Local fishing efficiencies estimated from observers' recordings of Patagonian toothfish (Dissostichus eleginoides)

摘要

The growing capacity of fishermen to repeat fishing operations at some known locations thanks to, for instance, precise maps of past activity and global positioning systems (GPS) is becoming more apparent as fine-scale information on fishing activities becomes available. Aggregated declarations at the level of statistical square levels hides the fine-scale information and the possibility to analyze small-scale fishing strategies. When available, information on fishing effort such as observers' declarations or vessel monitoring system (VMS) reports may indicate that the tendency of specific-area repeat fishing is sometimes frequent (Rijnsdorp, van Mourik Broekman and Visser 2000). In this paper, we are concerned by the fact that small-scale fishing tactics may interfere in the relation between commercial catch per unit effort (CPUE) and indices of abundance and potentially reduce the relevancy of mean CPUE for resource analysis purposes. The relationship between CPUE and abundance can be biased (e.g. Hillborn and Walters 1987, Rahikainen and Kuikka 2002) as it is the product of several processes such as schooling behaviour of fish, variation in catchability, interactions between fishing vessels and spatial distribution of fishing effort.