Spatiotemporal patterns of rockfish bycatch in US west coast groundfish fisheries: opportunities for reducing incidental catch of depleted species

Abstract

Spatial and temporal management measures to reduce nontarget catch are important strategies for rebuilding overfished rockfish (Sebastes spp.) populations in the Northeast Pacific. We describe efforts to support reducing rockfish bycatch in central California trawl fisheries by testing the efficacy of move-on rules on catch data from 2002 to 2010. Move-on rules are regulations or guidelines that trigger the temporary closure of a fishery in a targeted area when a bycatch threshold is reached, without the closure of the entire fishery. Move-on rules based on spatiotemporal autocorrelation (clustering) were effective in reducing bycatch with modest impact on target catch, removing between 35% and 77% of future hauls with bycatch within a specified distance and time of a bycatch-containing haul, while foregoing target catch by an average of 12%. The spatial and temporal peak clustering scales show correlation with the level of schooling behavior by each species; however, the efficiency of the rules measured either in reduction in bycatch hauls or diminished target catch was not strongly affected by those aggregation behaviors. Our analysis provides information for fishers, such as those in the California Risk Pool, in the continuing development of responses that are more refined in both scale and impact.