Sfruttamento della risorsa biologica associata alla pesca a strascico nell'area di Civitavecchia e impatto sulle comunità demersali e bentoniche
Author(s)
Tiralongo, Francesco
Date Issued
June 17, 2016
Type
Doctoral Thesis
Abstract
The purpose of this study is to evaluate the status of the resource exploitation and the amount of bycatch caught by bottom trawlers operating along the Civitavecchia coast, Tyrrhenian Sea. The study was conducted from October 2014 to October 2015. Seventy-eight bottom trawler operations were sampled for a total of 24 fishing days. The study highlights the presence of two distinct fishing areas: inshore (50-120 m) and deep (240-500 m). The quali-quantitative catch composition of commercial species and bycatch was determined. Each fishing area was characterized by a well defined demersal and benthic community. Two eurybathic target species, Merluccius merluccius and Parapenaeus longirostris, were caught in large quantities in both in inshore and deep fisheries field. Catch yields and the ecological use efficiency (E.U.E.) showed the highest values in October (after the biological fishing ban) and this seems highlights the positive correlation between the biological fishing ban and the stocks recovery. Bycatch represented about the 20-30 % of the total catch. This would indicate a good compromise between the resource exploitation and the impact on demersal and benthic community. Bycatch was represented by undersized specimens, fishes of low or no economical value and by epifaunal macrobenthic invertebrates. Undersized species were about the 41% of the biological discard. A total of 246 species were recorded, of which 130 (52.85%) were sampled between 50 and 120 meters in depth (inshore fisheries). Shannon-Wiener and Pielou indices were lower in summer. The main taxonomic groups were represented by fishes, crustaceans, mollusks and echinoderms. Depth and associated parameters seem to be the main factor affecting community composition.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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