Snapper Science Program: Theme 1 - Biology And Ecology
Funder
Fisheries Research and Development Corporation
Funding Amount
$1,982,523.00
Summary
A comprehensive understanding of the general biology and ecology of any fishery species is fundamental to determine its response to exploitation and inform appropriate fishery management. Despite the significant body of research into the biology of Snapper, there remain considerable knowledge gaps regarding the underlying factors that drive interannual variation in juvenile recruitment and the demographic processes that maintain populations. Furthermore, there is uncertainty in how these process ....A comprehensive understanding of the general biology and ecology of any fishery species is fundamental to determine its response to exploitation and inform appropriate fishery management. Despite the significant body of research into the biology of Snapper, there remain considerable knowledge gaps regarding the underlying factors that drive interannual variation in juvenile recruitment and the demographic processes that maintain populations. Furthermore, there is uncertainty in how these processes will be influenced by changing environmental conditions associated with climate change. As such, understanding drivers of recruitment variability was identified as one of the highest research priorities for Snapper at the most recent National Workshop (FRDC Project No. 2019-085; Cartwright et al. 2021). Given the strong relationship between episodic recruitment and fishery production described above for the SG/WCS and GSVS, this recommendation was also strongly endorsed by fishery researchers, managers, and industry stakeholders in SA (Drew et al. 2022).
This research proposal has been developed to address four research priorities: • To understand the biological and environmental factors that affect recruitment of Snapper in SA and evaluate the potential influence of climate change. • Provide a contemporary understanding of stock structure for Snapper on the west coast of Eyre Peninsula to inform the appropriate spatial scale for fishery management. • Develop a contemporary series of biological parameters for each stock of Snapper in SA to be used as inputs in the stock assessment model. • Evaluate changes in the physical environment that may affect Snapper recruitment.
Consequently, Research Theme 1 – Biology and Ecology involves four projects: 1.1 Investigating recruitment variability and evaluating the potential effects of climate change for Snapper in South Australia 1.2 Contemporary demographic processes and stock structure for Snapper on the west coast of Eyre Peninsula 1.3 Review of biological parameters for Snapper in South Australia 1.4 Benthic habitat survey for Gulf St Vincent.
1.1 Investigating recruitment variability and evaluating the potential effects of climate change for Snapper in South Australia The population dynamics and fishery productivity for Snapper in SA are fundamentally driven by highly variable interannual recruitment, i.e., the number of age 0+ juveniles that enter the population each year (Fowler et al. 2017, Fowler and Jennings 2003). As such, a relative index of annual age 0+ juvenile abundance would be a powerful, fishery-independent tool to predict future trends in fishable biomass. To address this need, a recent project was undertaken to identify the most appropriate sampling methodology for age 0+ Snapper in SA’s gulfs and to develop a pre-recruit index (FRDC Project No. 2019-046). The first component of the present study involves the continuation of annual surveys for age 0+ Snapper for each stock to monitor trends in juvenile recruitment. The surveys will be repeated annually at the recognised nursery areas for each stock, i.e., northern Spencer Gulf (NSG) for the SG/WCS and northern Gulf St Vincent (NGSV) for the GSVS (Fowler et al. 2017). In addition, age 1+ juvenile Snapper will be sampled from annual fishery-independent surveys for the Spencer Gulf and Gulf St Vincent prawn fisheries, which will provide further information to determine relative year class strength.
The second component of the study involves investigating the relationships between environmental parameters and recruitment. The datasets for juvenile abundance will be considered with annual population age structures to develop a time series of recruitment for the two stocks (i.e., late 1960s to 2020s). Long-term time series of environmental parameters (e.g., temperature, salinity, productivity, wind stress) will be developed and compared to the time series of recruitment for each stock. In conjunction with the pre-recruit index, understanding the environmental influences that drive recruitment variability would provide even greater predictive capability to forecast trends in recruitment and fishable biomass, particularly under changing environmental conditions associated with climate change.
