The impact of environmental toxicants on the fertility of female animals. This study aims to address a problem of national significance; determining the impact of commonly used environmental toxicants (pesticides) on the fertility and health of female animals, both agricultural and native. This project expects to generate new knowledge in the fields of ovarian biology, female fertility and toxicology by using a combination of mouse and marsupial animal models. The expected outcomes include the e ....The impact of environmental toxicants on the fertility of female animals. This study aims to address a problem of national significance; determining the impact of commonly used environmental toxicants (pesticides) on the fertility and health of female animals, both agricultural and native. This project expects to generate new knowledge in the fields of ovarian biology, female fertility and toxicology by using a combination of mouse and marsupial animal models. The expected outcomes include the establishment of interdisciplinary collaborations and provision of world-class training for staff and students in the field of reproductive biology. This project should provide significant benefits, such as improved chemical management in livestock production and the development of marsupial conservation action plans.Read moreRead less
Genetic Stock Structure Of Commercially Important Deep Sea Crab Species
Funder
Fisheries Research and Development Corporation
Funding Amount
$20,000.00
Summary
Two deep sea crab species crystal crab (Chaceon albus) and champagne crab (Hypothalassia acerba) are captured by both the West Coast Deep Sea Crustacean Managed Fishery (WCDSCMF) and South Coast Crustacean Managed Fishery (SCCMF). The greatest catches of these two species are landed by the WCDSCMF. As part of the MSC certification process for the WCDSCMF, information is required on the stock structure of (PI 1.2.3) and recent surveillance of this fishery identified; "…there is little informatio ....Two deep sea crab species crystal crab (Chaceon albus) and champagne crab (Hypothalassia acerba) are captured by both the West Coast Deep Sea Crustacean Managed Fishery (WCDSCMF) and South Coast Crustacean Managed Fishery (SCCMF). The greatest catches of these two species are landed by the WCDSCMF. As part of the MSC certification process for the WCDSCMF, information is required on the stock structure of (PI 1.2.3) and recent surveillance of this fishery identified; "…there is little information on the stock structure of crabs.... and this may weaken a stock assessment". Therefore information on the genetic stock structure will assist in the stock assessment of crystal crab and future MSC re-certification of the WCDSCMF. The information will also aid in the stock assessment and management of the SCCMF crab fisheries. The recent stock assessment of crystal crab in the SCCMF indicated an unacceptable level of stock depletion. Catches in this area have been highly cyclical unlike those on the west coast. This pattern is very similar to that of rock lobster and blue swimmer crab, whereby the main spawning stock resides on the west coast with large and consistent catches, while those on the south coast are sporadic with recruitment e.g. possibly only flowing down in strong Leeuwin Current years. These south coast areas are considered a resource ‘sink’. Irrespective of the similarities, the south coast deep-sea crab fisheries are still managed conservatively under the assumption of self-recruiting (they are not treated as sink populations). Determination of the recruitment linkages between the west and south coast fisheries will have marked implications on the management arrangement required for both fisheries. Objectives: 1. Determine the stock structure of the crystal crab Chaceon albus 2. Determine the stock structure of the champagne crab Hypothalassia acerba 3. Assess the implication of stock structures on the management arrangements required for both fisheries Read moreRead less
Implementation Of Dynamic Reference Points And Harvest Strategies To Account For Environmentally-driven Changes In Productivity In Australian Fisheries
Funder
Fisheries Research and Development Corporation
Funding Amount
$552,027.00
Summary
Recently, the risks resulting from not accounting for variability in productivity have become translated into potential risks associated with environmentally driven trends in recruitment, particularly the risk created by ongoing declines in recruitment (and/or growth) driven by climate-change induced trends in water temperature, weather and current patterns.
A number of southeast Australia fish stocks have failed to 'recover' following substantial reductions in catch and effort, and a n ....Recently, the risks resulting from not accounting for variability in productivity have become translated into potential risks associated with environmentally driven trends in recruitment, particularly the risk created by ongoing declines in recruitment (and/or growth) driven by climate-change induced trends in water temperature, weather and current patterns.
