MIXED-SPECIES YIELD-PER-RECRUIT SIMULATIONS OF THE EFFECT OF SEASONALCLOSURE ON A CENTRAL QUEENSLAND COASTAL PRAWN TRAWLING GROUND

An assessment of the effect of seasonal closure on the central Queensl and coastal prawn trawling grounds was carried out by mixed-species yi eld-per-recruit simulations of the fishery based on parameters determi ned from field studies and analysis of logbook data. Under a conventio nal scenario of constant fishing mortality, simulations suggest little positive effect on yield to be achieved from closures of up to 15 wk in duration. Economic gain would have to be made via reduced costs dur ing the closure, rather than through increased value of the postclosur e yield. Logbook data clearly showed that the fishery underwent a heav y pulse of effort, immediately after the fishing season opened. Nonloc al boats had entered the fishery to take advantage of the prawns avail able. Using this more realistic regime of fishing mortality, simulatio ns suggest a significant increase in yield and value of catch. The inc rease was caused by boosted exploitation rates of the stocks and was d etermined by the magnitude of the effort pulse rather than as a direct benefit of the closure.