The third component of the study will investigate the potential effects of environmental change for Snapper in SA. Using the environmental datasets previously developed, a high-resolution oceanographic model for SA will be hindcast to determine the intensity of local environmental change and identify potential climate ‘hot spots’. The model will then be forecast with different climate change scenarios to predict changes in ocean conditions over the next 5, 10, and 50 years. Based on the physiological tolerance ranges for Snapper spawning and larval development, these predictions will be used to evaluate potential shifts in the availability of suitable environmental conditions for Snapper in SA. Such responses will be considered in terms of potential implications for future trends in recruitment and fishable biomass.
1.2 Contemporary demographic processes and stock structure for Snapper on the west coast of Eyre Peninsula There are three recognised stocks of Snapper in SA waters: the SG/WCS, the GSVS, and the Western Victoria Stock (WVS) (Fowler 2016, Fowler et al. 2017). The population of Snapper on the West Coast of Eyre Peninsula (WC) is a regional component of the SG/WCS. It is hypothesised that in most years, the WC population is replenished by local demographic processes that maintain the population at a relatively low level. However, episodically in years of exceptionally strong recruitment in northern Spencer Gulf (i.e., 1991, 1997, and 1999), the WC population is replenished through the density dependent emigration of fish of a few years of age that disperse from northern Spencer Gulf, through southern Spencer Gulf and to the WC. These fish then remain on the WC for the remainder of their lives.
As a consequence of the prolonged period of poor recruitment in northern Spencer Gulf since 1999 and the subsequent depletion of the population in Spencer Gulf, it is unlikely that this density dependent movement from Spencer Gulf to the WC has occurred to a major extent for a number of years or will occur until the Spencer Gulf population has recovered. Furthermore, age structures for the WC developed in 2020 and 2021 showed that only a very small number of fish from the strong 1997- and 1999-year classes in northern Spencer Gulf remained in the population, and there were several other year classes in the age structures for the WC that were not present in northern Spencer Gulf (Drew et al. 2022). Consequently, there is a need to understand the relative contributions of local population processes and emigration from northern Spencer Gulf to the WC population. This is particularly important following the regionalisation of the fishery through the Marine Scalefish Fishery (MSF) Reform (Smart et al. 2022).
This study will investigate the contemporary demographic processes that maintain the population of Snapper on the WC through the regional comparison of population age structures, elemental chemistry of otoliths, and population genomics. The findings will provide insight into the relative contributions of local recruitment and emigration to the WC population, that will be compared to the existing conceptual model of stock structure for Snapper in SA (Fowler 2016, Fowler et al. 2017). The proposed study will build on several previous projects that have investigated the stock structure of Snapper in SA (i.e., FRDC Project No. 2002-001, FRDC Project No. 2012-020, ARC Linkage Project No. LP180100756).
1.3 Review of biological parameters for Snapper in South Australia The biology of Snapper in SA has been studied over the past 40 years, with particular focus on northern Spencer Gulf (e.g., Jones 1981, 1987, McGlennon 2003). Since 2000, a weekly market sampling program has been undertaken by SARDI researchers that has provided biological data for Snapper caught by commercial fishers across SA. The sampling program has been augmented with periodic trips to regional areas, research cruises, and targeted research projects. Since the closure of the SG/WCS and GSVS in November 2019, biological samples from the two stocks have been accessed through a targeted sampling program which involved contracting commercial fishers. The data collected through these projects and programs is maintained in a MS Access database which currently contains biological information (i.e., capture date, location, length, weight, sex, reproductive stage, and age) for >27,000 Snapper and length information for >75,000 individuals.
This study will investigate potential changes in the biological characteristics of Snapper throughout SA over the past 40 years in response to temporal changes in environmental conditions and stock abundance. This will involve spatial and temporal comparisons of length, age, growth rate, and length at maturity for Snapper from each region of SA. The study will also consider various approaches to estimate natural mortality. A key output of the study is a summary of contemporary biological parameters for each stock of Snapper in SA that will be incorporated into the stock assessment model (‘SnapEst’).
