Cronulla Fisheries Research Center

Cronulla, Australia

Cronulla Fisheries Research Center

Cronulla, Australia
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Ochwada-Doyle F.,University of New South Wales | Ochwada-Doyle F.,Sydney Institute of Marine Science | Gray C.A.,Cronulla Fisheries Research Center | Loneragan N.R.,Murdoch University | And 2 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2010

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.

Roberts D.G.,University of Wollongong | Gray C.A.,University of Wollongong | Gray C.A.,Cronulla Fisheries Research Center | West R.J.,University of Wollongong | Ayre D.J.,University of Wollongong
Molecular Ecology | Year: 2010

Populations of obligately estuarine taxa are potentially small and isolated and may lack genetic variation and display regional differentiation as a result of drift and inbreeding. Hybridization with a wide-ranging marine congener should introduce genetic variation and reduce the effects of inbreeding depression and genetic drift. However, high levels of hybridization can cause demographic and genetic swamping. In southeastern Australia hybridization occurs between obligately estuarine Black bream (Acanthopagrus butcheri) and migratory marine Yellowfin bream (Acanthopagrus australis). Here, we surveyed genetic variation at eight microsatellite loci and the mitochondrial control region of juvenile fish from five coastal lagoons (including temporal replication in two lagoons) (total n = 970) to determine the frequency and persistence of hybridization, and its likely consequence for the estuarine restricted A. butcheri. Of 688 juvenile fish genotyped 95% were either A. australis (347) or hybrids (309); only 5% (32) were A. butcheri. Most hybrids were later generation hybrids or A. butcheri backcrosses, which are likely multi-generational residents within lagoons. Far greater proportions of hybrid juveniles were found within two lagoons that are generally closed to the ocean (>90% hybrid fish within generally closed lagoons vs. 12-27% in permanently or intermittently open lagoons). In both lagoons, this was consistent across multiple cohorts of fish [79-97% hybrid fish (n = 282)]. Hybridization and introgression represent a major threat to the persistence of A. butcheri and have yet to be investigated for large numbers of estuarine taxa. © 2010 Blackwell Publishing Ltd.

Roberts D.G.,University of Wollongong | Gray C.A.,University of Wollongong | West R.J.,University of Wollongong | West R.J.,Cronulla Fisheries Research Center | Ayre D.J.,University of Wollongong
Marine Ecology Progress Series | Year: 2011

We predict estuaries to be hotspots of hybridisation between migratory marine and estuary-restricted species, although hybridisation rates may vary in space and time, reflecting the dynamic nature of estuaries and potentially widespread but erratic dispersal of marine taxa. Within estuaries, genotype frequencies may reflect past hybridisation events, with genetically intermediate and backcrossed individuals contributing to persistent hybrid swarms. In southeastern Australia, hybridisation has occurred between estuarine black bream Acanthopagrus butcheri and marine yellowfin bream A. australis, but it is unclear whether this reflects a contemporary process. We recently found that, within lakes and lagoons at the southern range limit of A. australis, hybrids were abundant and A. butcheri extremely rare, and surprisingly, we detected hybrids within a small sample of fish from the Gippsland Lakes, an estuary 250 km further south. In the present study, we compare the genotypic composition of the contemporary Gippsland Lakes population of Acanthopagrus spp. with the historical composition revealed by analysis of museum specimens. The genetic makeup of samples varied little over time, with ancestral A. butcheri virtually absent, and most introgressed individuals matching expectation for later-generation hybrids or A. butcheri backcrosses, suggesting that the lakes have supported persistent hybrid swarms. At each sampling time, the samples were genetically diverse, as measured by mean number of alleles per locus, which ranged from 8.2 to 9.2, and expected heterozygosity (He), which ranged from 0.66 to 0.70; however, we detected little allelic differentiation (FST= 0.003) across sampling times. Our data imply that introgressed populations of Acanthopagrus spp. are more widespread and persistent than previously predicted. © Inter-Research 2011.

Barnes L.M.,Macquarie University | van der Meulen D.E.,Cronulla Fisheries Research Center | Orchard B.A.,Wagga Wagga Agricultural Institute | Gray C.A.,Cronulla Fisheries Research Center
Journal of Sea Research | Year: 2013

