Incidental catches of endangered (Phocoena phocoena) and vulnerable (Delphinus delphis) cetaceans and catch composition of turbot bottom gillnet fisheries in the southeastern Black Sea, Turkey

Abstract

The present study summarizes information on the incidental catches of cetaceans and the catch composition of turbot bottom gillnet fisheries between March 2010 and September 2011 along the Rize coast in the southeastern Black Sea, Turkey. A total of 723 specimens (133 Scophthalmus maeoticus, 507 Raja clavata, 8 Squalus acanthias, 71 Phocoena phocoena, 4 Delphinus delphis) were recorded from 136 turbot gill net fishing operations. the 'danger index' or catch per unit effort (CPUE, individuals per km. day of netting) for cetaceans was 0.09 +/- 0.028 in 2010, 0.15 +/- 0.032 in 2011 and 0.13 +/- 0.023 overall for P. phocoena and < 0.003 overall for D. delphis. Monthly CPUE values for target S. maeoticus and non-target species R. clavata, and P. phocoena were similar in all years. An increasing CPUE trend between April and June was evident for target and non-target species in 2010 and 2011. the CPUE of P. phocoena was estimated highest in May as 0.18 +/- 0.088 in 2010 and in April as 0.26 +/- 0.086 in 2011. A similar pattern was evident for S. maeoticus and R. clavata. One-way ANOVA showed that no statistical significant difference of target and non-target species CPUE among 2010, 2011 and all data (P > 0.05). No new net damage due to cetacean interactions with the turbot gill nets was detected.