Vulnerability of spawning aggregations of a coastal marine fish to a small-scale fishery

Abstract

For marine fishes that form spawning aggregations, vulnerability to aggregation fishing is influenced by interactions between the spatio-temporal patterns of spawning and aspects of the fishery that determine fishing effort, catch, and catch rate in relation to spawning. We investigated the spatio-temporal dynamics of spawning and fishing for the barred sand bass, Paralabrax nebulifer, in Punta Abreojos, Mexico from 2010 to 2012 as a means to assess its vulnerability to aggregation fishing by the local commercial fishery. Monthly, spatial patterns in gonadal development in collected females indicated that adults formed spawning aggregations at two sites in Punta Abreojos during July and August. Monthly patterns in the spatial distribution of fishing matched the spawning behavior of P. nebulifer, with effort and catch concentrated at spawning aggregation sites during those months. However, fishing effort, catch, and catch-per-unit effort did not increase during the spawning season, and fishing activities associated with the spawning season comprised only a small percentage of the total annual effort (22%) and catch (17%). Therefore, while the population of P. nebulifer at Punta Abreojos should be vulnerable to aggregation fishing due to the spatio-temporal dynamics of its spawning aggregations, vulnerability is greatly reduced, because fishing activities are not disproportionately focused on spawning aggregations and fishing methods are not optimized to maximize harvest from the aggregations. Differences between our results and previous studies on aggregation fisheries for P. nebulifer in California, USA, reinforce the importance of assessing factors influencing vulnerability to aggregation fishing at regional scales for prioritizing management efforts.