A major challenge commonly faced in reproductive studies of teleosts is to cost effectively and safely separate oocytes from one another and from surrounding ovarian tissue. This challenge is exacerbated when ovarian tissue has been chemically preserved. Using Platycephalus caeruleopunctatus, a platycephalid species found within oceanic waters along the east coast of Australia, as an example species, within this study we describe and assess the utility of an ultrasonic cleaning device to separate oocytes from preserved ovarian tissue. The ultrasonic cleaning device was observed to separate oocytes from the surrounding ovarian tissue within less than 80. min of treatment and had no deleterious effects on the number of oocytes present. Treatment within the ultrasonic cleaning device reduced oocyte diameters at a constant rate of 3.9 μm per hour among the samples tested. As the ultrasonic cleaning device was able to separate oocytes from connective tissue within 80. min, this observed rate of reduction in oocyte diameters is unlikely to be detected at the resolution at which oocytes are traditionally measured and is less than that reported to occur using alternate chemically derived methods to separate oocytes from preserved connective tissue. Following the assessment of using an ultrasonic cleaning device to separate oocytes from ovarian tissue for P. caeruleopunctatus, this technique has been successfully employed to separate oocytes from preserved ovarian tissue for a variety of other teleost species including Macquaria colonorum, Platycephalus longispinis and Ratabulus diversidens. The use of an ultrasonic cleaning device to separate oocytes from preserved ovarian tissue will increase the efficiency of future investigations into teleost reproductive biology and potentially in other fields of research where particle separation and analysis are required. © 2012.

Gray C.A.,Cronulla Fisheries Research Center | Gray C.A.,University of New South Wales | Rotherham D.,Cronulla Fisheries Research Center | Johnson D.D.,Cronulla Fisheries Research Center
Estuarine, Coastal and Shelf Science | Year: 2011

The consistency of habitat-related differences in coastal lagoon fish assemblages was assessed across different spatial and temporal scales. Multimesh gillnets were used to sample assemblages of fish on a monthly basis for 1-year in three habitats (shallow seagrass, shallow bare and deep substrata) at two locations (>1 km apart), in each of two coastal lagoons (approximately 500 km apart), in southeastern Australia. A total of 48 species was sampled with 34 species occurring in both lagoons and in all three habitats; species caught in only one lagoon or habitat occurred in low numbers. Ten species dominated assemblages and accounted for more than 83% of all individuals sampled. In both lagoons, assemblages in the deep habitat consistently differed to those in the shallow strata (regardless of habitat). Several species were caught more frequently or in larger numbers in the deep habitat. Assemblages in the two shallow habitats did not differ consistently and were dominated by the same species and sizes of fish, possibly due to habitat heterogeneity and the scale and method of sampling. Within each lagoon, very few between location differences in assemblages within each habitat were observed. Consistent differences in assemblages were detected between lagoons for the shallow bare and deep habitats, indicating there were some intrinsic differences in ichthyofauna between lagoons. Assemblages in spring differed to those in summer, which differed to those in winter for the shallow bare habitat in both lagoons, and the deep habitat in only one lagoon. Fish-habitat relationships are complex and differences in the fish fauna between habitats were often temporally inconsistent. This study highlights the need for greater testing of habitat relationships in space and time to assess the generality of observations and to identify the processes responsible for structuring assemblages. © 2011.

Barnes L.M.,Macquarie University | Barnes L.M.,Cronulla Fisheries Research Center | Leclerc M.,Macquarie University | Gray C.A.,Cronulla Fisheries Research Center | Williamson J.E.,Macquarie University
Environmental Biology of Fishes | Year: 2011

The dietary composition and partitioning of food resources between five sympatric species of Platycephalidae inhabiting the coastal waters of New South Wales, Australia was investigated. Samples were collected monthly between March and November 2007 onboard commercial ocean prawn trawlers based in the ports of Yamba and Newcastle. Monthly percentage weight contribution of 12 prey categories was analysed to determine if diet was influenced by the variables: species, location, depth, size and maturity. Of the 959 stomachs from the five species examined, 28-54% contained prey. All Platycephalid species primarily consumed teleosts, however the diversity of prey and the proportion each prey type contributed to the overall diet varied substantially between species. Platycephalus caeruleopunctatus, P. longispinis, P. richardsoni and Ambiserrula jugosa were generalist carnivores and consumed prey from a wide variety of phyla including teleosts, crustaceans, polychaetes, molluscs and echinoderms. In contrast, Ratabulus diversidens were primarily piscivorous. Partitioning of prey resources between species was more evident in waters at Yamba than at Newcastle. Differences in diet between locations were considered a result of differential prey exploitation rather than shifts in the suite of prey consumed. Dietary composition was observed to be influenced by size, maturity status and depth however these differences were not observed for all species. © 2010 Springer Science+Business Media B.V.

Barnes L.M.,Cronulla Fisheries Research Center | Barnes L.M.,Macquarie University | Gray C.A.,Cronulla Fisheries Research Center | Williamson J.E.,Macquarie University
Marine and Freshwater Research | Year: 2011

Divergent age and growth characteristics can reduce deleterious competitive interactions between taxonomically related species facilitating coexistence. Five platycephalid fish species, Platycephalus caeruleopunctatus, Platycephalus longispinis, Platycephalus richardsoni, Ambiserrula jugosa and Ratabulus diversidens, inhabit inner continental shelf habitats along the east coast of Australia. We tested the hypothesis that the age and growth characteristics of these five species are unique. The age of each species was estimated by counting the number of opaque zones in sectioned otoliths. The maximum observed age ranged from 4 years for A. jugosa to 16 years for P. longispinis. von Bertalanffy growth functions were fitted to length-at-age data for each combination of species, sex and location and compared using likelihood ratio tests. The age and growth characteristics of each species were unique and each species displayed sexually dimorphic growth, with females growing larger than males. The unique species-specific growth characteristics may assist length-based partitioning of resources, reducing competitive interactions and facilitate coexistence between these platycephalid species. © CSIRO 2011.

