THE SIGNIFICANCE OF DISCARDS FROM THE BROWN SHRIMP FISHERIES FOR SEABIRDS IN THE WADDEN SEA - PRELIMINARY-RESULTS

Citation
U. Walter et Ph. Becker, THE SIGNIFICANCE OF DISCARDS FROM THE BROWN SHRIMP FISHERIES FOR SEABIRDS IN THE WADDEN SEA - PRELIMINARY-RESULTS, Ophelia, 1994, pp. 253-262
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Marine & Freshwater Biology
Journal title
Ophelia → ACNP
ISSN journal
0078-5326
Year of publication
1994
Supplement
6
Pages
253 - 262
Database
ISI
SICI code
0078-5326(1994):<253:TSODFT>2.0.ZU;2-V
Abstract
From December 1992 to August 1993, 33 one-day cruises of a commercial brown shrimp trawler in the East Frisian part of the Wadden Sea were a ccompanied to count the ship-following seabirds. The main scavengers w ere herring gull, black-headed gull and common gull. Other bird specie s behind the fishing vessels were less numerous. The numbers of birds varied greatly between 0 and 1,300, with monthly median of daily maxim um counts between 400 and 700. To evaluate the composition of a shrimp er's catch, fish and shrimps and other invertebrates in the catch were weighed and their length measured. Almost 90 % of the unsorted catch consisted of unwanted bycatch, which was discarded. 60 % of the catch was undersized shrimps, another 20 % consisted of fish and benthic inv ertebrates. Based on the catch composition and the landing statistics, the total amount of discards was estimated for the shrimp fishery of Niedersachsen. Accordingly, 18,400 t of undersized shrimps and 7,300 t of other benthic invertebrates and fish were discarded from April to August 1993. Discard experiments showed that the herring gull is the d ominant bird species behind the trawlers.