Physical oceanographic processes affecting catchability of spanner crab (Ranina ranina)—A review

• Temperature, currents, and swell affect spanner crab catch.
• Large scale physical oceanographic processes are important to crab catchability.
• Findings underpin the importance of data collection methodology.
• Effect turbidity has on catchability requires further research.

This review examines the influence of physical ocanographic processes on catchability of spanner crab (Ranina ranina) in northeast Australia. Physical oceanographic processes may affect crab catchability by influencing their activity levels and ability to detect bait. Bottom temperature, current velocity, and swell intensity appear to influence catches of spanner crab. At this stage, it appears warmer temperatures enhance catchability of spanner crab. Spanner crabs were more catchable in stronger currents, and crabs were observed to arrive from down-current of baited traps. However, a decline in catch was observed following periods of intense swell. Data derived from Waverider buoys suggest that occasionally these periods create strong wave-induced seabed current velocities, lead to at depths of 70 m. The oscillatory motion of wave-induced seabed velocities may cause higher suspended sediment concentrations. These observations corroborate the views of local fishermen that spanner crabs avoid ‘murky’ water. The effect of turbidity on catchability requires further research. Overall, we advocate that studies employ robust methodologies to measure physical oceanographic processes to accurately predict catchability. Moreover, large-scale physical oceanographic processes may also play an important role in catchability of spanner crab; including upwelling, eddies, and the East Australian Current. Integrating physical oceanography and fisheries interactions will considerably benefit commercial fishermen as well as provide valuable information for evidence-based management of these valuable resources.