Spatio-temporal patterns in maturation of the chokka squid (Loligo vulgaris reynaudii) off the coast of South Africa

Olyott, L.J.H. and Sauer, W. H. H. and Booth, Anthony John (2006) Spatio-temporal patterns in maturation of the chokka squid (Loligo vulgaris reynaudii) off the coast of South Africa. ICES Journal of Marine Science, 63 (9). pp. 1649-1664. ISSN 1054-3139



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Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.

Item Type:Article
Uncontrolled Keywords:biology; chokka squid; Loligo vulgaris reynaudii; spatial; temporal; variability; South Africa
Subjects:Y Unknown > Subjects to be assigned
Divisions:Faculty > Faculty of Science > Ichthyology & Fisheries Science
ID Code:412
Deposited By: Mrs Eileen Shepherd
Deposited On:22 Nov 2006
Last Modified:01 Aug 2012 12:29
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