Selectivity of gill nets for &lt;i&gt;Solea solea&lt;/i&gt; (Osteichthyes: Soleidae) in the Adriatic Sea

Gianna Fabi,Fabio Grati

doi:10.3989/scimar.2008.72n2253

Abstract

Sole juveniles concentrate along the western Adriatic coast where they are targeted from spring to autumn by small-scale gill netters. As in spring–early summer 20 to 30% of catch biomass consists of individuals smaller than MLS (TL = 20 cm), the selectivity of sole gill nets was investigated in 2004-2005 in order to obtain useful information for developing management measures aimed at reducing the retention of undersized specimens and assuring the sustainability of this fishery. Twenty-eight fishing trips were performed using sole gill nets with 5 mesh openings (64.2, 65.2, 67.8, 70.2 and 71.8 mm) simultaneously. The gill net selectivity was estimated indirectly by applying the SELECT method and between-set analysis. The log-normal curve was found to fit single set data better than other models. The catch yields did not significantly decrease with the increment of mesh size: the biomass of undersized individuals in catches noticeably decreased from 16% down to 9% in the largest mesh size, whilst the sole that were longer than the MLS increased proportionally. In view of the lower economic value of smaller specimens with respect to the larger ones, adopting the 71.8 mm mesh represents a good compromise between the need to protect juveniles and the economic profit of gill netters.

Highlights

In Italy the mean annual landing of sole Solea solea (Linnaeus, 1758) amounts to about 3000 tons, 60% of which comes from the northern and central Adriatic Sea (ISTAT, 2002-2005)
SUMMARY: Sole juveniles concentrate along the western Adriatic coast where they are targeted from spring to autumn by small-scale gill netters
As in spring–early summer 20 to 30% of catch biomass consists of individuals smaller than MLS (TL = 20 cm), the selectivity of sole gill nets was investigated in 2004-2005 in order to obtain useful information for developing management measures aimed at reducing the retention of undersized specimens and assuring the sustainability of this fishery

Summary

Introduction

In Italy the mean annual landing of sole Solea solea (Linnaeus, 1758) amounts to about 3000 tons, 60% of which comes from the northern and central Adriatic Sea (ISTAT, 2002-2005). In this area the sole catches are less abundant with respect to those of other demersal fish, such as the European hake Merluccius merluccius and the red mullet Mullus barbatus (ISTAT, 2002-2005), this species plays an important role for fisheries due to its higher economic value per unit weight, which is around two. In spring and summer, when this fishing activity is greater, 20 to 30% of catch biomass consists of individuals smaller than the Minimum Landing Size (MLS = 20 cm TL; Grati et al, 2002). These undersized specimens are not discarded but usually sold to retail

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