Stock assessment of the Queensland east coast common coral trout (Plectropomus leopardus) fishery. April 2019

Abstract

Queensland’s common coral trout (Plectropomus leopardus), a species of grouper, is a line caught fish forming a single population (stock) across the Great Barrier Reef (GBR). Common coral trout are protogynous hermaphrodites (born female, many later changing sex to male) and aggregate to spawn during spring and summer. They can grow to 5 kg and 18 years of age.

The stock extends north from the GBR into the eastern Torres Strait where it is under Commonwealth jurisdiction. In financial year 2017-18, the Queensland jurisdiction accounted for around 90% of the total harvest.

From 2013-14 to 2017-18, the Queensland total harvest averaged 983 tonnes (t) per year. The catch breakdown is 82% commercial (806 t) and 18% recreational (177 t).

The previous stock assessment estimated that in July 2012 the stock was at 60% of unfished biomass (i.e. before fishing began) over the areas commonly fished by commercial fishers. This stock assessment updates the existing model to cover the full extent of the GBR in Queensland waters and includes harvest information from the recreational sector.

This stock assessment used a spatial age-structured model with a yearly time step based on financial years. The model considered twelve spatial sub-populations (“strata”) of fish based primarily on differences in coral reef habitat. The model incorporated data spanning the period from 1961-62 to 2017-18 (including commercial harvest (1988-89 to 2017-18); historical commercial (1961-62 to 1981-82); recreational harvest (1996-1997 to 2013-14); age monitoring (1994-95 to 2004-05); and underwater visual surveys (1982-83 to 2017-18)).

The purpose of this report is to estimate biological reference points. The model provides estimates of the level of biomass of common coral trout relative to unfished levels, maximum sustainable yield (MSY) and the yield consistent with a biomass ratio of 68% (a proxy for maximum economic yield in this fishery).