can be limited by environmental factors associated with survival, growth and body condition among released individuals. We assessed spatial and temporal variability in the condition of postlarval and small juvenile (1-10 mm carapace length) eastern king prawns Penaeus plebejus Hess sampled from an estuarine population subjected to pilot releases of 3 million postlarvae per year in southeastern Australia. Variability in the length-weight relationship was used as a measure of condition and compared between (1) autumn/winter and spring/summer periods and (2) bare and macrophytic habitats for P. plebejus sampled from a population in a closed estuarine system. At a reference carapace length of 3.97 mm, condition was ~14% higher for individuals sampled from bare habitat and ~16% higher for those sampled during autumn/winter compared, respectively, with individuals sampled within macrophytic habitat and during spring/summer. Further experimental work on the factors investigated here is encouraged to increase our understanding of the environmental characteristics and mechanisms that lead to improved condition and thus persistence of stocked populations of P. plebejus. © Inter-Research 2011.

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination. © 2011 McKinley et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Marine stock enhancement is often characterized by poor survival of hatchery-reared individuals due to deficiencies in their fitness, such as a diminished capacity to avoid predators. Field experiments were used to examine predation on Penaeus plebejus, a current candidate for stock enhancement in Australia. We compared overall survival of, and rates of predation on, wild P. plebejus juveniles, naïve hatchery-reared juveniles (which represented the state of individuals intended for stock enhancement) and experienced hatchery-reared juveniles (which had been exposed to natural predatory stimuli). Predation was examined in the presence of an ambush predator (Centropogon australis White, 1790) and an active-pursuit predator (Metapenaeus macleayi Haswell) within both complex (artificial macrophyte) and simple (bare sand and mud) habitats. Overall survival was lower and rates of predation were higher in simple habitats compared to complex habitats in the presence of C. australis. However, the three categories of juveniles survived at similar proportions and suffered similar rates of predation within each individual habitat. No differences in survival and rates of predation were detected among habitats or the categories of juveniles when M. macleayi was used as a predator. These results indicate that wild and hatchery-reared P. plebejus juveniles are equally capable of avoiding predators. Furthermore, exposure of hatchery-reared juveniles to wild conditions does not increase their ability to avoid predators, suggesting an innate rather than learned anti-predator response. The lower predation by C. australis in complex habitats was attributed to a reduction in this ambush predator's foraging efficiency due to the presence of structure. Ecological experiments comparing wild and hatchery-reared individuals should precede all stock enhancement programs because they may identify deficits in hatchery-reared animals that could be mitigated to optimize survival. Such studies can also identify weaknesses in wild animals, relative to hatchery-reared individuals, that may lead to the loss of resident populations. © 2010 Elsevier B.V. All rights reserved.

Larval Euphausia similis were collected off temperate eastern Australia in spring 2004 and 2006 to evaluate the relationships between larval populations, mesoscale oceanographic variability, and the wider planktonic community. Larval E. similis were present in greater numbers in the East Australian Current (EAC) relative to productive coastal waters. Larval E. similis density was homogenous across the EAC-Tasman Sea frontal region, but larvae were smaller in the Tasman Sea. Larval E. similis density was not enhanced within a cold core eddy relative to the surrounding EAC. We observed a negative correlation between larval E. similis density and larval fish density, and a weak positive correlation with fluorescence. Evaluation of a significant fish density×fluorescence interaction term showed that the effect of fish density was reduced at high fluorescence values. Analysis of normalized biomass size spectrum (NBSS) provided evidence for potential competitive exclusion of copepods by krill. Data presented in this study suggest a predatory influence on surface E. similis populations by mesopelagic larval fish. The degree of predation appears to be dependent on food availability, potentially mediated by changes in the physiological condition of krill. © 2010 Elsevier Ltd.

