Predictive models for codend size selectivity for four commercially important species in the Mediterranean bottom trawl fishery in spring and summer: Effects of codend type and catch size

Models to predict codend size selectivity for four major commercial species—European
hake (Merluccius merluccius), Norway lobster (Nephrops norvegicus), deep-water rose
shrimp (Parapenaeus longirostris), and Atlantic horse mackerel (Trachurus trachurus)–in
Mediterranean bottom trawl fisheries were established based on data collected during fishing
trials using the two legal codends: a 40 mm square-mesh codend and a 50 mm diamond-
mesh codend. The models were applied to predict the extent to which size selection
depend on codend type, also accounting for the potential effect of codend catch size and
fishing season. The size selectivity of the two codends was evaluated and compared in identical
simulated controlled conditions. Mesh type significantly affected the size selection of
Norway lobster alone, with a slightly better performance of the 40 mm square-mesh codend.
A high risk of retention of undersized individuals was predicted for both codends for all species
except Norway lobster.