Barnes L.,Cronulla Fisheries Research Center | Bellwood D.R.,James Cook University | Sheaves M.,James Cook University | Tanner J.K.,James Cook University
Marine Biology | Year: 2012

Within the tropics, mangroves and coral reefs represent highly productive biomes. Although these habitats are often within close proximity, the role and importance of mangrove habitats for reef fish species remains unclear. Throughout the Indo-Pacific, reef fish species appear to have few links with estuarine mangrove habitats. In contrast, clear-water non-estuarine mangrove habitats throughout the Caribbean support many reef fish species and may be fundamental for sustaining reef fish populations. But how important are clear-water non-estuarine mangroves for reef fishes within the Indo-Pacific? Using visual surveys during diurnal high tide, the fish assemblages inhabiting clear-water mangrove and adjacent reef habitats of Orpheus Island, Great Barrier Reef, were recorded. Of the 188 species of fishes that were recorded, only 38 were observed to inhabit both habitats. Of these, only eight were observed more than five times within each habitat. These observations provide little indication that the clear-water mangroves are an important habitat for reef fish species. In addition, although based on just a 3-month survey period, we found little evidence to suggest that these areas are important nurseries for reef fish species. The clear-water mangroves of Orpheus Island may, however, provide an additional foraging area for the few reef fish species that were observed to utilize these habitats during high tide. The difference in the importance of clear-water mangroves for reef fishes within this study compared with clear-water mangrove counterparts within the Caribbean is surprising. Although only preliminary, our observations would support suggestions that the patterns reflect the different hydrological characteristics and evolutionary histories of these two biogeographic regions. © 2011 Springer-Verlag.

Ives M.C.,Cronulla Fisheries Research Center | Scandol J.P.,University of Sydney | Greenville J.,University of Sydney
Ecological Modelling | Year: 2013

A bio-economic analysis was conducted for two fisheries using a multi-species size-based meta-population model built using the BIOMAS modelling system. The model was built to represent the prawn fisheries of northern New South Wales, Australia and calibrated against 26 years of catch and effort data from this region. A number of alternative management strategies, including the use of more size selective gear and a cap on total effort, were evaluated for their impact on the sustainability of the fish stocks and the profitability of the fleets as well as their robustness to future biological, climatic and economic uncertainties. Although the differences in management strategies were blurred by the uncertainty incorporated into the model there were still some very interesting high-level insights to be gained from the analysis. The modelled prawn species appear to be much more robust to changes in management strategies and product prices than the fleet profits, suggesting the stocks are less vulnerability to such uncertainties than the fleets that harvest them. We also found larger differences in profitability from changes in product prices than from changes in management strategies, indicating that strategies to protect product prices may be of more importance to the profitability of the fisheries than changes to fishing gear or effort levels. Such results highlight the complexity of multi-species, multi-fleet fisheries and the importance of including all relevant species and fisheries in any management strategy evaluations. This complexity can however sometimes mask simple economic truths, such as the need for strategies to maintain the market price of locally caught seafood products under the increasing pressures of international competition. © 2013 Elsevier B.V.

Gray C.A.,Cronulla Fisheries Research Center | Ives M.C.,Cronulla Fisheries Research Center | Macbeth W.G.,Cronulla Fisheries Research Center | Kendall B.W.,Cronulla Fisheries Research Center
Journal of Fish Biology | Year: 2010

Commercial gillnet and beach-seine catches of Girella tricuspidata from seven estuaries in eastern Australia were examined for differences in fork length (LF), sex and age composition, and populations were assessed for growth and mortality. Fish 220-350 mm LF dominated landings across all estuaries sampled, regardless of gear type. Few fish >10 years of age were observed in the catches, with fish aged 3-5 years, and 4-7 years, being most abundant in the catches in the four most northern estuaries and three southern estuaries, respectively. There was considerable variation in the LF of G. tricuspidata at any given age and the oldest male and female were 21 and 24 years, respectively. There were no consistent differences between sexes or latitudinal regions in the growth and mean LF at age of fish in each individual age class between 3 and 8 years. Growth of females was greater than males in the northern region, but not elsewhere. Estimates of the instantaneous rate of total mortality (Z) were dependent on estuary and year, ranging from 0·30 to 1·01, whereas the corresponding estimates of fishing mortality (F) ranged from 0·12 to 0·90. Populations of G. tricuspidata appear to have been heavily exploited, primarily relying on young fish recruiting to the fishery. The ecosystem-wide effects of harvesting this dominant mobile teleost herbivore need to be assessed further. © 2010 The Authors. Journal compilation © 2010 The Fisheries Society of the British Isles.

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