A number of southeast Australia fish stocks have failed to 'recover' following substantial reductions in catch and effort, and a number of research projects have concluded that some of these have undergone an environmentally-driven reduction in productivity. A productivity shift has already been demonstrated for Eastern Jackass Morwong, with the stock-recruit relationship and reference points being adjusted to reflect this change. Ecosystem and climate-change modelling have predicted increasing likelihood of similar changes in productivity for a number of Australian fish stocks.
Current harvest strategies assume either equilibrium or some average B0, and associated target (B48) and limit (B20) reference points. Use of equilibrium B0-based reference points and harvest strategies do not correctly reflect the natural dynamics of stocks where productivity changes. This can lead to sub-optimal management, either over-utilising a reduced productivity stock or under-utilising an increased productivity stock. In contrast, reference points based on some proportion of naturally variable unfished biomass (Bunfished or dynamic B0) will fluctuate to follow environmentally-driven productivity changes. Dynamic reference points have been evaluated and adopted for a number of international fisheries.
The need to adapt stock assessment methods and harvest strategies to explicitly and justifiably account for shifts in productivity has been recognised by the AFMA Resource Assessment Group for the Southern and Eastern Scalefish and Shark Fishery (SESSF), not least as a result of clearly evident declines in biomass (Jackass Morwong, Redfish) or recruitment (Silver Warehou) that cannot be attributed to fishing under current productivity assumptions.
Objectives: 1. To review relevant international research and management approaches to account for environmentally-driven productivity change in stock assessments, reference points and harvest strategies for selected Australian fish stocks. 2. To identify and describe circumstances and fish stocks for which dynamic reference points should or should not be used in stock assessments and harvest strategies, and develop appropriate methodology for conducting assessments using dynamic reference points. 3. To identify selected candidate fish stocks showing likely environmentally-driven productivity change, conduct comparative assessments for these stocks using equilibrium and dynamic reference points, and prepare a candidate harvest strategy that includes dynamic reference points for testing in the FRDC Multi-Species Harvest Strategy project. 4. To make recommendations on future implementation of dynamic reference points and harvest strategies for Australian fish stocks. 5. To develop and improve methods for detecting and quantifying changes in productivity (growth and recruitment) in stock assessments, to relate these to environmental mechanisms causing productivity changes, and to evaluate data needs, including environmental indices, required to usefully detect and evaluate productivity change under various circumstances. 6. To consider and evaluate options for effective harvest control rules, incorporating dynamic reference points, that might appropriately respond to changes in fish stock productivity, including environmentally driven trends in productivity. 7. To identify environmental circumstances and fish stock characteristics under which it would be appropriate and advisable to move to using assessments and management approaches incorporating dynamic productivity and reference points, vs. stocks for which dynamic approaches offer no benefit compared to existing equilibrium approaches. 8. To make recommendations on future stock assessment approaches, data requirements, harvest control rules and management approaches incorporating environmental indicators, dynamic productivity and dynamic reference points for Australian fish stocks. Read moreRead less
Examining The Relationship Between Fishery Recruitment, Essential Benthic Habitats And Environmental Drivers In Exmouth Gulf
Funder
Fisheries Research and Development Corporation
Funding Amount
$514,056.00
Summary
Stock status in the EGPMF is assessed by monitoring fishery-independent and fishery-dependent catch rates (used as indices of recruitment and spawning stock levels) relative to specified reference points. However, in recent years factors other than the spawning stock index appear to be responsible for low levels of prawn recruitment. Given recent indications that the distribution and abundance of seagrass habitats may influence prawn recruitment there is a need to better understand the rela .... Stock status in the EGPMF is assessed by monitoring fishery-independent and fishery-dependent catch rates (used as indices of recruitment and spawning stock levels) relative to specified reference points. However, in recent years factors other than the spawning stock index appear to be responsible for low levels of prawn recruitment. Given recent indications that the distribution and abundance of seagrass habitats may influence prawn recruitment there is a need to better understand the relationship between prawn recruitment, environmental conditions and habitats. Understanding these relationships is required to clarify the uncertainty around stock fluctuations and improve stock assessments. The information is also required so that management can be more cognisant of the impacts of environmental conditions on annual recruitment variability and implement adaptive management strategies, such as altering seasonal arrangements, to prevent overfishing.