1.4 Benthic habitat survey for Gulf St Vincent Snapper utilise a diversity of different benthic habitats throughout its life history, ranging from soft sediments that are favoured by recently settled juveniles to high relief structures that act as aggregation sites for spawning adults. As a result of the significant interannual variation in recruitment observed for Snapper in SA and the subsequent development of a pre-recruit index, there is particular interest in the spatial distribution and relative abundance of benthic habitats that act as nursery areas for age 0+ juvenile Snapper. In order for the pre-recruit index to provide reliable estimates of annual recruitment, it is essential that the key areas which support 0+ Snapper are sampled consistently each year.
In the recent project to develop a pre-recruit index (i.e., FRDC 2019-046), sampling for 0+ juvenile Snapper was targeted at the hypothesised nursery areas for each stock, i.e., northern Spencer Gulf (NSG) for the SG/WCS and northern Gulf St Vincent (NGSV) for the GSVS (Fowler et al. 2017). For NSG, the sampling design was informed by the results of annual surveys in the region from 2000 to 2010, which identified a strong relationship between the spatial distribution and abundance of 0+ Snapper and localised areas of soft, silty benthic substrate (Fowler and Jennings 2003, Fowler et al. 2010). There were no previous surveys for 0+ Snapper in NGSV, and therefore sampling locations were determined by the presence of suitable benthic substrate from existing habitat studies (Shepherd and Sprigg 1976, Tanner 2002). However, from 2021 to 2023, the catches of age 0+ Snapper in NGSV were very low in each annual survey and it cannot be determined if this reflected poor juvenile recruitment in these years, or if key nursery areas were not adequately sampled.
The aim of this study is to quantify the spatial distribution and relative abundance of benthic habitats in GSV, with particular emphasis on localised areas of soft substrate that may support age 0+ juvenile Snapper. The study will use towed underwater video and particle size analysis of sediment samples to quantify habitat types at ~150 sites throughout GSV following the methods recently applied in Spencer Gulf (FRDC 2020-002; Grammer et al. in prep.). The spatial distribution and relative abundance of benthic habitat types identified in this study will be compared to previous surveys in 1964-69 (Shepherd and Sprigg 1976) and 2000-01 (FRDC Project No. 1998-208; Tanner 2002) to assess changes in benthic habitats in GSV over the past 50 years, and how such changes may relate to trends in recruitment and stock abundance for Snapper over this time.
Objectives: 1. Quantify the abundance of age 0+ Snapper in northern Spencer Gulf and Gulf St Vincent to provide relative estimates of recruitment for 2024, 2025, and 2026. Examine the otoliths of these fish to improve the understanding of early life history processes. 2. Evaluate the relationships between environmental parameters and recruitment variability for Snapper in South Australia and evaluate the potential effects of environmental change on spawning and recruitment. 3. Determine the contemporary demographic processes that maintain Snapper populations on the west coast of Eyre Peninsula, i.e., local recruitment vs. emigration from adjacent regional populations, and to use this information to assess stock structure. 4. Assess possible changes in key biological parameters of Snapper for each stock in South Australia in response to temporal changes in environmental conditions and stock abundance. 5. Quantify the spatial distribution and relative abundance of benthic habitats utilised by juvenile Snapper in Gulf St Vincent and assess potential changes over the past 50 years. Read moreRead less
ARC Centre of Excellence for Climate Extremes. This Centre aims to transform understanding of past and present climate extremes and revolutionise Australia’s capability to predict them into the future. Climate extremes cost Australia up to $4 billion a year and will intensify over coming decades. This Centre’s blue-sky research will discover processes that explain the behaviour of present and future climate extremes. It will use its researchers, data, modelling, collaboration, graduate programme ....ARC Centre of Excellence for Climate Extremes. This Centre aims to transform understanding of past and present climate extremes and revolutionise Australia’s capability to predict them into the future. Climate extremes cost Australia up to $4 billion a year and will intensify over coming decades. This Centre’s blue-sky research will discover processes that explain the behaviour of present and future climate extremes. It will use its researchers, data, modelling, collaboration, graduate programme and early career researcher mentoring to transform Australia’s capacity to predict climate extremes. This research is expected to make Australia more resilient to climate extremes and minimise risks from climate extremes to the Australian environment, society and economy.Read moreRead less
