Seafloor mapping and landscape ecology analyses used to monitor variations in spawning site preference and benthic egg mop abundance for the California market squid (Doryteuthis opalescens)

Abstract

The California squid fishery is concentrated largely on nearshore squid spawning aggregations. Because of this practice a central concern for sustainable squid fisheries in California is to determine whether reproductive activities and subsequent egg laying occur at rates that are sufficient to support harvestable populations of this sub-annual species. Using high-resolution data collected via acoustic mapping methodology, we estimated a 99% decrease in egg mops abundance from 2005 to 2007. Sidescan sonar images from detailed benthic mapping suggest that although squids prefer a sandy substrate as their primary egg mop habitat, the depths across which egg mops were distributed differed significantly between surveys and spatial distribution of egg mops varied across years on this large spawning ground. Our results suggest that sidescan sonar surveys could serve as an important tool used to aid sustainable management of the California market squid fishery through the monitoring, designation and adaptive management of seasonally variable no-take spawning zones and can help in developing stock assessments of this commercially important species.