Abstract
The definition of catch intention in multispecies fisheries is a key step toward building abundance indexes based on commercial fishing data. Previous analysis to determine catch intention in the pink cusk-eel (Genypterus blacodes) has been based on the idea that fishing tactics remain constant over time (static fishing tactics). We propose a statistical procedure to determine the catch intention of each haul in the industrial longline fisheries in southern Chile, where fishing tactics may vary over time. This procedure is based on principal component analysis and agglomerative hierarchical analysis of the catch composition, and relaxes the assumption of static fishing tactics by selecting a subset of data that is informative for fishing intention (target versus by-catch) every year. Sensitivity analyses were conducted to assess the robustness of variable fishing tactics on the nominal catch rates in pink cusk-eel. Targeted and by-catch time series of nominal catch rates showed a different trend, so determining the catch intention became relevant. Sensitivity analyses showed that trends in targeted catch rates are robust to the variations of fishing tactic per year. We recommend the use of variable fishing tactics for further use in effort standardization and stock assessment of the pink cusk-eel fishery in southern Chile.
Highlights
Pink cusk-eel (Genypterus blacodes) is one of the most important fish harvested off southern Chile in terms of landing volumes, local consumption levels and fishing history
We propose a new procedure for identifying fishing tactics across years, which relaxes the assumption of static fishing tactics by selecting a subset of data informing on fishing intention every year that can be used for further effort standardization analyses
We considered that a proportion of Patagonian toothfish of less than 50% is likely to correspond to those caught as a by-catch of the pink cusk-eel fishery
Summary
Pink cusk-eel (Genypterus blacodes) is one of the most important fish harvested off southern Chile in terms of landing volumes, local consumption levels and fishing history. First official landing records of pink cusk-eel in Chile date back to industrial trawlers operating in the Chilean austral zone in 1978 (41°28.6′S-57°00′S, Fig. 1). Pink cusk-eel is harvested in Chile by multiple fleets that target several other species, and the fishery is divided into two fleet components, industrial and artisanal. The industrial fleet is comprised of trawlers and longline vessels operating exclusively in the open sea, whereas the artisanal fishery is comprised of longline vessels operating in the fjords and inner channels of the austral zone. The pink cusk-eel fishery is one of the few in Chile that has been monitored since its beginnings in the early
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