Study

Mitigation of seal-induced damage in salmon and whitefish trapnet fisheries by modification of the fish bag

  • Published source details Lehtonen E. & Suuronen P. (2004) Mitigation of seal-induced damage in salmon and whitefish trapnet fisheries by modification of the fish bag. ICES Journal of Marine Science, 61, 1195-1200.

Actions

This study is summarised as evidence for the following.

Action Category

Modify fishing pots and traps to exclude mammals

Action Link
Marine and Freshwater Mammal Conservation
  1. Modify fishing pots and traps to exclude mammals

    A controlled study in 2001 of a pelagic area in the Gulf of Finland, Finland (Lehtonen & Suuronen 2004) found that installing a wire grid and strengthened netting in trap-nets resulted in higher catches of undamaged salmon Salmo salar but not whitefish Coregonus lavaretus, likely due to reduced grey seal Halichoerus grypus predation. Average catch rates of undamaged salmon were greater in fish bags of modified trap-nets (6 kg/haul) than in conventional trap-nets (4 kg/haul). The difference was not significant for catch rates of undamaged whitefish (modified trap-nets: 33 kg/haul; conventional trap nets: 29 kg/haul). Five modified and five conventional salmon trap-nets were hauled 241 and 242 times respectively in June–August 2001. Four modified and four conventional whitefish trap-nets were hauled 173 and 180 times respectively in September–November 2001. Modified trap-nets had a wire grid (1.2 x 0.8 m with 2 mm wires spaced 175 mm apart) in the funnel of the trap and a fish bag made from Dyneema netting. Conventional trap-nets had an open funnel and fish bags made from elastic nylon (salmon trap-nets) or stiff polyethylene (whitefish trap-nets). Fish catches were weighed, and fish damaged by seals or seabirds were recorded, during each haul.

    (Summarised by: Anna Berthinussen)

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