The vertical dry strength of rice hull containers was the highest of all containers tested. Plastic containers and paper containers had similar vertical dry strengths. Containers composed of 80% cedar fiber and 20% peat (Fertil), composted dairy manure (Cowpot), and peat had lower dry vertical dry strengths than the aforementioned containers but had higher vertical dry strengths than those composed of bioplastic (OP47), coconut fiber, and rice straw. Rice hull containers and paper containers had the highest lateral dry strengths. Rice straw, Cowpot, and plastic containers had similar dry lateral strengths, which were significantly higher than those of OP47, Fertil, coconut fiber, and peat containers. Highest dry punch strengths occurred with traditional plastic and Cowpot containers, while the lowest dry punch strengths occurred with OP47, Fertil, coconut fiber, peat, and rice straw containers. Plastic, rice hull, and paper containers had the highest wet vertical and lateral strengths. Plastic containers had the highest wet punch strength, while Fertil, Cowpot, and peat containers had the lowest wet punch strengths. When saturated substrate was placed into containers and the substrate surface and drainage holes were sealed with wax, plastic, OP47, and rice hull containers had the lowest rates of water loss per unit of container surface area, while peat, Fertil, and rice straw containers had the highest rates of water loss per unit of container surface area. The amounts of water required to produce a geranium (Pelargonium × hortorum) crop were significantly higher and the average irrigation intervals were shorter for peat, Fertil, coconut fiber, Cowpot, and rice straw containers than for traditional plastic containers. The amounts of water required to produce a geranium crop and the average irrigation intervals were similar among plastic, rice hull, and OP47 containers. Algal and fungal coverage on the outside container walls averaged 47% and 26% for peat and Fertil containers, respectively, and was higher than for all other containers tested, which had 4% or less algal and fungal coverage. After 8 weeks in the field, Cowpot containers had decomposed 62% and 48% in the Pennsylvania and Louisiana locations, respectively. Peat, rice straw, and Fertil containers decomposed 32%, 28%, and 24%, respectively, in Pennsylvania, and 10%, 9%, and 2%, respectively, in Louisiana. Coconut fiber containers had the lowest level of decomposition at 4% and 1.5% in Pennsylvania and Louisiana, respectively.

Carbon and nitrogen stable isotope ratios were analysed for hatchery-reared, recaptured and wild mulloway, Argyrosomus japonicus, to investigate temporal and growth-related changes in isotopic composition for stocked fish after release, and to evaluate changes in isotopic composition in terms of ontogenetic dietary switches. d13C and d15N values decreased and increased, respectively, after release. The isotope composition of released fish was distinct from wild fish until 200 days after release, but after 200 days post-release fish did not differ significantly from wild fish of similar or greater sizes. Abrupt dietary transitions from crustaceans to teleost fish (>50 cm total length (TL)) were evident in a rapid d13C and d15N change in wild mulloway, and d15N was significantly greater in wild fish >65 cm TL compared with wild fish <50 cm TL. Multivariate carbon and nitrogen isotopic data were suitable for separating stocked and wild fish for up to 200 days after release, but did not separate wild fish grouped according to dietary composition. Carbon and nitrogen isotopic composition closely reflected dietary transitions and rapid adaptation by stocked mulloway to wild diets, which was evident in a high tissue turnover rate of up to 0.017 day -1. Stable isotopes are a useful tool for examining the integration of released fish into stocked ecosystems and can be used to describe convergence in the diets of wild and released fish. © 2010 CSIRO.

Behaviour of juvenile mulloway Argyrosomus japonicus were investigated under laboratory conditions to determine the efficacy of estimating predation mortality using tethering. The occurrence and duration of stressed behaviour was evaluated for individual A. japonicus that were hooked but untethered, hooked and tethered and unhooked and untethered (free swimming), both in schools and in isolation. Tethered and hooked treatments showed a significantly higher incidence and duration of stressed behaviour over controls, but stressed behaviour was lower for hooked but untethered fish in the presence of a school. Artifacts associated with elevated stress may reduce the reliability of estimates of relative predation derived from tethering data for schooling fishes.

Global attempts to offset declines in fishery populations through stock enhancement have had varied levels of success due to the absence of preliminary studies to determine which habitats best support release species and the mechanisms controlling their distribution. Habitat preference was examined as a possible mechanism driving distribution of postlarval Penaeus plebejus, a current candidate prawn for stock enhancement in Australia. Occupancy of complex (artificial macrophyte) and simple (bare sand and mud) habitats by postlarvae was compared in the presence and absence of a choice between the habitats. Predation mortality was also compared amongst these habitats. P. plebejus settled into the different habitats randomly during the night, but actively selected macrophyte over the simple habitats during the day. Mortality caused by the predatory fishes Centropogan australis and Acanthopagrus australis was higher in simple habitats than in complex habitats, but was similar across habitats when large penaeid prawns, Metapenaeus macleayi (which are tactile rather than visual feeders), were used as predators. Postlarvae may select macrophyte habitats during the day to lower predation risk, but because nighttime foraging efficiency is reduced in their predators, which are primarily visual hunters, this may preclude the need of postlarvae to obtain shelter in macrophyte habitats at night. Predation mortality of stocked P. plebejus may be minimized by releasing postlarvae directly into macrophyte habitats. Studies such as these must precede all stock enhancement attempts because they identify optimal release strategies and allow ecological and financial costs of enhancement to be weighed against projected benefits, and thereby assess the practicality of enhancement as a management option. © Inter-Research 2009.

