Monitoring catches in the pulse fishery
This report provides information on the catch composition of the Dutch pulse fishery targeting flatfish. Since 2007 in the southern North Sea, each Member State has a permit for 5 percent of the beam trawl fleet: that part of the fleet is allowed to fish with a pulse gear. In 2011, the permits were given by the EU under the condition that more information on the effects of pulse fishing would be collected. For this reason, the fishing industry started a catch monitoring program with the scientific support of research institute IMARES in December 2011. The catch monitoring program consisted of 25 vessels participating in a self-sampling program and ten observer trips on different vessels and fishing grounds throughout the year.
The self-sampling program showed an average catch composition in 2012 of 31% landings, 17% fish discards, 18% benthos, and 34% debris. In addition, the results show that there is variation in discards between quarters and between the five fishing areas that were defined in the analysis. However, no clear seasonal or spatial patterns have been distinguished. The average catch composition of the observer program consisted of 29% landings, 29% fish discards and 42% benthic species and debris.
The results from 2012 of the two programs and from vessels larger than 300hp are compared to check the consistency of the self-sampling method. The catch comparisons showed three significant differences between the self-sampling and observer program: the catch of benthos & debris, sole discards and cod landings are significantly higher in the self-sampling program. The differences in results may be due to the fact that fishing took place in other times and in other areas.
The benthos catches of the pulse observer program (2012, >300hp) are compared with the benthos catches of the beam trawl fishery (2012, >300hp) from the Data Collection Framework program. No self-sampling data on species level is available. The numbers of starfish and crab caught in the pulse trawl trips were lower than in the conventional beam trawl trips. The pulse vessels caught 16% of the number of starfish caught with the conventional beam trawl and 42% of crabs. The numbers of caught starfish and crabs are good indicators of the caught benthos quantities in the pulse and beam trawl fishery; these results indicate that the pulse fishery therefore catches less benthos compared to the beam trawl fishery.
The plaice and sole catches of the pulse self-sampling and observer program (2012, >300hp) are compared with the plaice and sole catches of the beam trawl fishery (2012, >300hp) from the Data Collection Framework program. The average discard percentage of plaice from the pulse trawl observer program (52%) is similar to the plaice discard percentage of the beam trawl trips (49%). The average discard percentage of the pulse self-sampling program is lower (42%). The actual amount of plaice discards caught in the pulse self-sampling (27 kg/hour) and observer program (66 kg/hour) are lower than in the beam trawl fishery (87 kg/hour).
The average sole discard percentage of the pulse observer program (10%) is lower than the average sole discard percentage of the pulse trawl self-sampling trips (15%) and the beam trawl trips (17%). The amounts of sole discards caught in the pulse self-sampling (6 kg/hour) and observer program (4 kg/hour) lie in the same range as the sole discard catches in the beam trawl fishery (6 kg/hour).
Cod catches are very low in both the pulse self-sampling and observer program. The self-sampling program showed an average landing rate of 3 kg/hour and an average discard percentage of 7%. The observer program showed an average landing rate of 1 kg/hour and an average discard percentage of 12%. Cod catches are too low to make a reliable comparison with the beam trawl fishery.
Dit onderzoek is mede gefinancieerd door het Europees Visserij Fonds (EVF) in het kader: Investering in duurzame visserij.