MICROGEOGRAPHIC VARIABILITY IN FEEDING, ABSORPTION, AND CONDITION OF MUSSELS (MYTILUS-GALLOPROVINCIALIS LMK) - A TRANSPLANT EXPERIMENT

Mussels, Mytilus galloprovincialis Lmk., were reciprocally transplante d between three cultivation rafts in the Ria de Arousa (Galicia, north west Spain). After an 8-wk period, rafts were visited and individual m easurements of clearance rate, absorption efficiency, and condition in dex were performed in the field under ambient conditions of temperatur e, salinity, and food availability. Clearance rate standardized to a c ommon shell length was not significantly affected by the location of m ussels in the Ria but varied according to their origin. Absorption eff iciency was mainly affected by raft position, reflecting the spatial v ariability in the quality of available food. Origin-related difference s in absorption efficiency showed the same trend as recorded for clear ance rates. No gradient of environmental factors has been recorded in the Ria that might account for differences in physiologic parameters p ersistent after transplantation (i.e., origin effects). Associated evi dence suggests that observed differences may have resulted from spatia l variability in the degree of parasitic infestation. Condition index was dependent on both raft position and mussel origin and closely refl ected the described variability in physiological parameters. Remaining variability in condition index can be attributed to different conditi ons before transplantation took place.