Interannual homing to reproductive sites and transboundary migration in black seabream Spondyliosoma cantharus, with implications for management

Fish spawning aggregations are vulnerable to overexploitation, which can have severe ecological, social, and economic consequences. Knowledge on the spatial ecology of aggregating species is often lacking, but is crucial for their effective conservation. This study explores the spawning site residency, interannual fidelity, and migration of black seabream Spondyliosoma cantharus using acoustic (n = 55) and conventional (n = 2397) tagging within and outside Marine Conservation Zones in the southern UK. Detections and recaptures of tagged fish indicated that black seabream display significant interannual fidelity to nesting areas, but that residency of individuals at nesting areas was short relative to current temporal management of these areas. Locations of detection and recapture during autumn/winter indicated migration by black seabream into deeper waters of the English Channel and coastal waters of France and the Channel Islands. The results indicate spatial structuring of black seabream populations maintained by homing of adults to previously occupied sites. However, short residency periods within protected reproductive sites, and evidence of transboundary migrations emphasize the importance of effective fisheries management, i.e. collaborative between European nations. These findings highlight the importance of international-scale telemetry studies and networks for informing ecosystem-based fisheries management of sensitive migratory species.