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The rock lobster Jasus lalandii and its environmental biology of the Saldanha-Columbine fishing ground off the Cape West coast, 1978-1981
Pollock, D.E.; Augustyn, C.J.; Goosen, P.C. (1982). The rock lobster Jasus lalandii and its environmental biology of the Saldanha-Columbine fishing ground off the Cape West coast, 1978-1981. Sea Fisheries Branch Investigational Report, 125. Sea fisheries inst.: Cape Town. 30 pp.
Part of: Sea Fisheries Branch Investigational Report, more

Keyword
    Marine

Authors  Top 
  • Pollock, D.E.
  • Augustyn, C.J.
  • Goosen, P.C.

Abstract
    A large and important rock-lobster fishing ground on the South African west coast was studied over a three-year period -Tagging was used for estimating growth and diving surveys were conducted to investigate the rock-lobster population and the sessile benthos- eggs-bearing extended from June to about October, except for the isolated North Blinder where berried females were observed en masse as late as January. Males appeared to moult mainly just before the fishing season opens in November and their growth increments declined with increasing size of animal. Mean increments were 5 to 6 mm carapace length in the smallest males tagged (80 -89 mm carapace length) over most of the ground. Growth increments of males from North Blinder were significantly smaller (2.5- 2.9 mm in the 80-89 mm size class) and the mean size in commercial catches was smaller here than on the remainder of the fishing ground. Growth increments of females were very small (0.9 mm carapace length)in all areas. Quantitative benthic surveys showed a relative scarcity at North Blinder of mussels Aulacomia ater which are the main food of rock lobsters. The sea-bed at North Blinder was dominated by sponges in contrast to other areas investigated. A general decline in mean size of rock lobster caught commercially took place between the two seasons,implying that current exploitation rates are making a significant impact on stocks. Rates of tag return were moderate at North Blinder and lower elsewhere on the fishing ground, but returns may have been biased by tag-losses in males and non-reporting of berried females.

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