Effects of Codend Mesh Size and Twine Number on Nephrops Selectivity. Report on FISA project 03/13

Scottish Marine and Freshwater Science Vol 6 No 3

A set of trials were conducted in the West Coast to examine the selectivity of Nephrops (Nephrops norvegicus) with regards to codends with the following mesh size and construction: 80 mm diamond mesh codend of 4 mm single Brezline (PE) twine; 100 mm diamond mesh codend of 5 mm double Brezline (PE) twine; 120 mm diamond mesh codend of 5 mm double Brezline (PE) twine. The results can be summarised as follows: For Nephrops the catch rates of the 3 test gears differed significantly from each other. At a carapace length of 35 mm the 80 mm mesh showed 77% retention, the 100 mm codend showed 61% retention and the 120 mm codend showed 43% retention. For whiting (Merlangius merlangus) the catch rates of the 3 test gears differed significantly from each other with increasing selectivity as mesh size increased. For haddock (Melanogrammus aeglefinus) the selectivity increased as mesh size increased however, that of the 80 mm and 100 mm codends did not differ significantly from each other.