Project number: 1998-130
Project Status:
Completed
Budget expenditure: $94,826.00
Principal Investigator: Jonathan Staunton-Smith
Organisation: Department of Agriculture and Fisheries EcoScience Precinct
Project start/end date: 28 Jun 1998 - 30 Jun 2001
Contact:
FRDC

Need

1. Need to thoroughly assess the developmental fishery
Logistical difficulties encountered during the first year of Queensland's developmental fishery have recently been overcome and levels of effort during the final year seem likely to approach the capacity of the vessel and crew. Extending the research project to include this final year of fishing will facilitate the acquisition of catch-at-age data from the first year of large-scale commercial utilisation of a virtually virgin stock. This will enhance assessment of the fishery’s potential as these data are essential for the application of age-based simulation models (C. Dichmont, pers. comm) that will be used to obtain a preliminary estimate of biomass for comparison with estimates obtained using the DEPM and that may be used for future assessments of the fishery.

2. Need to assess inter-annual variations in stock size
Studies in South Australia and Victoria indicate the potential for large inter-annual variations in the spatial and temporal patterns of distribution and abundance of clupeoid eggs/larvae. These fluctuations, in conjunction with variations in adult spawning parameters and age-specific mortality rates, can greatly affect estimates of spawning biomass obtained using the DEPM and have significant implications for agencies responsible for the management of pilchard stocks. Several scientists (e.g. Dr D Williams, AIMS) have suggested that interannual variations in abundance may be particularly large in locations that are relatively close to the edge of the geographical distribution of pilchards, such as southern Queensland. Quantification of the magnitude of inter-annual fluctuations requires egg surveys to be conducted over several years. Conducting egg surveys during a year of intensive fishing will facilitate the comparison of estimates of spawning biomass obtained using the DEPM with those calculated using fishery-dependent methods (Hilborn and Walters 1992).

3. Need to develop a fishery-independent sampling method
Researchers throughout Australia urgently require an efficient fishery-independent method for collecting the samples of adult pilchards required to monitor seasonal changes in reproductive status and estimate parameters required for application of the DEPM (e.g. K. Jones, M. Kinloch (SARDI), D. Gaughan (WADF) - pers. comm.). The use of a multi-mesh gill net to sample fish attracted to surface and underwater lights was tested from the RV Warrego in October 1997. This method appears to provide a cost and time efficient means of catching adult pilchards but needs to be refined and tested.

4. Need to develop and assess methods to minimise impacts on dolphins
Predatory fishes, seabirds and marine mammals that occur in the waters of southern Queensland appear to feed opportunistically and seem unlikely to be seriously effected by an ecologically sustainable fishery for pilchards. However, the common bottle-nosed dolphin, Tursiops truncatus, is sometimes encircled and occasionally drowned in purse seine fisheries throughout Australia. The occasional capture of such animals in fishing gear must be given due consideration by fisheries managers as conservation groups have recently used this issue as a reason for closing down sustainable fisheries, even when capture rates are so low that impacts on population levels are minimal. The incidental capture of dolphins in purse seine nets in southern Queensland can only be quantified and the need for and/or success of mitigating procedures for use in Australian fisheries can only be properly assessed during an extended period of intensive fishing such as will occur during 1998/9.

Objectives

1. To obtain catch-at-age data from a virgin stock in order to compare estimates of spawning biomass of pilchards obtained using the Daily Egg Production Method (DEPM) and age-based simulation models.
2. To describe the inter-annual variations in the spatial and temporal patterns of distribution and abundance of clupeoid eggs/larvae in southern Queensland and northern NSW.
3. To develop, apply and assess a new technique for obtaining samples of adult pilchards required to (i) obtain fishery-independent estimates of population structure, (ii) describe seasonal changes in reproductive status and (iii) calculate adult reproductive parameters required for application of the DEPM.
4. To develop and assess methods for preventing common bottle-nosed dolphins, Tursiops trucatus, being encircled in purse seine nets.

Final report

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