Abstract
Summary: This short-term study on commercial discards was carried out in fishing grounds around Gokceada Island in the northeastern Aegean Sea, a geographic area where fisheries information is rather limited. A total of 28 bottom trawls were performed between 70 and 410 m depth from December 2009 to February 2010. All the samples were collected on board a commercial trawler under commercial fishing conditions. A total of 3143 kg of biomass was caught in 28 valid hauls. Landings accounted for about 67% of the total catch while the remaining 33% was discarded. Fish species comprised 85% of the total catch and their composition could be divided into four main groups related to depth: shallow shelf (70 to 88 m), deep shelf (155 to 180 m), shelf break (196 to 276 m), and upper slope (307 to 410 m). Fish dominated the abundance and biomass of both landings and discards in all bathymetric strata. Echinoderms also accounted for a large proportion of the discards. Mean total catches varied between 78.4 kg/h on the shallow shelf and 38.1 kg/h on the shelf break with no differences in the landing biomass between groups, but with slightly higher discards over the shallow shelf. Taking into account the preliminary nature of the findings, based on a short-term analysis, the minimum mesh size and minimum landing size currently applied in the Turkish bottom trawl fishery are not sufficient to reduce discards and to protect juveniles of commercially important species in the northeastern Aegean Sea.
Highlights
During the last few decades, scientific studies have revealed the intensive impact of fishing activities on ecosystems (e.g. Jennings and Kaiser 1998)
Landings accounted for about 67% of the total catch while the remaining 33% was discarded
Fish species comprised 85% of the total catch and their composition could be divided into four main groups related to depth: shallow shelf (70 to 88 m), deep shelf (155 to 180 m), shelf break (196 to 276 m), and upper slope (307 to 410 m)
Summary
During the last few decades, scientific studies have revealed the intensive impact of fishing activities on ecosystems (e.g. Jennings and Kaiser 1998). The fishing techniques in use in the Mediterranean Sea are highly diverse, but bottom trawling has the greatest ecosystem impact because it involves a wide range of species and different functional groups (Coll et al 2006, Moranta et al 2008, Tsagarakis et al 2013). Discards produced by this fishing activity account for 20% to 70% of the total catch depending upon the geographic area, depth range and type of habitat where fishing occurs Available studies have revealed differences in the demersal assemblages between these regions (Tsimenides et al 1991, Kallianiotis et al 2000, 2004, Labropoulou and Papaconstantinou 2000, Katsanevakis and Maravelias 2009, Klaoudatos et al 2010)
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