The impact of the gillnet fishery on Merluccius merluccius (European hake) was investigated in the northern Tyrrhenian Sea, western mediterranean. Four mesh sizes were tested: 53,62.5,70 and 82mm.Horse mackerel (trachurus trachurus),hake and tub gurnard (Chelidonichthys lucerna) dominated the catches,from a minimum of 89% (82mm mesh) to a maximum of 97.8% (70mm) of the biomass caught. Efficiency of the four meshes was not significantly different with respect to the total hake catches.Selectivity on M.merluccius was assessed by Sechin and SELECT methods. Tangling was an important catch modallity for hake,as evidence by the the results of the Sechin model hich described only the first mode of thr size distributions corresponding to the entangled specimens.SELECT showed that the bi-modal function gave the best adjustment to the length-frequency distribution;the modal catch sizes were 33,39.2,43.6 and 51 cm total length respectively for the 53,62.5,70 and 82 mm mesh sizes. Taking into account the size of first maturity for females (35.1 cm TL), 62.5 mm is the most adquate mesh size for exploiting hake as it gives some protection to both immature specimens and large females.
Comparison of the catches of European Hake (Merluccius merluccius, L. 1758) taken with experimental gillnets of different mesh sizes in the northern Tyrrhenian Sea (western Mediterranean)
BELCARI, PAOLA;DE RANIERI, STEFANO;
2007-01-01
Abstract
The impact of the gillnet fishery on Merluccius merluccius (European hake) was investigated in the northern Tyrrhenian Sea, western mediterranean. Four mesh sizes were tested: 53,62.5,70 and 82mm.Horse mackerel (trachurus trachurus),hake and tub gurnard (Chelidonichthys lucerna) dominated the catches,from a minimum of 89% (82mm mesh) to a maximum of 97.8% (70mm) of the biomass caught. Efficiency of the four meshes was not significantly different with respect to the total hake catches.Selectivity on M.merluccius was assessed by Sechin and SELECT methods. Tangling was an important catch modallity for hake,as evidence by the the results of the Sechin model hich described only the first mode of thr size distributions corresponding to the entangled specimens.SELECT showed that the bi-modal function gave the best adjustment to the length-frequency distribution;the modal catch sizes were 33,39.2,43.6 and 51 cm total length respectively for the 53,62.5,70 and 82 mm mesh sizes. Taking into account the size of first maturity for females (35.1 cm TL), 62.5 mm is the most adquate mesh size for exploiting hake as it gives some protection to both immature specimens and large females.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
