Reduction of harbour porpoise (Phocoena phocoena) bycatch by iron-oxide gillnets

Published source details Larsen F., Eigaard O.R. & Tougaard J. (2007) Reduction of harbour porpoise (Phocoena phocoena) bycatch by iron-oxide gillnets. Fisheries Research, 85, 270-278.
Share Tweet Email

This study is summarised as evidence for the following.

	Action	Category
	Use acoustically reflective fishing gear materials Action Link

Use acoustically reflective fishing gear materials

A replicated, controlled study in 2000 of six pelagic sites in the North Sea, Denmark (Larsen et al. 2007) found that fishing nets made from an acoustically reflective material (iron-oxide) had fewer entanglements of harbour porpoises Phocoena phocoena than conventional nets. No porpoises were found in entangled in iron-oxide nets, whereas a total of eight porpoises (average 0.1 porpoises/km/day) were entangled in conventional nets. Average catch rates of target cod Gadus morhua were lower in iron-oxide nets (6–15 fish/km/day) than conventional nets (8–32 fish/km/day). Each of six sites was fished for three days with 4–8 strings (50 x 60 m gill nets) of each of two net types: high-density iron-oxide nets and conventional nylon nets. The authors did not find a significant difference in acoustic target strengths between the two net types (see original paper for details) and suggest that other factors (e.g. net colour, stiffness, mechanics) may have reduced porpoise entanglements. An observer on board a chartered commercial fishing vessel recorded the number of entangled porpoises and fish catches as the nets were hauled in September–October 2000.

(Summarised by: Anna Berthinussen)