Het belang van Rajidae voor de Belgische visserijsector. Casestudy: Analyse van de Belgische teruggooigegevens van vijf verschillende roggensoorten
Hanseeuw, E. (2011). Het belang van Rajidae voor de Belgische visserijsector. Casestudy: Analyse van de Belgische teruggooigegevens van vijf verschillende roggensoorten. MSc Thesis. Hogeschool Gent, Departement Biowetenschappen en Landschapsarchitectuur: Gent. 111 pp.
Within the Belgian fishery, the beam trawl is the dominant fishing gear technique. This method comes with a great amount of bycatch. One of the most economical valuable species in the bycatch are Rajidae (rays and skates). This thesis makes an analysis of the importance of Rajidae for the Belgian fishery. The data, which were collected under the Data Collection Regulation (DCR) (Commission Regulation EC no. 1639/2001), showed that the area being fished has a great influence on the size of the bycatch. The largest amount of bycatch (58%) was found in the Irish Sea (VIIa). Between the five species of Rajidae that were sampled, Raja montagui (57%) and Leucoraja naevus (37%) accounted for most of the discards. Discards of Raja clavata only accounted for 2%. Additional to this research was the optimization of the age reading technique in rays, based on previous research done by ILVO Fisheries. Because of the fact that rays are Elasmobranch fish, the aging has to be done by using vertebrae and can’t be done on otoliths like in Teolest fish.. The method that was used, cooking the vertebrae twice and not using coloring, provided vertebrae of which the age could be read. During the researches and analyses a few inconsistencies, regarding the data and data processing, were encountered. At the end of the research some suggestions are made on how these inconsistencies may be avoided and what researches all called for to improve the knowledge on Rajidae and their management.
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