Biological studies on the chokker squidloligo vulgaris reynaudii(Cephalopoda; Myopsida) on spawning grounds off the south-east coast of South Africa

Abstract

The biology of the chokker squid Loligo vulgaris reynaudii on inshore grounds in the South-East Cape was studied by examination of trends in jig catches, length frequency analyses, length/weight relationships, analyses of maturity stages and SCUBA diving transects in a spawning area. Commercial catches probably reflected the influx of squid into shallow waters to spawn. Modal length at spawning was between 265 and 305 mm mantle length (ML) in males and between 175 and 195 mm ML in females. There was no modal progression to indicate growth, nearly all squid were mature, a percentage of males were spent, the level of feeding on the grounds was very low, and mantle walls were thinner than those of squid offshore. These factors all indicate that the squid population inshore had reached the end of its life cycle and was in the spawning phase. The sex ratio was biased towards males, an indication either of differential inshore migration or of greater longevity in males than in females. The frequency of occurren...