Forecasting fishing impacts on the population biology of the red bass Lutjanus bohar (B4.12S)

Task leader: Mr Ross Marriott, James Cook University .

Task associates:
Mr Martin Russell, Great Barrier Reef Marine Park Auhtority
Mr Mark Elmer, Queensland Fisheries Services.

The red bass (Lutjanus bohar) is a bycatch species of the commercial line fishery that operates within the Great Barrier Reef World Heritage Area (GBRWHA). L. bohar caught from the GBRWHA are not widely retained by commercial fishers because this species has a reputation for causing ciguatera fish poisoning. Smaller L. bohar are retained for sale by some fishers though because these are considered safe to eat. In other countries where ciguatera does not occur, such as the Seychelles, Papua New Guinea and Fiji, L. bohar is harvested in large quantities by artisanal and subsistence fisheries. Preliminary research indicates that this species grows slowly throughout life and can live for over 50 years. This indicates that L. bohar has a low resilience to harvest and could be vulnerable to overfishing.

Original research objectives for the Masters study involved the determination of other aspects of this species’ population biology such as seasonal spawning trends, the size and age when males and females mature, natural mortality rates and how observed growth trends can vary in different areas. The upgrade to Doctor of Philosophy utilises these data, plus historical catch and effort data from a heavily exploited population in the Seychelles to explore the ability of L. bohar populations to sustain harvest, fishing impacts on population biology, and the likely effectiveness of a minimum size limit management strategy from the development of an age structured model and computer simulation. The revised modelling approach will provide better scope for predicting fishing impacts and addressing specific theory.