Reburial potential and survivability of the striped venus clam (Chamelea gallina) in hydraulic dredge fisheries

Giada Bargione,Claudio Vasapollo,Alessandro Lucchetti,Massimo Virgili,Andrea Petetta

doi:10.1038/s41598-021-88542-8

Giada Bargione, Claudio Vasapollo + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-88542-8

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Abstract

The striped venus clam (Chamelea gallina) is the main edible bivalve living in Italian waters. According to Regulation (EU) 2020/2237, undersized specimens (total length of the shell, < 22 mm) must be returned to the sea. C. gallina specimens of different size classes that had undergone hydraulic dredging and mechanized sorting were analysed for reburial ability in a laboratory tank and for survivability in the laboratory (135 clams, 21 days) and at sea (320 clams, 15 days). In the tank experiments, the reburial times (T50 and T90) and the upper (+) and lower (−) confidence intervals (CIs) of the whole sample were about 4 h (CI+ 4.4, CI− 3.6) and 8 h (CI+ 8.2, CI− 7.7), respectively, and were significantly shorter for the medium-sized clams (22–24.9 mm) than for the smallest (< 21.9 mm) and the largest (> 25 mm) specimens. For the field survivability experiments, clams under and above the minimum conservation reference size were placed in separate metal cages. Survival rates were 94.8% and 96.2% respectively in the laboratory and at sea, without significant differences between the two experiments or among size classes. These findings conclusively demonstrate that C. gallina specimens returned to the sea have a very high survival probability and that they can contribute to mitigate the overexploitation of natural populations.

Highlights

The striped venus clam (Chamelea gallina Linnaeus, 1758), an edible and commercially valuable bivalve, is an infaunal filter-feeding clam of the family Veneridae
Clams were harvested by a commercial hydraulic dredger (LOA, 15.8 m; tonnage, 9.7 GT; engine power, 110 kW) using standard gear and sorting methods in two fishing trips carried out in the Ancona Maritime District
The χ2 test highlighted a significantly different (p < 0.01) reburial ability depending on size class (Table 1)

Summary

Introduction

The striped venus clam (Chamelea gallina Linnaeus, 1758), an edible and commercially valuable bivalve, is an infaunal filter-feeding clam of the family Veneridae It is widespread in the Mediterranean and the Black Sea and along the eastern Atlantic coasts, where it inhabits the fine well-sorted sand biocoenosis described by Pérès and Picard[1]. Since the 1970s, technological innovations such as hydraulic dredges and mechanized sorting equipment have considerably increased the fishing effort and exploitation level of C. gallina beds in the northern Adriatic Sea, resulting in overexploitation in some areas[8] Another consequence has been the loss of the largest specimens (> 25 mm in shell total length; TL), owing to the efficiency and size selectivity of the gear, which has been estimated to catch nearly 100% of commercial-sized clams[4], as well as to inadequate stock management and protection measures[9]. The possible differences in reburying and survivability capacity across sizes were examined by studying undersized individuals (discards) as well as commercial-sized specimens

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