Southern Ocean aerosols: sources, sinks and impact on cloud properties. This project aims to provide fundamental process-level understanding of atmospheric aerosol processes over the Southern Ocean, a region that has a profound influence on the Australian and global climate and where climate models perform poorly. Comprehensive observations during 3 Southern Ocean voyages and land-based measurements will enhance our knowledge of aerosols and cloud formation in that region and provide much-needed ....Southern Ocean aerosols: sources, sinks and impact on cloud properties. This project aims to provide fundamental process-level understanding of atmospheric aerosol processes over the Southern Ocean, a region that has a profound influence on the Australian and global climate and where climate models perform poorly. Comprehensive observations during 3 Southern Ocean voyages and land-based measurements will enhance our knowledge of aerosols and cloud formation in that region and provide much-needed data for improving global climate models. Expected outcomes include more accurate seasonal and latitudinal representations of Southern Ocean aerosol populations, properties and sources. The main benefit includes improvements in weather forecasting and future climate projection for Australia and the Southern Hemisphere.Read moreRead less
Can Spatial Fishery-dependent Data Be Used To Determine Abalone Stock Status In A Spatially Structured Fishery?
Funder
Fisheries Research and Development Corporation
Funding Amount
$562,128.00
Summary
With the advent of the Status of Australian Fish Stocks (SAFS) process, there is now a requirement to provide a stock ‘status’ determination in addition to the annual TACC determination. The ‘status’ reflects changes in the overall biomass, the fishing mortality, or in their proxies. This has led to disagreements among researchers, managers and industry, largely due to uncertainty around how best to derive a meaningful overall stock status indicator to meet the requirements of the SAFS reporting ....With the advent of the Status of Australian Fish Stocks (SAFS) process, there is now a requirement to provide a stock ‘status’ determination in addition to the annual TACC determination. The ‘status’ reflects changes in the overall biomass, the fishing mortality, or in their proxies. This has led to disagreements among researchers, managers and industry, largely due to uncertainty around how best to derive a meaningful overall stock status indicator to meet the requirements of the SAFS reporting process. These higher-level reporting processes are an important demonstration of sustainable management of Australian fisheries, but only if stock status determinations are accurate and defensible.
Australian abalone fisheries primarily use harvest control rules based around CPUE (Kg/Hr) to set TACC. However, with abalone, stable catch-rates may not indicate stable biomass and/or stable density. Catch-rates are frequently criticised because the effort needed to take a quantity of catch may be influenced by density but also by density independent factors such as conditions at the time of fishing, experience, and the ability of fishers to adjust their fishing strategy to maintain catch rates (diver behaviour driven hyper-stability). While there are many issues with the assumption that CPUE is a reliable proxy for abundance, it is assumed to be so despite the absence of robust data to validate use of CPUE in this way. In some jurisdictions CPUE is supplemented by sparse fishery-dependent size and density data. There is an urgent need to review common assumptions, methods and interpretations of CPUE as a primary indicator, and to determine whether inclusion of spatial fishery data could provide a ‘global’ indicator of stock status for abalone fisheries.
Objectives: 1. Characterise the statistical properties, coherence, interpretability and assumptions of spatial and classic indicators of fishery performance 2. Develop methods for inclusion of fine-scale spatial data in CPUE standardisations 3. Identify methods for detecting hyper-stability in CPUE 4. Determine feasibility of spatial data based stock status determination in spatially structured fisheries Read moreRead less
Laying The Foundation For Mulloway Stock Recovery Through Filling Critical Knowledge Gaps And Modelling.