Hatchery-reared Argyrosomus japonicus (Temminck & Schlegel) were released into estuaries of varying habitat between 1996 and 2004, and growth and recruitment to the fishery evaluated. Fish stocked earlier in summer had significantly faster growth rates (P < 0.01), and post-stocking mortality ranged from 1.1% to 11.7% within 7 day post-release. Argyrosomus japonicus stocked in the Georges River in 2003 and 2004 yielded fishery independent recapture rates up to 0.2%. For A. japonicus stocked in Smith's Lake in 1997 and 2004, growth rates, timing of recaptures and increases in commercial catches suggested recruitment to the fishery by 18 months. The 1997 stocking led to a 30-fold increase in A. japonicus catch, but stocking was not financially viable, with a cost:benefit ratio of 2.1. Small, shallow coastal lagoons may represent experimental units for refining stocking strategies, but are not optimal for A. japonicus. The potential for density-dependent effects, and complex relationships between growth, habitat and mortality, highlighted the need for a thorough understanding of species - system interactions. Pilot releases can contribute to this understanding, particularly assessment of habitat requirements, and season, site and size-of-release. © 2009 Blackwell Publishing Ltd.

Scales from hatchery-reared, stocked and wild mulloway Argyrosomus japonicus (Temminck and Schlegel) captured in the Georges River, and a library of mulloway scales from coastal New South Wales, were examined for the presence of scale checks. Checks specific for hatchery-reared fish were present in 100% of recaptured hatchery-reared mulloway; the origin of which was confirmed by the presence of a chemical mark in the otolith or fin spine. Up to 7% of wild mulloway were incorrectly classified as hatchery-reared on the basis of these checks. An abrupt reduction in salinity from 35 to 5 and 6days starvation successfully induced checks in the scales of hatchery-reared mulloway. The marking efficiency for stocking checks was comparable to that obtained using oxytetracycline hydrochloride, and supports the short-term use of scale stocking checks to evaluate mulloway stock enhancement programmes in Australia. © 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd.

Habitat, diet, and life history information were used to estimate appropriate stocking density and the potential predatory impact of a stocked finfish. Our Predatory Impact Model uses data from the literature for fish in freshwater or estuarine habitats. Model simulations were run for the Georges River Recreational Fishing Haven (RFH), Sydney, to evaluate appropriate stocking density and associated predatory impact. The estuary contained about 1,760,000 m2 of key nursery habitat for mulloway (Argyrosomus japonicus), and 10% of mysid shrimp production within this habitat was assigned to support stocked fish, as mysids represent the immediate forage requirements of stocked mulloway. Given these values, this section of river could support 17,500 stocked mulloway of 8 cm TL. During the first 3.5 years post stocking, when mulloway are predominantly estuarine residents, predatory impact includes 1 t mysid shrimp, 80 t forage fish, 45 t prawns, 3 t miscellaneous invertebrates and 5 t cephalopods. For comparison, this predatory impact represents 107%, 154%, and 24% of the commercial fishery in Botany Bay/Georges River for forage fish, prawns, and cephalopods, respectively, for 3.5 years before the declaration of the RFH. To maximize the benefit of the approach, a targeted approach to stocking should be taken. Stocked fish should be stocked directly into key habitats, as opposed to being released from a few shore-based sites within the estuarine system. Copyright © Taylor and Francis Group, LLC.

The mysids Rhopalopthalmus egregius, Haplostylus dakini and Doxomysis australiensis are abundant yet unstudied omnivorous crustaceans in Australian estuaries. Habitat use and population dynamics were investigated for these species over spring and summer in the Tweed River, Australia, to explore their ecological role in estuarine ecosystems. Overall, mysids were concentrated in shallow unvegetated and deep unvegetated estuarine habitats. H. dakini were most abundant in shallow and deep bare habitats at night, whereas R. egregius were most abundant in deep bare habitats during the night. D. australiensis were present across all habitats in the night, but negligible numbers were present during the day. Significantly greater numbers of R. egregius and D. australiensis were sampled during the new moon, compared with the full moon. Significantly larger R. egregius and D. australiensis individuals were present in benthic habitats at night, indicating possible partitioning of habitat for juvenile and adult subpopulations. Adaptive foraging strategies and habitat use facilitates the coexistence of sympatric mysid species, H. dakini and R. egregius, and within-species habitat partitioning allowed juvenile R. egregius to avoid interaction with adult R. egregius. The observed dynamics minimize inter- and intra-specific predation between mysids, and by other predators, while optimizing access to key trophic resources. © CSIRO 2008.

