Quantifying long-term discards from Queensland’s (Australia) east Coast otter trawl fishery

Abstract This article estimated the weight of annual discards in the Queensland east coast otter trawl fishery. Discards data were analysed using three generalized linear mixed models to derive adjusted discard rates, expressed as kg per retained catch, kg per boat day, and kg per area swept by trawls, respectively. Model explanatory terms included trawl fishing sector, presence/absence of bycatch reduction devices (BRDs), lunar phase, and whether the data were obtained from commercial vessels during their normal fishing activities or during research charters. Adjusted discard rates were then used to derive three estimates of annual discards and the average used to examine a long-term discard trends from 1988 to 2014. Total discards declined significantly from a peak of approximately 67 000 t in 1997 to approximately 21 000 t from 2011 to 2014, largely due to a decline in fishing effort, and to a lesser degree, the effects of BRDs that were mandated in the fishery in the early 2000s.