DIRECT ESTIMATES OF THE SELECTIVITY OF A MULTIMESH AND A SERIES OF SINGLE GILLNETS FOR BROWN TROUT

Hatchery brown trout Salmo trutta (1406) of length 5-20 cm were releas ed into a 7 . 5 ha shallow lake. They were recaptured with 28 multimes h gillnets of a type proposed for use in the Nordic countries and 42 s ingle gillnets of mesh size 8-22 mm (knot to knot). Corrected for the effect of different twine thicknesses, the single nets showed the high est selectivity for 16 . 5 mm and smaller meshes and the multimesh net s for the larger meshes. The height of the selectivity curves increase d exponentially with mesh size, and most distinctly for the multimesh nets. Over a limited range of mesh sizes the selectivity of the two ty pes of net did not differ much. Extended over mesh sizes 10 . 0-55 . 0 mm, the catching abilities of the two types of net became considerabl y different. (C) 1996 The Fisheries Society of the British Isles.