Similarly, the recent MSC assessment of the EGPMF fishery has highlighted the need to clarify the uncertainty in fishery independent surveys and stock assessments including the influence of environmental factors on indices, and collect environmental and habitat data to detect changes in risk to habitat due to fishing including ongoing monitoring of critical habitat types.
Therefore, the development of broad scale fishery specific, cost effective monitoring techniques is essential to assess and monitor the association between critical fish habitats, environmental drivers and prawn recruitment. These techniques need to be developed at appropriate temporal and spatial scales to allow for early intervention of appropriate management measures, such as adjusting spatial and temporal closures, to ensure the long term sustainability of stocks and maintain MSC certification. Given that recruitment in a number of the State’s other invertebrate fisheries appears to be influenced by environmental drivers developing techniques to understand these relationships is a critical component of ensuring the management of WA’s fisheries resources is based on robust science.
Objectives: 1. Collate and review historical, satellite, habitat and environmental data for the Exmouth Gulf and Shark Bay ecosystems to identify factors that may influence recruitment. 2. Assess the ability of different techniques, at various spatial and temporal scales, to identify, assess and monitor critical fish habitat and environmental conditions which may affect recruitment patterns of prawns into the Exmouth Gulf Prawn Managed Fishery 3. Collect local environmental and productivity data to assess the feasibility of collecting broad scale data remotely. 4. Develop a cost effective monitoring program for critical fish habitat and environmental drivers which allows the development of mitigation measures to assist in alleviating poor recruitment events. Read moreRead less
Presentation At World Congress Of Aquaculture And Fisheries (Xiamen, China) On Biosecurity And Aquatic Animal Health
Funder
Fisheries Research and Development Corporation
Summary
I have been asked to Chair the Session and provide a presentation to the WCAF Conference during session 2-4: Biosecurity and Aquatic Animal Health, where I will talk about shared responsibility, cost sharing and collaborative responses with the Australian Aquatic Animal Health and Biosecurity Management Framework and take part in a panel session. My presentation will include an overview of the AAH and Biosecurity management system and the the development of the Aquatic Deed (and more importantly ....I have been asked to Chair the Session and provide a presentation to the WCAF Conference during session 2-4: Biosecurity and Aquatic Animal Health, where I will talk about shared responsibility, cost sharing and collaborative responses with the Australian Aquatic Animal Health and Biosecurity Management Framework and take part in a panel session. My presentation will include an overview of the AAH and Biosecurity management system and the the development of the Aquatic Deed (and more importantly the biosecurity /Aquatic animal health policy components that come directly from it as front end components of the Deed) as a one of a kind innovation that puts Australia on the map with respect to Aquatic EAD response management as well as Aquatic EAD avoidance and minimisation.
In addition to a significant Biosecurity and Aquatic Animal Health component, WCAF also features sessions on Aquatic Animal Nutrition, Disease & Health Management, there are some topics of interest including Aquaculture Reproduction & Breeding Technology (Resilience to The Environmental Variability And Sustainability), Commercialisation & Economics, Investment, Insurance of Aquaculture, Sustainable Culture and Development of Aquaculture & Fisheries, Smart Fisheries, and Culture, Seafood, and Global Change: Anthropological Perspectives on Food Habits and Aquatic Food Resources in a Time of Increasing Demographic and Climate Change Impacts. This are very relevant with respect to Aquaculture development in Australia and it would be beneficial to hear these presentations.
