Catch susceptibility and life history of barred javelin (Pomadasys kaakan) in north eastern Queensland, Australia
Szczecinski, Natasha (2012) Catch susceptibility and life history of barred javelin (Pomadasys kaakan) in north eastern Queensland, Australia. Masters (Research) thesis, James Cook University.
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Abstract
The recreational fishery in Australia is an important part of the country's economy and culture. However, broad spatial and temporal monitoring schemes that are currently used to estimate effort and catch of the recreational fishing sector are insufficient for sustainable management. Often species-specific information is unavailable due to identification problems, as well as area and time specific fisheries (pulse fisheries) which are not identified. This dissertation aims to evaluate current monitoring and management schemes for the fishing industry by (1) developing a profile of a community experiencing seasonal fluctuations in fishing effort, (2) identifying the harvest and life history characteristics of a primary target species, the barred javelin (Pomadasys kaakan) as they apply to the commercial and recreational fishing sectors, and (3) use this information in a Biological Reference Point model to predict the productivity of P. kaakan and assess the effectiveness of recent management changes.
Currently, communities which experience fluctuations in fishing effort due to the seasonal movements of anglers are unrecorded. Lucinda, a community in northeast Queensland, experiences fluctuations of tourist visitation which coincides with changes in fishing catch and effort within the local region. The demographic characteristics and motivations of the tourists visiting Lucinda, as well as a harvest description of the recreational sector, are described in this dissertation. This will demonstrate the importance of identifying communities affected by fishing pressures and the possible impact anglers are having on coastal ecosystems.
A biological description of catch characteristics for the commercial and recreational sector is also required for key species. Updated life history characteristics, including growth parameters and reproductive behaviours, are necessary for use in management plans which keep the collective industry sustainable. For this dissertation, key life history characteristics were defined for Pomadasys kaakan. These data were used in the Spawning Potential Ratio model, with catch characteristics for each sector, to evaluate historical and current minimum size limit laws, as well as the gear selectivity influences of both fishing sectors.
Demographic and motivational profile data was collected using on-site, access point surveys at the main boat ramp in Lucinda and face-to-face surveys of tourists in the local caravan park – Wanderer's Holiday Village. This data were also used to create a harvest description for recreational anglers in Lucinda. Biological samples of P. kaakan were collected from fishery dependent sources, including recreational and commercial fishers. These samples were used to define age and growth parameters, as well as reproductive characteristics.
A definable, seasonal recreational fishery was identified in Lucinda with a 500% increase in fishing effort during the winter months. This fishery was driven by the movement of grey nomads, i.e. senior citizens who travel for prolonged lengths of time in a specific area. The social motivation of travel linked to fishing indicates declines in fishery stock and changes in management may have no effect on return visits to Lucinda and continued participation in fishing. In addition, a high level of targeting behavior was focused on Pomadasys spp. This exemplifies the need for regionally specific monitoring and management plans which sustain the industry and the community.
A comparison of the harvest of P. kaakan for the commercial and recreational sector indicated a higher impact by the recreational sector for this species. The recreational sector has higher harvest rates, targets fish over a broad length range and has a high female sex bias. However, the combined impacts of the commercial and recreational sector, as indicated by the SPR model, had the largest impact on the future productivity of the species. The high female bias in the harvest of P. kaakan in Lucinda also suggests sexual segregation may occur in the Hinchinbrook Channel. This may make the population more susceptible to overexploitation.
As a result of these findings, management may need alternative methods to achieve sustainability goals. Controls on total effort, not individual angler impacts, need to be implemented for effective management. In addition, continued monitoring coupled with a dynamic approach to regulating changes in effort is needed to maintain the status of regional populations. Further research regarding post-release mortality and identification of spawning aggregations are suggested in this dissertation to further assist management with development of future plans.
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