A preliminary investigation of the effect of sea temperature fluctuations and wind direction on catches of chokka squid Loligo vulgaris reynaudii off the Eastern Cape, South Africa

Abstract

Opportunistically collected information on sea temperature and wind was used in a preliminary investigation of physical factors affecting jigged catches of chokka squid Loligo vulgaris reynaudii. Results revealed sea temperature and wind to be correlated with catches during part of the summer upwelling season (October and December) in 1988. Multiple linear regression analysis confirmed that sea temperature was a highly significant explanatory variable (p = 0,0000) for catches from three boats, as well as for the overall catch. Wind direction also played a significant role (p = 0,0085) in the overall catch. A statistical linear multiple regression model is proposed for each boat and for the total catch. Upwelling events are suggested to play a major role in the availability of squid on the inshore spawning grounds (<50 m) during summer. With further study, other independent physical variables, such as currents, swell height and turbidity, are likely to be introduced into the proposed model.