Electronic monitoring of incidental bycatch of harbour porpoise (Phocoena phocoena) in the Dutch bottom set gillnet fishery (September 2013 to March 2017) Wageningen Marine Research Report C102 18
Meike Scheidat, Bram Couperus and Marije Siemensma
This study assessed the bycatch of harbour porpoise (Phocoena phocoena) in the Dutch commercial bottomset gillnet fishery, which is one of the priorities defined in the Dutch â€œHarbour porpoise conservation planâ€.
The results showed that bycatches occur in both single-walled gillnets (GNS) as well as trammel nets (GTR) and that the average annual bycatch of harbour porpoise for this fleet was 23 (95% C.I. 2-44) during the study period. This translates to an annual mortality of between 0.05 and 0.07% of the Dutch harbour porpoise population (with a maximum worst case value of 0.3%). ASCOBANS (resolutions 3.3 and 5.5) advises to follow the â€œprecautionary objective to reduce by-catches to less than 1% of the best available population estimateâ€. This study did not include mortality caused by other fishing fleets operating in Dutch waters.