Trap Catch of Green Sea Urchins Strongylocentrotus droebachiensis in Kelp Beds and Barren Grounds on the Norwegian Coast

Abstract

Abstract Field investigations were performed to find out if trap catch could be an alternative to diving to harvest green sea urchins (Strongylocentrotus droebachiensis). Laboratory experiments in y-maze tubes showed that starved sea urchins responded on tree different baits in about one minute, but they did not discriminate between offal of fish (saithe), sea urchin fodder, and lamina of kelp. The trap catch investigations were performed at 0–2.5 m depth in Ytre Karvika in Troms County and 2-m depth at Hjelmsoya in Finnmark County in autumn 2002 and summer 2003, respectively. Repeated catches 12 times at the same area in Ytre Karvika showed higher catches at the last six drags than the first six during one month of fishing. In the Hjelmsoya area highest catches were found in barren grounds with high densities (50–80 individuals m−2) of sea urchins, whereas in kelp beds the sea urchin catches did not exceed catches if baits were not used. Offal of catfish and cod heads caught higher catches than sea urchi...