Percorrer por autor "Gaete, E."
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- Alternative codends to improve the size selectivity for nylon shrimp (Heterocarpus reedi) and yellow squat lobster (Cervimunida johni) off the Chilean coastPublication . Queirolo, D.; Hurtado, C. F.; Ahumada, M.; Gaete, E.; Soriguer, M. C.; Erzini, KarimThe size selectivity of alternative codends for nylon shrimp and yellow squat lobster was studied off the Chilean coast using the covered codend technique. Various mesh sizes (47 and 63 mm mesh opening) and shapes (diamond and square) in the codends were used. For both species, substituting the DM47 codend with the DM63 codend significantly increased 50% retention length (l50). The change of diamond (DM47) to square mesh (SM47) had a positive effect in size selectivity for nylon shrimp. For yellow squat lobster, no significant effect was observed when changing the diamond (DM63) to square mesh (SM63). Selectivity data were modeled by considering explanatory variables such as codend catch weight and vessel. Increases in the catch significantly reduced the l50 for both species whereas the vessel factor was not significant. Finally, using the length at first maturity as a reference value, the authors concluded that the DM47 codend failed to protect the immature portion of either stock, thus the DM63 codend is recommended.
- Behaviour of fish by-catch in the mouth of a crustacean trawlPublication . Queirolo, D.; Gaete, E.; Montenegro, I.; Soriguer, M. C.; Erzini, KarimThe behaviour of fish by-catch was recorded and characterized by in situ observations in the mouth of a crustacean trawl using an underwater camera system with artificial light, at depths between 106 and 461 m, along the central coast of Chile. The groups or species studied were rattails (family Macrouridae), Chilean hake Merluccius gayi gayi, sharks (orders Carcharhiniformes and Squaliformes), skates (family Rajidae), flatfishes (genus Hippoglossina) and small benthopelagic and demersal fishes (orders Osmeriformes, Stomiiformes, Gadiformes, Ophidiiformes and Perciformes). The fish behaviour was categorized in terms of (1) position in the water column, (2) initial orientation with respect to the trawl, (3) locomotion and (4) swimming speed with respect to the trawl. Rattails, sharks, skates and flatfishes were passive in response to the trawl and showed similar behavioural patterns, with most fishes observed sitting or touching the bottom with no swimming or other activity. Merluccius gayi gayi was the most active species, displaying a wide combination of behavioural responses when the trawl approached. This species showed several behavioural patterns, mainly characterized by swimming forward at variable speed. A fraction of small bentho-pelagic and demersal fishes also showed an active behaviour but always at lower speed than the trawl. The species-specific differences in behaviour in the mouth of the trawl suggest that improvements at the level of the footrope can be made to reduce by-catch, especially of passive species.
- Species composition and bycatches of a new crustacean trawl in ChilePublication . Queirolo, D.; Erzini, Karim; Hurtado, C. F.; Gaete, E.; Soriguer, M. C.The species composition and bycatches of a new trawl for crustaceans (Heterocarpus reedi, Cervimunida johni and Pleuroncodes monodon) was studied in central Chile between 2007 and 2009. The spatial and temporal variations of the catch composition were analyzed using univariate and multivariate comparison techniques. In 289 trawl hauls, 72 taxa were recorded, with target species accounting for most of the catch, while the bycatch consisted mainly of Merluccius gayi, Hippoglossina macrops, Coelorinchus aconcagua, Epigonus crassicaudus and Platymera gaudichaudii. 14 species of elasmobranchs were identified, and at least one of these species was present in 50% of the hauls made. The classification and ordination methods showed the existence of three groups, each one associated with a target species, with no significant spatial and temporal effects. The information obtained in this study represents the basis for setting targets in order to reduce the bycatch captured by this trawl. The focused strategy on the most recurring and sensitive species for these fisheries is also discussed. (C) 2011 Elsevier B.V. All rights reserved.