GROWTH PERFORMANCE OF OYSTER Ostrea edulis AND Crassostrea gigas CULTURED IN THE OPEN OCEAN OF THE SOUTHEASTERN BAY OF BISCAY
Unai Aldalur1, Beñat Zaldibar2 and Izaskun Zorita1
1AZTI-Tecnalia; Marine Research Division; Herrera Kaia, Portualdea z/g; 20110 Pasaia; Gipuzkoa, Spain.
2CBET Research Grp, Dept Zoology and Animal Cell Biology, Sci and Technol Fac and Research Centre for Experimental Marine Biology and Biotechnology (PIE- UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, E-48080 Bilbao, Basque Country, Spain.
E-mail: ualdalur@azti.es
Keyword: Offshore aquaculture, Oyster culture, long-line, Crassostrea gigas, Ostrea edulis.
Oyster culture industry is nowadays restricted to sheltered areas, and its expansion is constrained by conflicts with other uses, thence, offshore aquaculture is a promising opportunity to expand the bivalve culture operations, minimizing environmental impacts and conflicts with other uses.
Despite the growing interest on offshore aquaculture, information about the feasibility of oysters in open ocean conditions is limited. Therefore, the aim of this study is to assess the growth performance of the European flat oyster (Ostrea edulis) and the Pacific oyster (Crassostrea gigas) cultured in the offshore environment of the southeastern Bay of Biscay.
Oysters were cultured in submerged long-line systems through suspended lanterns at an experimental offshore site during 19 months. Together with physical/chemical parameters (including Chloropylla, temperature POC and TPM) oysters were collected and shell length and fresh weight were monthly determined.
Despite the low chlorophyll concentrations (mean = 0.56 µg/l) measured, both oyster species showed a good growth performance, comparable to rates observed in both nearshore and offshore farms. Ostrea edulis grew from 28 mm to 76 mm in length and from 1.6 g to 53.7 g in fresh weight. On the other hand, Crassostrea gigas presented faster growth rates ranging from 26 mm to 114 mm in length and from 1.6 g to 112.1 g in fresh weight. These results indicate that offshore oyster production is biologically and technically feasible in the Southeastern Bay of Biscay and may be an alternative to reduce environmental impacts.
Acknowledgments: This work was partially supported by the Basque Government and a PhD. grant from the AZTI Foundation.