Catches of Greenland halibut (Reinhardtius hippoglossoides) in ghost fishing gillnets on the Norwegian continental slope

Abstract

Catches in deliberately “lost” gillnets were studied during a ten-day cruise conducted at Storegga 70 nm off the coast of mid-Norway in July 2000. Gillnet fleets were deployed at depths of between 537 and 677 m, and soak time varied from one to seven days. Four fleets set 45 days earlier were also retrieved during the cruise. Most of the catch (94 %) consisted of the target species Greenland halibut (Reinhardtius hippoglossoides). All individuals were categorized according to seven condition stages ranging from “alive with no injuries” to “only bones remaining”. Results revealed that fish could be fully decomposed/consumed within a 24-hour period, probably due to amphipod and isopod scavenger activity. A decline in total catches was first observed after five days whereas catch composition remained stable during the first seven days. After 45 days a relatively high total catch was obtained but only 25 % were still at stages 1-4 (consumable). The cumulative catch after 45 days was estimated at 2.7 and 3.0 tons on the basis of two different methods. Gillnets retrieved after 45 days were evaluated as being highly effective, with gear saturation being the only factor leading to decreased efficiency.