In situ fast marking study of manila clams (Ruditapes philippinarum)

Arcachon Bay, in the southern Bay of Biscay, is first French production area Manila clam (Ruditapes philippinarum) with an annual commercial fisheries around 400 tons recent years. This bivalve mollusc was introduced into bay 1980s for aquaculture purpose and quickly succeeded natural settlement so that its high market value led to progressive establishment a perennial fishery from mid-1990s. Local management plans applied this species are based on licensing system commercial, protected areas days prohibited fishing both recreational fishermen. A minimum catch size also prescribed by European regulation, growth rates important matter context. work focuses studying shell recapture shells, previously marked using chemical marker (calcein) then grown conditions, performed order determine patterns. clams were immersion situ seawater containing calcein. In study limitations calcein mark readability manila mortality, various exposure times, 30 minutes 1 hour, concentrations, 50 mg.L-1 200 tested. After period 35 days, 69 micro-increments observed, and, it found increment deposition occurs tidal periodicity. Moreover, showed method fast-marking clams, potentially other species, feasible situ.