ENVIRONMENT - THE KEY TO UNDERSTANDING THE SOUTH-AFRICAN CHOKKA SQUID(LOLIGO-VULGARIS-REYNAUDII) LIFE-CYCLE AND FISHERY

This paper explores effects of environmental variability on the life c ycle of the chokka squid, Loligo vulgaris reynaudii in South Africa, p articularly the effect of physical and chemical influences on adult di stribution, and the availability of spawning aggregations to the local jig fishery. The following hypotheses are presented: 1) temperature, dissolved oxygen and currents have a direct effect on the demersal dis tribution of adult chokka on the feeding grounds, but this is restrict ed to the west coast where environmental conditions are more extreme r elative to the south coast, 2) chokka catches increase in proportion t o the extent of coastal upwelling, 3) spawning behaviour along the ins hore regions (<50m) is strongly influenced by turbidity near the seabe d. High turbidity forces the spawning population to lay their eggs in deeper waters, and are thus not available to the jig fishery. 4) El Ni no-Southern Oscillation (ENSO) events are linked with large fluctuatio ns in the availability of spawning squid aggregations to the inshore j ig fishery.