Funder
Fisheries Research and Development Corporation
Funding Amount
$1,299,348.50
Summary
Critical knowledge gaps identified by the cross-sectoral harvest strategy working group are encapsulated within three priority areas for mulloway in NSW:
1) Information on the spatial extent of population structure
Whilst mulloway in NSW have been shown to be part of a single genetic stock along the east coast (Barnes et al. 2015), which is managed at the jurisdictional level (Queensland, New South Wales, Victoria – Earl et al. 2021), the overall general small scales of movemen ....Critical knowledge gaps identified by the cross-sectoral harvest strategy working group are encapsulated within three priority areas for mulloway in NSW:
1) Information on the spatial extent of population structure
Whilst mulloway in NSW have been shown to be part of a single genetic stock along the east coast (Barnes et al. 2015), which is managed at the jurisdictional level (Queensland, New South Wales, Victoria – Earl et al. 2021), the overall general small scales of movement and connectivity (Hughes et al. 2022), and spatial variation in otolith chemistry (Russell et al. 2021), suggest the potential for fine-scale population structuring within the broader stock. Such population structuring may occur over various time scales (e.g. evolutionary, generational or lifetime) relevant to management of the species. Identifying the spatial extent of population structure is therefore critical to inform the potential utility of spatially structured monitoring, assessment, and management of the species in NSW, including the potential need for cross-jurisdictional collaboration with Queensland and Victoria.
2) Refined and updated population life-history parameters
As described above, evidence indicates the potential for fine-scale within-generation population structure of mulloway within NSW, as has been demonstrated elsewhere in Australia (Ferguson et al. 2011). For mulloway in NSW, sub-populations may be subject to variation in environmental variables (e.g. habitat, water temperature, salinity), particularly those that vary with latitude. Such population structure may therefore manifest itself in spatial variability in demographic characteristics, such as growth, size and age composition, and mortality that affect stock productivity and subsequent resilience to exploitation. Information on mulloway reproductive biology was collected in the early 2000s and established size- and age-at-maturity (Silberschneider & Gray 2005), however information on the spatial and temporal extent of spawning is not clearly defined and the body-size fecundity relationship for mulloway in NSW is not well known. An updated examination of spatial variation in size and age structures, growth, mortality and reproductive biology are therefore urgently required to underpin length- and age-based components of future stock assessments for mulloway in NSW.
3) Assessment of gear selectivity and discard/release mortality for the main fishing methods.
Despite the majority of the commercial mulloway catch (~60%) being taken using gillnets (termed ’mesh nets’) in NSW, to date there has been very little research into selectivity, bycatch, discarding and post-release mortality of mulloway caught in this gear. Research on discard (‘release’) mortality from recreational fishing has shown that the two key predictors of mortality are deep-hooking (Butcher et al. 2007) and barotrauma (Butcher et al. 2013, Hughes et al. 2019), however, most of this work was restricted to small mulloway (< 45 cm TL) and no data are available on the fate of larger angled and released conspecifics. Research into the selectivity, rates of discarding and unaccounted fishing mortality of mulloway caught in the main gears and sectors are therefore urgently required (e.g. by defining selectivity functions and rates of discarding and post-release mortality for use in future stock assessment models).
Other knowledge gaps fall under priority areas already being addressed by existing NSW DPI-Fisheries initiatives (e.g. improved fishery data from all sectors, development of fishery-independent survey methods and updated comprehensive ERA; Figure 1).
Successfully fulfilling all knowledge gaps will generate data that will underpin a fourth priority area:
4) Development of a dynamic population model.
This is the essential tool that will be developed to reduce uncertainty in the species stock assessment, service the requirements of the harvest strategy to rebuild the stock, and guide future management to maintain the stock at a level that improves access to, and use of, the resource by all sectors. Any model(s) must also support an expandable assessment approach, capable of determining stock status with reasonable confidence from limited data available during the stock rebuilding phase, but with the ability to integrate additional data sources as they become available (once the rebuilding phase is complete) and maintaining continuity with previous assessments. The role of climatic/environmental drivers on mulloway population dynamics will also be examined within the integrated assessment model(s) that will be developed.
