California Sea Grant College Program

Opalescent squid, Loligo opalescens, captured from central and southern California fisheries were examined for long-term changes in size, sex ratio, and fecundity. Samples were collected in Monterey from 1948 to 2006 and in the Channel Islands and Catalina Island from 1999 to 2007. A significant (P<0.0001) decline in opalescent squid size and fecundity occurred in Monterey. The trend in monthly mean sizes was similar among locations. Monthly mean sizes were negatively correlated with fishing pressure; when fishing pressure was strong, smaller individuals were captured the following fishing season. Body size was also negatively correlated with hatch-month sea surface temperature (SST). Negative correlations between anomalies for monthly mean SST and sizes were found—individuals grew larger if a winter was anomalously cooler. In addition, monthly mean upwelling and body sizes were positively correlated during the juvenile stage. The ratio of males to females captured in the fishery fluctuated in all areas.