Objectives: 1. Presentation to WCAF (AAH and Biosecurity Session on Day 2): To elucidate and provide an update on developments in Australian Biosecurity and Aquatic Animal Health Policy Development 2. Take part in and Industry Panel on Day 1 and Chair the AAH and Biosecurity Session on Day 2: Better understand global biosecurity, aquatic animal health, nutrition, breeding and environmental performance and global aquaculture health policy development in a global context 3. Attendance at WCAF: To get a better understanding of global biosecurity, aquatic animal health, nutrition, breeding and environmental performance and global aquaculture health policy development 4. To be part of an Australian presence at a large Fisheries and Aquaculture Forum, and engage with other delegates with a view to facilitate improved cooperation/collaboration. And learn about AAH and Biosecurity Policy around the World Read moreRead less
Understanding The Relationship Between Commercial Prawn Species Population Dynamics, Fishing Patterns And Climate In The Shark Bay World Heritage Area In Western Australia
Funder
Fisheries Research and Development Corporation
Funding Amount
$575,616.00
Summary
There is growing concern the sustainability of prawns may be at increased risk due to a higher proportion of small prawns in commercial catches and fishery-independent recruitment surveys. The brown tiger prawn stock experienced its lowest recruitment in 3 years. The causes of change in prawn size and the magnitude of recruitment remain unknown, but we can identify some plausible hypotheses. These include; slowing of growth with lower winter temperatures, a reduction in productivity, changes ....There is growing concern the sustainability of prawns may be at increased risk due to a higher proportion of small prawns in commercial catches and fishery-independent recruitment surveys. The brown tiger prawn stock experienced its lowest recruitment in 3 years. The causes of change in prawn size and the magnitude of recruitment remain unknown, but we can identify some plausible hypotheses. These include; slowing of growth with lower winter temperatures, a reduction in productivity, changes to timing of spawning, total fishing pressure and intra-annual fishing patterns. It is possible that changes are influenced by interactions between some or all of these.
A higher proportion of smaller prawns in commercial catches has continued despite adjustments to management. In addition, the location of prawns during the season has become less predictable. There is an urgent and immediate need to understand the mechanisms underlying these changes to make the necessary management changes to ensure long-term sustainability. The approach will be to use existing datasets to test hypotheses about potential associations between physical (e.g. temperature, rainfall), biological (e.g. seagrass cover), and fishery (e.g. prawn recruitment) variables that we would expect to occur under plausible cause-effect scenarios. These scenarios will be developed through discussions between researchers with different skill sets and insights from prawn fishers.
The study will adopt a multi-disciplinary approach to utilise expertise of researchers with skills beyond conventional fisheries science and management, including oceanography, ecology, data science and mathematics, and research specific to the SBPMF and synthesis of the fishing industry. The objectives clearly address both WARAC and the Prawn IPA key priorities of adaptive approaches to changing climate.
The objectives are supported by DPIRD managers and some sections of the Shark Bay prawn trawl industry. An independent review of the prawn fishery conducted in April 2019 by Malcolm Haddon provided recommendations regarding research priorities. The review found the objectives addressed a number of key uncertainties identified in the review and suggested they were urgent. Objectives: 1. Understand the impact of changing temperature and other environmental parameters (e.g. seagrass, flooding events) on the reproductive cycles, growth and distribution patterns of western king and brown tiger prawns 2. Understand the relative contribution of autumn and spring spawning stock to the catch and prawn size composition to assess why there are more small prawns in the fishery at the start of the year and whether harvesting large volumes of small prawns impact subsequent recruitment. 3. Develop performance indicators for the Shark Bay Prawn Harvest Strategy (HS) (which is currently based on abundance indices), if appropriate, that are related to size of prawns. 4. Determine if information on ecological processes and primary productivity are sufficient to construct predictive models of prawn carrying capacity. Read moreRead less
Climate Driven Shifts In Benthic Habitat Composition As A Potential Demographic Bottleneck For Western Rocklobster: Understanding The Role Of Recruitment Habitats To Better Predict The Under-size Lobster Population For Fishery Sustainability
Funder
Fisheries Research and Development Corporation
Funding Amount
$433,791.00
Summary
The marine heat waves (MHW) of 2010/11, 2011/12 and 2012/13 provide a benchmark with which to investigate changes in habitat composition and potential flow on effects to the fishery.