Without the improved knowledge encapsulated in the above priority areas for research, any reasonable assessment of the status of the resource, estimation of appropriate harvest levels, harvest strategy development, and implementation of appropriate management to rebuild the resource and maintain sustainability in future, will not be possible. This will in turn directly impact the magnitude, profitability, and social outcomes derived from the resource. Funding from the FRDC is therefore needed to address these key identified knowledge gaps, representing an urgent research priority for all harvesting sectors of the resource in NSW. Objectives: 1. 1. Resolve the fine scale population structure for mulloway in south-eastern Australia (southern Queensland, New South Wales and eastern Victoria). 2. 2. Refine and update population life-history parameters (demographic and reproductive information) from across the spatial extent of the stock. 3. 3. Assess selectivity and discard/release mortality for the main gears and sectors (gillnets and angling), and develop approaches to minimise mortality. 4. 4. Integrate information generated from objectives 1–3 and data collected by existing monitoring programs, and develop a dynamic population model(s) to support future stock rebuilding strategies for the NSW mulloway population. Read moreRead less
Abundance, Population Modelling, And Potential Biological Removal Estimates For Common Dolphins In Spencer Gulf: Implications For The South Australian Sardine Fishery
Funder
Fisheries Research and Development Corporation
Funding Amount
$380,000.00
Summary
This project is needed to assess the impacts of the South Australian Sardine Fishery (SASF) on the common dolphin (Delphinus delphis). The SASF is Australia’s largest volume fishery and is critical to providing a supply of feed for the ranching of southern bluefin tuna. Operational interactions between common dolphins and the SASF have been persistent since the development of the fishery. Common dolphins occasionally become encircled in purse seine nets during fishing operations, which can lead ....This project is needed to assess the impacts of the South Australian Sardine Fishery (SASF) on the common dolphin (Delphinus delphis). The SASF is Australia’s largest volume fishery and is critical to providing a supply of feed for the ranching of southern bluefin tuna. Operational interactions between common dolphins and the SASF have been persistent since the development of the fishery. Common dolphins occasionally become encircled in purse seine nets during fishing operations, which can lead to their injury and death. Observations of high interaction rates from an initial observer program, led to the temporary closure of the fishery in 2005 while an industry Code of Practice (CoP) to reduce dolphin interactions was developed. Since then, the CoP has been reviewed and refined to increase its effectiveness in preventing dolphin interactions, and improve release procedures. An independent on-board observer program has operated in the fishery since July 2006. It collects information on dolphin interaction and mortality rates, as well as data relating to the application of the CoP, and this information is provided in annual assessment reports. Since the introduction of the CoP, dolphin encirclement and mortality rates have declined, however, concerns about the level of interactions and mortality have persisted, with industry facing sustained pressure to demonstrate that steps taken to manage and mitigate dolphin interactions represent World’s best practice, and are sustainable.
