Marine mammal research at wild salmon fisheries: Annual Report for 2013

Published source details Harris R.N., Fowden D., Froude M. & Northridge S. (2014) Marine mammal research at wild salmon fisheries: Annual Report for 2013. Sea Mammal Research Unit (SMRU) report, Seal and Salmon Research Project: report to Scottish Government and Scottish National Heritage, 29pp.
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This study is summarised as evidence for the following.

	Action	Category
	Modify fishing pots and traps to exclude mammals Action Link

Modify fishing pots and traps to exclude mammals

A controlled study in 2012 at a bay and harbour in the North Sea, Scotland, UK (Harris et al. 2014) found that fishing bag-nets with rigid steel bars, along with other modifications to prevent seal access, had greater catches of Atlantic salmon Salmo salar undamaged by seals than conventional bag-nets, but salmon took longer to pass through the modified net and a greater proportion escaped. Catch rates of undamaged salmon were almost twice as high in modified bag-nets than in conventional bag-nets (data reported as a catch rate index). However, salmon in the modified bag-net took longer to pass through the net (average 200 seconds) and a larger proportion swam back out of the net (65%) than in the conventional bag-net (average 44 seconds; 28%). A modified salmon bag-net and a conventional bag-net were deployed 250 m apart at a bay and a harbour. Modifications to the bag-net prevented seals from entering the inner chamber and trapping fish (e.g. rope-framed entrance replaced with rigid steel bars, heavier net material, a reduced mesh size in the net floor, tight corners inside the chamber closed off). Fishers reported fish catches and seal damage for modified and conventional bag-nets during a total of 130 hauls in July–August 2012.

(Summarised by: Anna Berthinussen)