Browsing by Author "Hurtado, Carlos F."
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- Alternative codends to reduce bycatch in Chilean crustacean trawl fisheriesPublication . Queirolo, Dante; Erzini, Karim; Hurtado, Carlos F.; Ahumada, Mauricio; Soriguer, M. C.This study was conducted to determine the reduction in bycatch and the loss of target catch in trawl hauls for three commercial crustacean species (yellow squat lobster, Cervimunida johni, nylon shrimp, Heterocarpus reedi, and red squat lobster, Pleuroncodes monodon) in central Chile. Two experiments were carried out using the covered codend method; the first used different mesh sizes (56 and 70 mm, knot-centre to knot-centre) and shapes (diamond and square), and the second tested different reduction devices (escape panel and sorting grid). We analysed the escape proportions of the species caught and the size frequency distributions of the target species and Chilean hake (Merluccius gayi), the main commercial bycatch species. The results demonstrate that it is feasible to significantly reduce bycatch while keeping losses within acceptable ranges. In particular, the best option for yellow squat lobster was the combination of a 70-mm diamond mesh with an escape panel that reduced non-target and target catches by 48% and 7%, respectively. For nylon shrimp, the best option was the use of a 56-mm diamond mesh with a sorting grid that reduced non-target and target catches by 41% and 11%, respectively. Although the results for red squat lobster were not as promising, they will help to guide future research.
- Effects of environmental conditions and fishing operations on the performance of a bottom trawlPublication . Queirolo, Dante; Hurtado, Carlos F.; Gaete, Erick; Soriguer, Milagrosa C.; Erzini, Karim; Gutierrez-Estrada, Juan CarlosTrawl performance was studied based on net spread and variability in the contact of the footrope with the seabed and their relationship with vessel operations, catch weight, and environmental conditions. Artificial neural networks (ANNs) and generalized additive models (GAMs) were used to model the response of each variable. For the variables net spread and variability in footrope contact (VFC), the ANN models were more accurate than the GAMs, with greater generalization capacity in the validation phase. In the best ANN model for net spread, all variables were significant. The relationship between tow direction and wind direction (tactic) was most important in the sensitivity analysis. Net spread increased with increasing towing speed and windspeed, and decreased with increasing wave height. In the ANN model for VFC, there were differences among vessels, and both scope ratio and catch size were not significant. VFC increased with increasing depth and decreased with increasing towing speed and windspeed. The results demonstrate that both operational variables and environmental conditions affect trawl performance, and suggest that survey protocols designed based on this information might help to improve the precision of biomass estimates.