This project is needed to address Marine Stewardship Council Fishery Assessment recommendations for the SASF to collect adequate and sufficient quantitative information to assess the consequences of interactions with common dolphins on their populations. This project is needed to provide an important Australian fisheries test-case for meeting new US Government legislation, requiring nations importing seafood to demonstrate that they have a regulatory program for reducing marine mammal bycatch that are comparable in effectiveness to US standards. Objectives: 1. Estimate the abundance of common dolphins in core fishing areas of the SASF 2. Collect critical life history (longevity, age specific mortality) information from museum specimens 3. Develop population models to evaluate bycatch limits of common dolphins and assess the sustainability of interactions with the SASF Read moreRead less
Understanding Population Structure And Dynamics Of Victoria’s Developing Octopus Fishery
Funder
Fisheries Research and Development Corporation
Funding Amount
$561,140.00
Summary
In Victoria, Octopus spp. are predominantly a byproduct species caught across various fisheries. Pale Octopus is not differentiated from other octopus species in catch and effort reporting in Victoria, making it difficult to apply stock assessment methods or catch rate indicators. Maori Octopus (Octopus maorum) are likely caught in the Victorian Rock Lobster Fishery (VRLF); whereas Pale Octopus and Gloomy Octopus (Octopus tetricus) are caught within the Inshore Trawl Fishery, Ocean Access Fisher ....In Victoria, Octopus spp. are predominantly a byproduct species caught across various fisheries. Pale Octopus is not differentiated from other octopus species in catch and effort reporting in Victoria, making it difficult to apply stock assessment methods or catch rate indicators. Maori Octopus (Octopus maorum) are likely caught in the Victorian Rock Lobster Fishery (VRLF); whereas Pale Octopus and Gloomy Octopus (Octopus tetricus) are caught within the Inshore Trawl Fishery, Ocean Access Fishery (OAF), Corner Inlet Fishery (CIF) and Port Phillip and Westernport Bay Fishery (PPWPBF). Targeting octopus using 'shelter traps' within the OAF off Lakes Entrance has significantly increased in 2016 and 2017. The average catch during this period was ten times greater compared with the average catch taken from 2006–2015. With the potential for a developing fishery, management is lacking fundamental information to assist in guiding and building a sustainable fishery. For example, there is no requirement to identify and report quantities of species caught. This makes any sort of assessment impossible. Presently, two license holders actively fish for octopus with a capacity to have many more within the OAF. Objectives: 1. Species identification: * Develop identification keys to ensure octopus are identified to at least the three main species and to ensure collection of accurate catch and effort data. 2. Biological characteristics:* Determination of age, growth and reproduction information.* Determine population structure to inform appropriate spatial scale for management. 3. Development of appropriate biomass indicators and analysis for assessment:* Implement pot sampling regime to enhance the understanding of fishery impact particularly at relatively small spatial scales.* Development and assessment of performance indicators to monitor biomass and stock status. 4. Development of fisheries management tools: * Identify appropriate spatial management tools based on stock structure defined in objective 2a. * Identify an objective approach for setting limit and target reference points for the indicators developed in objective 3. * Provide an overview of possible management tools and their suitability for the Victorian octopus fishery given the identified biological characteristics in objectives 1 and 2.* Using a process identified by VFA develop one or more harvest strategy proposals. Read moreRead less
Assessing Egg Oiling As A Long Term Management Tool For Overabundant Silver Gull Populations Interacting With Southern Bluefin Tuna Aquaculture Operations
Funder
Fisheries Research and Development Corporation
Funding Amount
$560,056.00
Summary
Agencies responsible for management of the aquaculture industry in collaboration with industry stakeholders are committed to incorporating principles of Ecologically Sustainable Development (ESD) into aquaculture regulatory processes (Fletcher 2004). One of the key objectives of ESD is "to protect biological diversity and maintain essential ecological processes and life-support systems". Addressing the ecological impacts of an overabundant legacy population of Silver Gulls in close proximity to ....Agencies responsible for management of the aquaculture industry in collaboration with industry stakeholders are committed to incorporating principles of Ecologically Sustainable Development (ESD) into aquaculture regulatory processes (Fletcher 2004). One of the key objectives of ESD is "to protect biological diversity and maintain essential ecological processes and life-support systems". Addressing the ecological impacts of an overabundant legacy population of Silver Gulls in close proximity to tuna operations in Port Lincoln has been identified as a priority by ASBTIA, in consultation with DEW and PIRSA, to address this ESD objective.
The project is a collaboration between resource management agencies and the tuna aquaculture industry in Port Lincoln. It seeks to expand on the research of Harrison (2010) to assess a three-year trial of Silver Gull egg oiling on selected off-shore islands near Port Lincoln and its impact on local reproductive success and population numbers of Silver Gulls. In doing so it aims to assess the efficacy of egg oiling as a possible management technique to control growth of Silver Gull populations and thereby reduce the current detrimental economic, social and environmental impacts associated with recent increases in Silver Gull numbers in the Port Lincoln region.
