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The biology of the hottentot Pachymetopon blochii(Val.) and the silverfish Argyrozona argyrozona (Val.) along the Cape south-west coast
De Villiers Nepgen, C.S. (1977). The biology of the hottentot Pachymetopon blochii(Val.) and the silverfish Argyrozona argyrozona (Val.) along the Cape south-west coast. Sea Fisheries Branch Investigational Report, 105. Dept. Of Industries, RSA: Cape Town.
Part of: Investigational Report = Onderzoekverslag. Republic of South Africa. Department of Industries. Sea Fisheries Branch: Cape Town. ISSN 0379-1084, more

Keyword
    Marine

Author  Top 
  • De Villiers Nepgen, C.S.

Abstract
    Hand-line samples of hottentot Pachymetopon blochii and silverfish Argyrozona argyrozona from the Cape south-west coast were examined. The length-mass relation for the two sexes was determined separately in both fish species. Age was determined by means of otoliths and according to the von Bertalanffy equation, the mean annual increase in fork ]ength for the yearclasses II to VIII is 2.6 cm for hottentot and 3,4 cm for silverfish. The calculated total mortality for hottentot was 28 per cent and that for silverfish 18 per cent. According to fecundity calculations a hottentot of 30 cm in length has in its ovaries a mean of 493000 yolked, opaque ova and a silverfish of 50 cm 1 656 000 ova. Hottentot do not have a specific spawning season whereas silverfish spawn mainly during summer. Hottentots are omnivorous and their food consists of seaweeds, echinoderms, crustaceans and molluscs while silverfish are carnivorous and live mainly on fish, crustaceans and cephalopods. Hottentot do not undertake large-scale migrations but silverfish sometimes do.

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