Growth of seed mussel (Mytilus galloprovincialis LMK): Effects of environmental parameters and seed origin

Abstract

Mussel seeds (Mytilus galloprovincialis Lmk) of similar weight and length from two different origins (rocky shore and collector ropes) were cultivated on a raft in the Ria de Arousa (northwest Spain), from seeding to thinning out, for a total period of 208 days (November 1995 through July 1996). Weight increase rates for the seed from collector ropes were higher than those for the seed from rocky shore, and the growth rate variations during the cultivation period were associated with the environmental parameters measured (chlorophyll a and temperature). The origin of the seed was also found to be a significant factor. The condition index (CI) of the seed from collector ropes was significantly greater than that of the rocky shore seed at the beginning of the cultivation time. Both mussel seeds showed a similar CI after 70 days and during the rest of the cultivation time. Although allometric coefficient values for the relation total dry weight-length showed a similar range for both types of seed, no significant differences were observed for this coefficient in collector rope mussels throughout the cultivation period. Rocky shore mussels showed, on the contrary, a significant increase for this allometric coefficient value throughout the cultivation period. These preliminary results from the total dry weight-length relationship obtained here and the change of CI differences serve to strengthen the hypothesis of a physiological basis for the differences in growth between both types of seed mussel. This finding could be related to the different features of the original habitats of the two types of seed, in terms of the cycles of availability of food and exposure to the air.