Information provided through the research project will inform any ongoing monitoring and management of over-abundant Silver Gull populations within the frameworks of the region's National Park Management Plans and within PIRSA Aquaculture policy objectives. The efficacy of egg oiling and indices measured in the project will also be assessed to provide guidance on any future egg oiling management intervention.
Objectives: 1. Undertake a review and Cost Benefit Analysis (CBA) of over-abundant seabird population management strategies. This will be a project Stop/Go point to assess whether egg oiling provides the best management option for Silver Gull population control, and will determine whether the project proceeds as planned. 2. Estimate Silver Gull population size and structure through counts of breeding pairs (nest) and juveniles at up to five islands near Southern Bluefin Tuna aquaculture operations. Compare estimates with historical information for population trend analyses. 3. Obtain estimates of breeding success from oiled (treated) versus non-oiled (control) Silver Gull nests for use in population modelling. 4. Quantify short term effects of egg oiling on juvenile abundance, through measurement of the ratio of juvenile to adult Silver Gulls present at Southern Bluefin tuna aquaculture farms over three years and assess this indicator's efficacy in providing evidence of egg oiling management. 5. Assess Silver Gull breeding schedules, movement and habitat use within the study area. 6. Develop population models to assess the sensitivity of Silver Gull populations to reductions in breeding success from egg oiling and inform ongoing management targets for Silver Gull population numbers. Read moreRead less
Developing An Independent Shallow-water Survey For The Western Rock Lobster Fishery: Tracking Pre-recruitment Abundance And Habitat Change
Funder
Fisheries Research and Development Corporation
Funding Amount
$445,500.00
Summary
The current method of measuring undersize lobster abundance (PRA) is based on catch data adjusted for multiple biases inherent in commercial monitoring, namely: water depth, water temperature, swell, fisher experience, pot type, escape gaps, pot pulling time, month and location. Biases are exacerbated by recent poor sample sizes, as many fishers choose not to fish in shallow-water areas. Developing a standardized, repeatable survey in shallow areas will provide an improved index of PRA that ca ....The current method of measuring undersize lobster abundance (PRA) is based on catch data adjusted for multiple biases inherent in commercial monitoring, namely: water depth, water temperature, swell, fisher experience, pot type, escape gaps, pot pulling time, month and location. Biases are exacerbated by recent poor sample sizes, as many fishers choose not to fish in shallow-water areas. Developing a standardized, repeatable survey in shallow areas will provide an improved index of PRA that can be incorporated into the stock modelling: this would improve the overall assessment. Currently fishery-independent survey data collection requires a minimum of two staff to process the catch and record information. Data entry is conducted by a third staff member. To increase cost effectiveness (for this and other lobster surveys), a more efficient data collection system is needed. Initial scoping has identified a number of possible solutions (e.g. app-based entry). This project will expand on this original scoping work to develop a solution. This will also benefit commercial lobster monitoring work conducted by DPIRD as well as a range of other surveys in similar pot based fisheries. This survey will also provide a platform for monitoring inshore WRL habitats. This will establish a baseline against which further research into the relationships between WRL and their near shore habitats can be undertaken. This will assist with detecting and quantifying habitat shifts that may impact the fishery. For example, there is anecdotal evidence that the heatwave temporarily modified some of these near shore habitats, leading to the altered relationship between puerulus and lobster recruitment. Long-term monitoring of juvenile habitats will likely provide a useful indicator of one of the factors affecting recruitment to the fishery. Objectives: 1. Produce accurate measures of pre-recruit abundance throughout the West Coast Rock Lobster Managed Fishery. Compare with commercial monitoring undersize lobster abundance and puerulus settlement data. 2. Design and construct a more efficient data recording tool to increase the accuracy and speed of data collection. 3. Develop base-line habitat descriptions at all potting locations throughout the shallow water survey. 4. Determine the relationship between sampling rate required to detect different magnitudes of marine habitat change at these survey locations 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