Cross-jurisdictional larval supply essential for eastern Australian spanner crabs (

Abstract

Context The spanner crab (Ranina ranina) stock of eastern Australia is distributed across two state jurisdictions and, as a non-migratory species with a pelagic larval phase, connectivity within this stock is likely to occur by larval dispersal, driven by ocean currents. Aims To understand connectivity and patterns of larval supply in the eastern Australian spanner crab stock. Methods Lagrangian particle tracking methods were used to simulate larval transport around the key spanner crab fishing regions in eastern Australia. Key results Spawning off central Queensland (Qld) supplies a large proportion of recruits, supporting both the Qld and New South Wales (NSW) fisheries. Lagged larval settlement showed significant correlations to catch-per-unit-effort and the proportion of total harvest taken within the NSW fishery, providing evidence to suggest that the NSW fishery may be reliant on spawning activity in Queensland. Conclusions The Qld and NSW fisheries are highly connected and the broad-scale patterns identified by the current modelling approach could provide an indicator of potentially good or bad recruitment years, particularly as finer resolution, and refined reproductive biology knowledge on spanner crabs becomes available. Implications The Qld and NSW fisheries are highly connected with a source–sink structure and it is recommended that a co-management strategy be adopted.