A 2018 independent review of the science used for stock assessment of the fishery recommended that studies should be undertaken to
a) investigate the impacts of the previous MHW on juvenile recruitment to the fishery and,
b) to better understand the role of habitat composition in recruitme ....The marine heat waves (MHW) of 2010/11, 2011/12 and 2012/13 provide a benchmark with which to investigate changes in habitat composition and potential flow on effects to the fishery.
A 2018 independent review of the science used for stock assessment of the fishery recommended that studies should be undertaken to
a) investigate the impacts of the previous MHW on juvenile recruitment to the fishery and,
b) to better understand the role of habitat composition in recruitment
To understand the impact of habitat change on the fishery, either through warming events or changes in coastal processes, we need an increased understanding of the role of habitat on the survivorship and growth of puerulus, post-puerulus, juvenile and adult life stages of lobster.
In the 40 year time-series of puerulus settlement index a very strong relationship has persisted between puerulus abundance and commercial lobster catches 3 - 4 years larter (de lestang et al., 2010). An undersize catch rate index, based on historical (1985 - present) catch-rate records, evidenced the existence of a strong correlation between puerulus and undersize catch rate (de Lestang pers. com.). However, two-four years after the MHW of 2010/11, this relationship degraded, with the observed catch rate of lobsters being far less than expected at northern locations of the fishery. Although the relationship has now started to return to its historical form, the severity and longevity of its departure are cause for concern and highlight the marked impact future MHW or changes in coastal processes could have on the fishery.
Change in the extent and configurations of coastal habitats is already occurring in response to natural physical forcing (coastal processes) and accelerated by climate change related stressors. It is crucial to have a detailed knowledge of how habitat change affects survival and recruitment key life-stages of the western rock lobster, so these can be taken into consideration for management practices that ensure the sustainability of the fishery. Such information is currently lacking. Objectives: 1. The overall objective is to evaluate the implications of habitat change for the western rock lobster fishery, by determining the relative importance of habitat for the survivorship and growth of critical western rock lobster life stages, to inform the interpretation of existing settlement and recruitment metrics where and when habitat change also occurs. This will be examined via four linked objectives: 2. Synthesise evidence of habitat change: use novel and historical habitat imagery and other remote sensing datasets to determine the spatial extent of habitat loss and recovery, either attributed to 2011/2012 marine heat wave or changes in coastal processes. 3. Investigate fine-scale correlations in anomalies between predicted and observed undersize catch rate index and areas of habitat loss and recovery, either attributed to 2011/2012 marine heat waves or changes in coastal processes. 4. Evaluate evidence of essential benthic habitat for juvenile lobster, by measuring how habitat quality (cover and composition) influences lobster survival. 5. Create a spatial index of essential habitats to inform the interpretation of existing settlement and recruitment metrics. Read moreRead less
Development Of A Sustainable Scallop (Ylistrum Balloti) Fisheries Enhancement Program For Western Australia: Preliminary Feasibility Study
Funder
Fisheries Research and Development Corporation
Funding Amount
$920,050.00
Summary
A substantial rise in future demand for seafood is forecast with ocean fishery productivity projected to decline by up to 50% in some fisheries due to ecological disruptions. A key challenge therefore will be maintaining fishery productivity. Shark Bay and the Abrolhos Islands scallop fisheries are prime examples - following the extreme marine heat wave of 2011 lost income from these fisheries is estimated at $53 million GVP, or $155 million including multipliers.
The integration of aq ....A substantial rise in future demand for seafood is forecast with ocean fishery productivity projected to decline by up to 50% in some fisheries due to ecological disruptions. A key challenge therefore will be maintaining fishery productivity. Shark Bay and the Abrolhos Islands scallop fisheries are prime examples - following the extreme marine heat wave of 2011 lost income from these fisheries is estimated at $53 million GVP, or $155 million including multipliers.
