Stock enhancement of the Western School Prawn (Metapenaeus dalli) in the Swan-Canning Estuary; evaluating recruitment limitation, environment and release strategies
Predicting the impacts of shifting recreational fishing effort towards inshore species
Recreational exploitation of inshore, marine fishes near Perth, WA, including King George Whiting, some other whiting species and Silver Trevally, is likely to increase markedly because of effort transfer from offshore to inshore species, due to new fishing regulations to protect offshore demersal species. No reliable stock assessment information is currently available for any of these species, which may already be overexploited. Furthermore, for King George Whiting and Silver Trevally, current assessment methods are inadequate because offshore movements with increasing body size, combined with different catchabilities and fishing pressures in nearshore and offshore habitats, make it impossible to obtain a representative age composition sample for an overall stock of these species. This problem can be addressed through developing a new stock assessment approach for such species, which is also applicable to other recreational, and commercial species, e.g. Estuary Cod.
The biological information published in reports and papers on commercial and recreational fish species in south-western Australia is often inaccessible to fishers and researchers may not be aware of all available information for those species. A book explaining the basics of fisheries science and outlining key information for important temperate WA fish species would be invaluable for engaging fishers and a valuable reference for researchers and managers.
The proposed project directly addresses an urgent need of the Department of Fisheries, WA, and the recreational sector, to assess likely impacts of recreational effort transfer from offshore to important inshore species. The assessment approach and guide is also very relevant to the commercial sector.
Final report
The project outputs have led to the following outcomes:
1. A model has been developed enabling reliable estimation of mortality of fish species that undertake size-related, unidirectional, offshore movements from age and length data. This new modelling approach is likely to be applicable to stocks of a number of fish species with this life history attribute, for which current stock status information may be very limited due to the difficulty of obtaining a representative sample for an overall stock.
2. Current age and length composition data and estimates of key stock assessment parameters, including selectivity, movement and fishing mortality, are now available for Silver Trevally and King George Whiting in coastal waters near Perth in Western Australia. Managers are aware that the study results have provided preliminary evidence that Silver Trevally and King George Whiting in waters near Perth are not currently experiencing overfishing.
3. This project has provided managers with information about the relative extents to which the stocks of Silver Trevally and King George Whiting in coastal waters near Perth might be expected to be impacted if fishing pressure were to increase by specified amounts. Managers are thus aware that King George Whiting stocks are likely to be more vulnerable than Silver Trevally to increases in fishing pressure in inshore waters.
4. Detailed summaries of the biology, stock assessment and management for 30 of Western Australia’s most important and/or well-known temperate fish species are now accessible to fishery stakeholders in the form of a species guide (published separately as Fisheries Research Report No. 242 by the Department of Fisheries, Western Australia). The guide provides a comprehensive “go to” source of information for anyone who wishes to find key facts and/or literature relating to these species.
Keywords: Silver Trevally, King George Whiting, size-related movement, fishing mortality, uncertainty, model assumptions
Informing rick assessment through estimating interaction rates between Australia sea lions and Western Australia's temperate demersal gillnet fisheries
Australia’s only endemic pinniped, the Australian sea lion (ASL) Neophoca cinerea, is one of the rarest sea lions (~ 14,700) worldwide and listed as “threatened” under Australian Commonwealth legislation and as “Specially Protected Fauna” under the WA Wildlife Conservation Act.
There is considerable concern among some researchers and community sectors that incidental bycatch of ASLs by commercial gillnetting may be preventing the recovery of ASL populations from their current depleted states. Goldsworthy et al (2010) recently estimated that several hundred ASLs die annually in SA due to gillnetting, indicating that there is an urgent need to explore the extent to which ASLs in WA are affected by commercial gillnetting.
WA temperate gillnet fisheries will soon commence Marine Stewardship pre-assessment and their members are acutely aware of the urgent need for research on ASL/gillnet interactions in WA, without which, they cannot achieve certification and are vulnerable to the Commonwealth’s Marine Park planning process (if that process is not based on sound information).
As the distribution of ASL colonies, foraging areas of ASL individuals, and of gillnet fishing in WA are very different from SA, the results of the SA study cannot be applied directly to the WA situation.
Goldsworthy et al. (2009) based their analyses on distance from colonies and depth, but possibly because of limited tagging and/or observer data, did not consider the direction of ASL foraging trips from breeding colonies and haul out points and may have thus overestimated ASL mortality rates due to commercial gillnetting. The accuracy of estimates of ASL/gillnet interactions has major implications for both the conservation of ASL populations and for the viability of important fisheries. Developing improved methods of analysis, e.g. the agent-based modelling approach proposed here, and comparison of results with those from existing approaches are key to facilitating sound risk assessments.
