Evaluating the scientific benefits of spatially explicit experimental manipulations of common coral trout (Plectropomus leopardus) populations on the Great Barrier Reef, Australia

A simulation approach is used to evaluate the likely scientific benefits of experimental manipulation of fishing mortality on the Great Barrier Reef, Australia. The Effects of Line Fishing (ELF) Project commenced in 1994, with the first round of manipulations conducted during 1997-1998. The experimental design involves 24 reefs arranged in four clusters of six reefs spanning 7 degrees of latitude. The experiment includes spatial replicates of individual reefs and explicitly manipulates fishing mortality at the level of individual reefs to be able to distinguish fishing from natural effects. The benefits of the experiment are measured in terms of the bias and variance of estimates of quantities needed to develop a model to evaluate alternative spatially explicit management strategies for common coral trout, Plectropomus leopardus, on the Great Barrier Reef. The estimator considered is a variant of the Deriso G 980) delay-difference estimator. The benefits of the 1997 manipulations and future data collection in terms of the ability to estimate biomass and fishing mortality are demonstrated clearly. The magnitude of the benefits of additional manipulations in 1999 are smaller and depend on whether it will be possible to encourage fishers to increase fishing pressure for 12 months on the northernmost reefs and the reefs that are already open to fishing.