The integration of aquaculture and wild fisheries is becoming increasingly recognised as a tool for enhancing fishery productivity (Taylor et al, 2017). Re-stocking and stock enhancement following recruitment failure could lead to faster fishery recoveries, and also be used to supplement natural recruitment to provide a more consistent and higher yield harvest from year to year. Development of supply chains for scallops into domestic and overseas high-value live markets requires consistent supply. Due to climatic variability and highly variable natural recruitment there is an urgent need to investigate scallop stock enhancement using hatchery-produced juveniles in WA.
A key element for success will be the development of reliable, efficient and scalable seed production systems, which will be based on previous research findings integrated novel, contemporary shellfish production technology. During this project, 16 million cultured scallop spat are planned to be released. The annual yield of scallops from the Rottnest SWF Zone A is 25 to 50 tonnes (whole scallop weight), or approximately 250,000 - 500,000 scallops assuming an average weight of 0.100 kg/whole scallop. This Project aims to release on average 8 million spat each year of the Project (600,000, 1,500,000 and 6,000,000 of 10mm, 5mm and 2mm spat respectively), which could contribute 45,000 hatchery-produced scallops to the catch each year assuming 2.50%, 1.00% and 0.25% of 10mm, 5mm and 2mm spat released respectively were captured, increasing yield by 8.3 – 16.6 % in the annual production, demonstrating the feasibility of scallop stock enhancement.
Objectives: 1. Develop and validate genetic tools to determine parentage / origin of scallops and measure genetic diversity 2. Develop hatchery and nursery protocols for consistent production of scallop spat 3. Develop strategies and methodologies for scallop spat deployment and stock enhancement sampling; measurement of seeded scallop spat survivorship; assessment of effect of spat size at deployment on survival rates; duration of growth to market size; determine impact of enhancement Read moreRead less
Assessing The Biology And Connectivity Of Deep-water Finfish On Australia’s East Coast And The Impact Of Fleet Dynamics
Funder
Fisheries Research and Development Corporation
Funding Amount
$433,228.00
Summary
Deep-water finfish are an increasingly important fisheries resource on Australia's east coast that has been subjected to recent and rapid growth in fishing pressure across commercial, recreational, and charter sectors. Drivers of increased targeting of deep-water species likely include depletion of inshore stocks leading to effort shifts to deeper areas, advances in technology facilitating more effective targeting of deep-water species and changing market dynamics leading to increased profitabil ....Deep-water finfish are an increasingly important fisheries resource on Australia's east coast that has been subjected to recent and rapid growth in fishing pressure across commercial, recreational, and charter sectors. Drivers of increased targeting of deep-water species likely include depletion of inshore stocks leading to effort shifts to deeper areas, advances in technology facilitating more effective targeting of deep-water species and changing market dynamics leading to increased profitability. However, sustainable management of deep-water finfish stocks requires species-specific information on fundamental life history characteristics and stock structure to inform evidence-based management that is currently lacking.
Deep-water species are often characterised by slow growth, late maturity, and clustered distributions around pockets of suitable habitat that leave them vulnerable to overfishing. It is necessary to determine how such traits and connectivity among populations affect the sustainability of fisheries for key deep-water species on Australia's east coast. Management of deep-water species is also complicated by cross-jurisdictional distributions including Queensland, New South Wales, and Commonwealth managed fisheries.
Currently, due to the lack of fundamental biological information, key deep-water species are managed using basic harvest strategies set to trigger enhanced management and scientific focus when such need arises, which is now occurring. For example, the 2021 commercial harvest of Bar Cod (Epinephelus ergastularius) in Queensland exceeded double the mean harvest from 2011-2015, triggering a requirement for the first stock assessment of this species. Anecdotally, recreational catches in Queensland of other key species including Flametail Snapper (Etelis coruscans) and Goldband Snapper (Pristipomoides multidens) have substantially increased in recent years, with the latter given priority status for future stock assessment. New South Wales DPI has indicated a particular need for research focus on Bass groper (Polyprion americanus) and Hapuku (Polyprion oxygeneios) due to the complete lack of biological information required for fisheries management of these species, both of which are now quota managed. Recreational fishing effort is important to quantify because this sector has come to dominate the deep-water fishery in some areas where commercial fishing effort is sparse. Changing fleet dynamics and the uptake of technological advances in fishing gear have also increased fishing power for deep-water species in ways that are poorly understood.
