EXPERIMENTAL EVALUATION OF BYCATCH REDUCTION DEVICES IN SHRIMP-TRAWL NETS OF SHALLOW WATERS OF THE COLOMBIAN PACIFIC COAST

Abstract

The effects of the introduction of bycatch reduction devices in the shrimp trawling fleet in shallow waters of the Colombian Pacific, were tested through an experiment fishing involving the industrial fishing sector. Following the commercial fishing conditions, we evaluated the turtle excluder device (TED), the "fish eye" fish excluder device (OP) and the combination of both devices (DET + OP). The variables used to assess the effects of the devices on the different components of the catch [target catch (CO), bycatch (CI) and discard (D)] were the relative abundance and length distribution of individuals. The effects of device type, fishing areas and their interaction were assessed by two-way ANOVA, while the effect of the devices on the length structure of catches was evaluated by comparison of size distributions using the Chi-square test. The overall ratio between the target catch (shrimp) and bycatch was 1:14. Groups of species caught were fish (83 %), crustaceans (13 %), molluscs (1.1 %), cnidarians (1.3 %), reptiles (1 %) and echinoderms (0.6 %), which together included 216 taxa. The variables TCO, CI (commercial fish) and D (discards) all varied significantly between fishing grounds. The devices did not affect shrimp catch in trawl nets, but fish catch did depending on the fishing grounds. The performance of devices showed with respect to the CI that DET excluded 45 %, the OP 36 % and OP+DET 78 %, while the discard was reduced by 22 % with the DET, 39 % with OP and 58 % in the DET + OP. The length distributions of the trawl-net with devices did differ significantly from the control net. The devices tested reduced the impact of trawling on marine biodiversity by allowing the escape of many species. However, the escape of commercial size fish could affect the income of fishermen.