REMOULA 2000 - Réseau de croissance moule des Pertuis Charentais - Mars 2000 - Février 2001

A production monitoring network focused on the blue mussel Mytilus edulis, was developed at the Charentais sounds' geographic level to assess the spatial and temporal variability of the mussel production. Similarly to the oyster growth monitoring network REMORA, an homogeneous and calibrated mussel population (L = 35.5 mm, TW = 3.35 g) was distributed into six rearing sites, representative of the sounds production. The rearing technics were compared and intercalibrated with previous growout facilities used for preliminary trials (round bags-oyster bags). The monitoring was based upon biometric and biochemical measurements on a 3 month and monthly basis, for ail and 3 sites respectively. The mortality rates showed a significant spatial and temporal variability (7 to 22 %), with the highest values over the winter time. The net weight gains on long lines (14.3 g) were significantly higher than those within the tidal area (7.7 g to 9.4 g). Dry rneat weight trends showed a similar pattern (1.3 g vs 0.6 g) with a significant dry meat loss between September and December 2000 (# 20 %). The observed average weight gain In 2000 was below the multiple year average (1990-1994). Moreover, the mussel proximate biochemical composition showed a large temporal variability, with carbohydrates concentrations varying from 0.2 % (March 2000) to 21 % in May 2000, 40.4 to 54.5 % and 6.4 % to 10.8 % for proteins and lipids concentrations respectively. Overall, each rearing sound showed a different growth pattern, which justifies further studies. The Bay of Yves rearing area demonstrated a 1/3 growth rate compared to those measured on long-lines, therefore confirming the significant yield decrease described by mussel farmers.