This project aims to address these issues with a cross-jurisdictional collaboration between Qld DAF, NSW DPI, and AFMA supported by the University of Queensland providing fundamental information on the biology and population connectivity of key deep-water species. Project staff are well placed to leverage their existing networks and will also build new relationships with stakeholders throughout the deep-water fishery to pursue sample collection from all available sources including commercial fishers, processors, and recreational and charter fishers. Archived samples and targeted fishery-independent sampling will also be employed to secure sufficient samples to provide confident estimates on life history parameters and population connectivity to inform stock assessment. Additionally, we aim to develop novel methods to improve recreational reporting of deep-water catches and improve estimates of fishing power effects on catches of deep-water finfish.
Objectives: 1. Describe the life history characteristics of key deep-water species, e.g., Bar Cod, Flametail Snapper, and Goldband Snapper 2. Understand the stock structure and connectivity of deep-water species in Queensland and New South Wales 3. Investigate and implement novel methods for improving recreational catch reporting of deep-water species 4. Improve estimates of fishing power in the deep-water line fishery by reviewing (as opposed to trialling) historic and current fishing technologies Read moreRead less
Cost-effective, Non-destructive Solutions To Developing A Pre-recruit Index For Snapper
Funder
Fisheries Research and Development Corporation
Funding Amount
$541,804.00
Summary
The population dynamics and fishable biomass of Snapper in South Australia are fundamentally driven by high inter-annual variation in recruitment, i.e. the numbers of 0+ juveniles that recruit to populations. Throughout the 2000s, SA’s Snapper stocks experienced different trends in recruitment that led to extraordinarily different trends in fishery catches. For the Spencer Gulf/West Coast Stock successive poor year classes led to the significant decline in fishable biomass, and a ‘depleted’ st ....The population dynamics and fishable biomass of Snapper in South Australia are fundamentally driven by high inter-annual variation in recruitment, i.e. the numbers of 0+ juveniles that recruit to populations. Throughout the 2000s, SA’s Snapper stocks experienced different trends in recruitment that led to extraordinarily different trends in fishery catches. For the Spencer Gulf/West Coast Stock successive poor year classes led to the significant decline in fishable biomass, and a ‘depleted’ stock status. In contrast, the Gulf St. Vincent Stock increased to unprecedented levels due to numerous strong recruitment year classes, but since 2015 has also experienced considerable declines in fishery catches. In 2019 it was classified as ‘depleting’. From 2018, concerns about both stocks prompted a comprehensive review of the fishery management approach. This resulted in significant changes to the management strategy including a spatial and long-term fishery closure. Despite this, there remains the need to monitor the stocks and demographic processes. Given the significance of variable recruitment for Snapper, the need for regional, annual estimates of recruitment as an indicator of future trends in fishable biomass has re-emerged. Between 2000 and 2010, recruitment surveys were done in Northern Spencer Gulf, for which the sampling methodology, i.e. otter trawling, was non-selective and destructive of benthic and demersal biota. One need here is to develop a cost-effective, non-destructive sampling strategy for future annual sampling. Also, there is the need to develop a better understanding of larval ecology, connectivity, and the causes of variable recruitment. Combined benefits from addressing both needs would significantly enhance predicting future trends in fishable biomass.
Objectives: 1. To develop our understanding of the processes that regulate recruitment based on finalising datasets from previous research projects that relate to the early life history, and larval and juvenile ecology of Snapper, as well as the annual variation in environmental factors 2. To undertake an empirical study to compare the utility and effectiveness of several potential sampling methodologies to provide a relative recruitment index for Snapper and to develop a sampling strategy for future surveys 3. To apply the sampling strategy as developed in Objective 2 in the following two years, to provide relative estimates of the recruitment rates for Snapper in NSG and NGSV Read moreRead less