General Discussion – Torres Strait prawn project

General Discussion. R. Watson, (1990). “General Discussion.,” Torres Strait prawn project: A review of research 1986-88 (Queensland Fisheries, Brisbane, Australia). Chapter 13.

This report presents some of the results from three years of research in Torres Strait. Some of the sections cover research which is presently ongoing and therefore are truly provisional in nature, while other sections have been reported in full as those phases of our research are completed. All sections presented in this interim report are esselltial to meeting our project’s objectives {Section 1 ), as we could not restrict our research to surveys of adult commercial catches and historical studies of the fishery. It was necessary to study aspects of adult reproduction and juvenile development and to initiate tagging studies to understand and elucidate the life-cycle of the commercial prawn species Tagged prawns also allowed migration and growth rates to be monitored. It was necessary to investigate the use and performance of various survey gear to quantify estimates of juvenile and adult prawn numbers. Though this work was not an end in itself, it increased our understanding of prawn behaviour and revealed the potential sources of error in our survey estimates. Velvet prawns are not fished commercially in Torres Strait as they are in other north Queensland fisheries. We included them in our study for a two-year period because they were numerous, they are important to many other fisheries in the Indo-Pacific region, and they are of potential commercial value in Torres Strait. This work is now complete and it greatly increased our understanding of these species. Our surveys for juvenile prawns in seagrass areas often captured large numbers of other species, most notibly smaller fish species. Some of these are known to be major predators of juvenile commercial prawns. By retaining these fish specimens from beam trawl samples we were able to greatly expand our knowledge of potential prawn predators and of the community structure of seagrass habitats. Gathering information on the basic biological parameters of the commercial prawn species is time consuming. Often there is no completely satisfactory way of assessing the precision of our estimates of important things such as growth rates. A few years study of such a complex system as the Torres Strait Prawn Fishery does not allow much insight into the variability of these parameters between areas, years, and sometimes species. Though there is a strong desire for us to continue to improve our estimates and our understanding of the processes involved, this refinement would ultimately occur at the expense of our commitment to fisheries managers who require information on the relative merits of management options in real time. Key biological or population parameters can be combined with historical data in new or existing models of the fishery. The creation of these models test our understanding of the system. Our models can be refined as our understanding develops and through this process we can redirect our existing research to gather further information on key parameters or processes, or initiate research on important components that have been overlooked. We can use our models to test the possible impacts of different management scenarios once our models adaquately represent our understanding of the system and produce predictions which can be verified. Though the model predictions can often not be tested directly, they nevertheless represent our best estimate of the possible outcome of a management measure given our understanding of the fishery. In this way we can provide fisheries managers with the best information possible on which to base management decisions.