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Identifier 000388624
Title Χωροχρονικές διακυμάνσεις στη σύνθεση του αλιεύματος της μηχανότρατας στο Κρητικό πέλαγος
Alternative Title Spatial and temporal variation in the catch composition of trawl in the Cretan sea
Author Μεταξάκης, Εμμανουήλ Κ.
Thesis advisor Κουμουνδούρος, Γεώργιος
Reviewer Τσερπές, Γεώργιος
Σωμαράκης, Στυλιανός
Abstract Bottom trawl fisheries are of great importance in the Mediterranean, with this particular type of fishing corresponding at about 25-30 % of the total fishery production in Greece. Bottom trawl is a multispecific gear that catches a large number of commercial species while it also catches non-commercial species that are, usually, being discarded. The aim of the present dissertation is to study the composition of the bottom trawl fishery production in the Cretan Sea with emphasis on four common species (hake, mullet, pink shrimp, bogue). Production rates were related to season and depth. We individually studied both the landings and the discards with the use of Generalized Linear Modelling (GLM) in the R language environment. This particular study is the first in the Cretan Sea based on deyailed data for a whole fishing period after the establishment of the new fisheries legislation that requires the fishermen with trawls to use nets with a 40 mm mesh diameter and forbids this specific type of fishing, within 1,5 nautical miles from the coast. The results showed that both the landings and the discards rates are higher in the autumn, while the discarding index (catch per unit effort) increases with depth. The production and the discard rates of the examined commercial species differ among seasons and depths. Those differences could be attributed to the lack of bottom trawl fishing activity during summer and the biological characteristics and behavior of the species. This multispecific nature of the bottom trawl fisheries requires a systematic study on the biology of the species and the characteristics of the fishing gear, in order to achieve the goals for maximum sustainable yield, as prescribed by the Common Fisheries Policy of the European Union.
Language Greek
Subject Discards
Απορριπτόμενα
Issue date 2014-11-21
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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