The effects of an extraordinary El Niño / La Niña event on the size and growth of the squid Loligo opalescens off Southern California
Jackson, GD and Domeier, ML, The effects of an extraordinary El Nino / La Nina event on the size and growth of the squid Loligo opalescens off Southern California, Marine Biology, 142, (5) pp. 925-935. ISSN 0025-3162 (2003) [Refereed Article]
The population structure of the California market squid Loligo opalescens was studied for the Channel Islands region off Southern California between June 1998 and March 2000. During this time Californian waters were exposed to an extraordinary El NiÃ±o event that was possibly the most dramatic change in oceanographic conditions that occurred last century. There was then a rapid transition to record cool La NiÃ±a conditions. Statolith increments were used to determine age parameters and increment periodicity was validated for the first 54 days of life. Based on statolith increment counts, the oldest males and females were 257 and 225 days respectively and individuals matured as young as 129 and 137 days respectively. No distinct hatching period was detected. There was a general trend of increasing body size throughout the study period. Squid that hatched and grew through the El NiÃ±o were strikingly smaller and had slower growth rates compared to squid that grew through the La NiÃ±a. This was related to oceanography and associated productivity. There was a positive correlation between squid mantle length and upwelling index and a negative correlation between mantle length and sea temperature. The 'live-fast die-young' life history strategy of squid makes them ideal candidates for following the effects of the dramatic changes in oceanographic conditions off California. We propose that squid can serve as ecosystem recorders and productivity integrators over time and space and are useful organisms to tie oceanography to biology.