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The distribution of Branchiostoma senegalense (Acrania, Branchiostomidae) in the off‐shore shelf region off North West Africa

1975; Wiley; Volume: 60; Issue: 2 Linguagem: Inglês

10.1002/iroh.19750600204

0020-9309

Fritz Gosselck,

Marine Bivalve and Aquaculture Studies

Abstract During investigations on the macrobenthos between 17° N and 26° N on the North West African continental shelf, abundant stocks of Branchiostoma were found off Spanish Sahara (23° N‐25° N), on the d'Arguin Bank (21° N‐20° N) and off Gambia (12° N‐13° N). The lancelets were identified as Branchiostoma senegalense (WEBB, 1955) by means of statistical analyses. The lancelet populations occur at dephts down to about 40 m. Deeper regions are probably avoided because of the excessively high detritus content. Favourable environmental factors such as temperature, composition of the sediment and food supply permit high lancelet abundancies. Up to 9000 animals'm 2 were found in the population off Spanish Sahara. Rough calculations showed that the lancelet population comprises about 6 × 10 12 individuals with a biomass of 1.5 million tons. The potential natality amounts to about 45 × 10 15 larvae a year.