|Direct effects of beam trawl fishery on bottom fauna in the southern North Sea|
Bergman, M.J.N.; Fonds, M.; de Groot, S.J.; van Santbrink, J.W. (1994). Direct effects of beam trawl fishery on bottom fauna in the southern North Sea. BEON Rapport = BEON-report(13). [S.n.]: [s.l.]. 76-103 pp.
Part of: BEON Rapport = BEON-report. Programma Bureau BEON: Den Haag. ISSN 0924-6576, more
|Authors|| || Top |
- Bergman, M.J.N.
- Fonds, M.
- de Groot, S.J.
- van Santbrink, J.W.
Direct effects on benthic fauna of trawling with commercial 12m and 4m beam trawls for sole fishing, were studied in the southern North sea. Densities of fish and invertebrates before and after trawling were compared, in several study sites, both in soft bottom areas offshore and in sandy coastal areas. After trawling a study area twice, the direct mortality was estimated for a number of species. For different fish species, mortality varied from 2% of the numbers initially present (small under-sized fish) to 75% (larger fish). Mortality exceeded 100% for dab, rapidly immigrating into the trawled area, already during the trawl and the tickler chains. Mortality of invertebrates was mainly caused by the passage of the trawl and the tickler chains. Mortality was variable and species dependent, and estimated at 0-85% of the initial numbers for different species of molluscs, 4-80% for crustaceans, 0-60% for annelid species, and at 0-45% for echinoderm species. Discard composition varied with the type of beam trawl and the fishing ground. The total amount of discard was estimated as approximately 8-10kg dead fish and 4-6kg dead invertebrates per kg marketable sole. Dab was a predominant species in the discard, but also appeared to be a scavenger on damaged or exposed fauna on a recently trawled seabed.