Etudes

Etude 2

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Étude expérimentale de la prédation de la palourde japonaise,
Ruditapes philippinarum., par la dorade royale,
Sparus aurata, et le baliste, Balistes capriscus
Abstract
Résumé
René Robert (1) et René Parra (2)
(1) IF’REjlER, quai du commandant Silhouette, 33120 Arcachon. FraI/Cf.
(2) lnj/Îlut t:l/iursilairr de Bio!oy,ir .11arine, 2 rue du Pro/mmr ]/J[yel, 33120 ArWc!WIl, France.
Reçu le 17 dC’C’cmbrc 1 rJ!)o; accepté le fi mai 1991.
Experimental study of predation by the gilthead bream, Sparus aurata and the gray triggerfish, Balistes
capriseus on the ManiJa clam Rue/irapes philippinarum.
Rohert R., R. Parra. Aquat. Ut’Îng Resour., 1991,4. 181-189.
Since 1988, heavy mortality of reared Manila clam Ruditapes philippinarurn have heen observed in
the basin of Arcachon. Clam predation by the gilthead bream Sparus aurata and the gray triggerfish
Balistes capriscus has been suspected. Thcrefore, an experimental study of predation on Ihis dam by
these two fish has been carried out. Feeding rates were determined according to the size of clams,
temperature and degree of protection. The amount of clams ingested varied with the size of predator
and prey but bath fish were serious clam predator. A daily ingestion of 500 sccd and 350 spa! has
been recorded, 50 to 70% of the prey being eaten during the first 6 hours. Beeause clams were
generally communited by thcse two fish and bottom marks quite similar, it was not possible ta
diseriminate the intervention ofboth predators. When water temperature was below 16’C, an important
decrease in the feeding activity was observed. A net protection may be used to prevent this kind of
predation. The Manila clam mortalities, recorded during the summer period in the basin of Arcachon,
ean be attributed, to a certain extend, to the intervention of these fish. Sparus aura ta is a clam
predator but the occurrence of the gray triggerfish Balistes capriscus in the basin of Arcachon is a
serious concern because this is a vigorous species which Îs not commercialy fished and then out of
control.
Keywords : Sparus aurata, Balistes capriscus, Ruditapes philippinarum, Manila clam, predation

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