The preferred habitats, home range and activity patterns of sub-adult mulloway Argyrosomus japonicus (Sciaenidae) in the Georges River, New South Wales, Australia, were investigated using ultrasonic telemetry. Tags were surgically implanted in 9 hatchery-reared and 12 wild-caught mulloway (330 to 730 mm total length, TL). Fish were tracked for 2 periods of continuous tracking over 72 h in a 15 km section of river, once daily for a 20 d period, and up to 3 times mo-1 for 11 mo. Key habitats were identified as discrete holes or basins up to 20 m deep. Mulloway preferred this deep hole habitat as small fish (hatchery-reared, 300 to 500 mm TL) remained in these deep holes both day and night, while large fish (wild, 500 to 800 mm TL) ventured outside the holes at night. Maximum home range of small and large mulloway was 6000 and 17710 m2, respectively, and home range correlated significantly with length. Small fish moved up to 7 km d-1 while large fish moved up to 16 km d-1. Small fish released in shallow water initially had significantly greater movements than those released directly over deep holes, with movement up to 10 km in 3 d. Activity patterns varied between small and large fish, with significantly larger movements by large fish during the night and early morning than daytime. Five wild-caught mulloway tracked over 11 mo showed strong fidelity to holes within their particular home range. Mulloway should be stocked directly into their deep holes to minimise movements. The use of key habitats by mulloway indicate that their survival will be sensitive to stocking density. Optimal stocking density could be estimated from the area of key habitat in the target estuary. © Inter-Research 2006.

Prey importance and ontogenetic transitions in the diet of stocked and wild mulloway (Argyrosomus japonicus) were compared between a southeast Australian riverine estuary and a coastal lagoon. Stomach content analysis of fish captured from these estuaries in 1977-1979, 1997-1998, and 2003-2005 revealed size-specific and estuary-specific diets. Mysid shrimp were most common in diets of fish < 250 mm total length (TL), and prawns were common in diets of fish measuring 301-450 mm. Forage fish were most abundant in diets of mulloway > 500 mm. Index of Relative Importance (IRI) of forage fish increased with TL, while IRI of mysids decreased with TL. Prawn IRI was greatest for fish 150-600 mm TL. Comparisons between benthic resources and dietary composition revealed that Georges River mulloway consumed prey categories in proportions similar to those in their environment. No mysid shrimp were detected in the coastal lagoon or in the diet of mulloway captured there; growth was comparable to the Georges River. Hatchery-reared fish fed < 16 d after stocking, indicating normal behavioural adaptation after release. Dietary information can be used to optimize stocking locations, times, and densities, as well as estimate potential effects of mulloway on potential prey and wild conspecifics. © 2006 Estuarine Research Federation.

Juvenile mulloway Argyrosomus japonicus (54.6 ± 4.6 mm total length, mean ± S.E.) were immersed in a range of oxytetracycline (OTC) solutions ranging between 0-600 mg l-1 in salinities of 5 (diluted sea water) and 35 (undiluted sea water), and alizarin complexone (ALC) solutions ranging between 0-60 mg l-1 in undiluted sea water, for 6, 12 and 24 h. Optimal marking conditions were 600 mg l-1 OTC for 24 h in a salinity of 5, and 30 mg l-1 ALC for 12 h respectively. Mark quality (MQ) was assessed using a score of 0-3 in both otoliths and anal fin spines, with a score >2 found to be acceptable for adequate mark identification. Acceptable marks were not produced using OTC in undiluted sea water. Immersion in OTC or ALC, or reduced salinity had no effect on survival relative to controls. Transverse sections of vertebrae from the ALC and OTC treatments with the highest otolith mark quality showed no discrete marks. Optimal marking techniques were used to produce double marks with a 3 day interval between marking, and marking techniques were applied to 130 000 juvenile mulloway in batch mode with minimal mortality. A numerical model of the chemical behaviour of OTC in sea water describes the decline of available OTC in increasing salinity, so that a species' salinity tolerance and successful marking can be optimized. © 2005 The Fisheries Society of the British Isles.

The responsible approach to marine stock enhancement is a set of principles aimed at maximising the success and benefits of artificially re-stocking depleted fisheries. The benefits of such an approach are evident in the 400% increase in survival of stocked striped mullet in Hawaii through refinement of release techniques, however financially or temporally constrained stocking programs in Australia have not adhered to all principles. A pragmatic approach to address these principles is proposed, using international examples and Australian marine finfish pilot stockings of barramundi, mulloway, sand whiting, dusky flathead and black bream. Biological ranking of candidate species by estuarine residency, a low natural-mortality to growth ratio, a large L 8 and comparison by recreational value and available rearing technologies, show that mulloway, barramundi and sea mullet are ideal species for stocking in Australia. Australian intermittently closed opening landlocked lagoons and recreational fishing havens, especially near cities, provide experimental opportunities to apply this approach and stock suitable species through small-scale pilot experiments. This would allow evaluation of production and carrying capacity, and density dependent processes with respect to optimal stocking strategies unconfounded by emigration and commercial fishing practices. Twenty per cent of Australians fish each year, and harvest approximately 27 000 t of finfish. Stocking recreationally important species in Australia should give a greater financial benefit, which is spread across a larger cross-section of the community, compared to stocking to enhance commercial fisheries. The pragmatic application of the responsible approach, and stocking of fast growing estuarine residents into recreational fishing havens would enhance the benefit from marine stocking. © 2005 The Fisheries Society of the British Isles.