Discard sampling of the Dutch pelagic freezer fishery in 2010

This report contains the results of the discard sampling programme of the Dutch pelagic freezer trawler fleet in European waters in 2010. The pelagic freezer trawler fishery targets pelagic species, namely herring (Clupea harengus), blue whiting (Micromesistius poutassou), horse mackerel (Trachurus trachurus), mackerel (Scomber scombrus), greater argentine (Argentina silus), and pilchard (Sardina pilchardus). The annual landings of this fishery illustrates its seasonality; different species are targeted during different parts of the year. The total landings of the Dutch fleet were about 201,000 tonnes in 2010. Horse mackerel and herring were the most abundant landed species. Overall, the discard percentage for the Dutch pelagic fleet in 2010, based on 8 sampled trips, is estimated at 6% in weight. This is consistent with the discard percentages that have been found in previous years. However, in 2010 we did not succeed in sampling the fishery each quarter of the year; no trip was sampled in quarter 3. On board of the pelagic freezer trawlers two different discarding methods are observed, namely discarding after the catch is sorted and discarding prior to sorting. The latter includes catch that is discarded directly or via the conveyer belt from the cooling tanks, and catch that is slipped from the net. Due to practical limitations and safety issues it is not possible to sample these discards. The results show that the estimated amount of unsampled discards represent 30% of the total estimated discards. Motivations for discarding unsampled catch can vary. Anecdotal information implies most incidents of discarding take place when more fish is caught than can be stored in the cooling tanks. In addition, fish-quality issues, unprofitable mixtures of species, or a lack in quota, could also be reasons for this discarding behaviour. The discard composition and length frequency data shown in this report are only based on routinely sorted discards. Discard percentages of target species herring, horse mackerel, and blue whiting are relatively low (1%, 1%, and 4% respectively). For mackerel the discard percentage is significantly higher (18%). The present study therefore suggests that, with the exception of mackerel, this fishery is efficient, when it comes to targeting (marketable) fish.