Final report
People Development Program: 2009 FRDC International travel bursary Ben Chuwen
The Australian fishing industry requires the development of people that will assist in ensuring the sustainability of Australia’s fish resources. Such development must include aspects that will enhance leadership capabilities, industry capacity and the transfer of knowledge throughout the sector. One of the most important aspects of fisheries biology is the ageing of fish for use in fisheries management plans. This is a rapidly expanding area of research and leading scientists convene each 4-5 years to present and discuss recent developments in this field, with the 4th International Otolith Symposium to be held in Monterey, California in August 2009. Murdoch University’s Centre for Fish and Fisheries Research is Western Australia’s peak fisheries research training centre and thus it is necessary for staff to continue to be skilled in the most up-to-date techniques and methodology to enable the centre’s high calibre training to continue. My attendance at the 4th International Otolith Symposium is thus important not only for personal professional development, but also for the development of future fisheries researchers in Western Australia.
Establishment of self-sustaining facility for fisheries modelling and multivariate analysis, and for effective management of extremely large fisheries databases.
Coastal development, marine park reservation and population growth, coupled with use of remote sensing technologies, require a range of complex analyses, covering stock assessments and evaluation of ecosystem-wide impacts on fish communities and fisheries. Independent advice relating to compensation and marine park planning and reservation, with triple bottom line reporting needs, is also required. The demand for fisheries scientists with strong quantitative ability has been driven even further by the increasing use of detailed spatial data relating to fish, fisheries and the environment.
Currently, the PhD program in Quantitative Marine Science offered by CSIRO Marine and the University of Tasmania appears to be the only facility established specifically to produce fisheries scientists with the necessary quantitative skills. However, the demand cannot be met by this program alone. There is an urgent need for another university facility within Australia, particularly on the western side of the continent, to complement the training offered by the University of Tasmania in developing the skills in fisheries and ecosystem modelling, stock assessment, multivariate analysis and data management that are now required.
Short courses need to be delivered, on an ongoing basis, to upgrade the skills of existing fisheries scientists, empowering them to deliver answers to the range of policy questions now posed.
Postgraduate and in-service training need to be adaptive, but capable in the short term of delivery on-line throughout Australia, targeted to the specific needs of fisheries scientists, marine ecologists and the fishing industry. With the emergence of new technologies, ongoing course development, the application and use of very large databases using super computers, and implementation of new modelling tools, are essential requirements of this proposed facility.
Seed funding will be required to attract an appropriately qualified scientist to lead the development and ensure the establishment of such an ongoing training facility for Australia.
Final report
Tactical Research Fund: Assessing alternative fishing seasons for red-legged banana prawns in the Joseph Bonaparte Gulf and future directions for collaborative research for NPF Industry Pty Ltd
Until recently management of prawns in the Joseph Bonaparte Gulf (JBG) has been a “byproduct” of measures designed for other NPF stocks. In recent years, the JBG has been fished with the two seasonal openings (April to June, August to November), however in 2007 this arrangement changed, and fishing has only been allowed August to November. The rationale of this change was to see if average size of prawns, and total value of the catch could be increased. However, no clear objectives, performance measures or monitoring system were established to evaluate whether this was achieved.
Little targeted research has been carried out on red-legged banana prawns (Penaeus indicus), the main JBG species. In recent years only rudimentary catch and effort, and commercial grading data have been collected. Even this has not been subject to systematic analysis. In these circumstances anecdotal accounts of recent trends can be argued to support five plausible explanations with differing management implications:
1. The late season has optimized value of production.
2. Value is being forfeited because the season is too late and peak annual biomass is being missed.
3. Value is being forfeited because poor weather late in the year and other fishing commitments prevent limit boats days in the JBG.
4. The late season intensifies fishing on the aggregated spawning biomass risking recruitment over-fishing.
5. Natural variability has produced lower catches than normal.
The NPF Industry Pty Ltd needs its discussion of management in the JBG, and other localized stocks, to be based on sound scientific data. The immediate need is to provide a scientific basis for discussions about the 2010 season, which will occur in late 2009. The medium term need is for NPF Industry Pty Ltd develop its capacity to conduct cost-effective data collection programs.
Final report
To enhance its profitability, NPF Industry Pty Ltd needs to develop its capacity to gather key stock status data for each of its stocks so that simple bio-economic models can be developed and used to assess and potentially optimize the value of component NPF stocks. The NPF Industry Pty Ltd needs its discussion of management policy for localized stocks to be based on sound scientific data. This project started developing the capacity of NPF Industry Pty Ltd to support science based discussions of management by synthesizing the existing data for the red-leg banana prawn (Penaeus indicus) stock in the Joseph Bonaparte Gulf (JBG) and developing initial, simple bioeconomic models for the stock.