Physiological responses of the Chilean scallop Argopecten purpuratus to decreasing salinities

Abstract

Argopecten purpuratus (Chilean scallop) is a filter-feeding bivalve which inhabits sheltered areas of the north and central Chile. Considering that culture of this species has started in the south of Chile, it is of great interest to know the tolerance of this bivalve to conditions of decreasing salinity, which can occur in these locations. For this purpose, different physiological processes related to the acquisition and utilisation of energy (clearance rate, absorption, oxygen uptake and excretion) were measured at different salinities (30, 27, 24, 21 and 18‰) on a wide range of body size after the scallops had been acclimatised to the experimental salinities for a week at 12°C. Clearance rate showed higher and similar values at 30 and 27‰, decreasing significantly at the lower salinities. Oxygen uptake increased with decreasing salinity from 30 to 24‰, showing the lowest value at the extreme condition of 18‰. A similar pattern was presented by the excretion rate, which also increased within the range 30-24‰, to show a reduction with decreasing salinities. The O/N ratio also decreased with reduction in salinity in the 5 and 10 g size classes. A negative relationship was observed between the size of A. purpuratus and the O/N ratio. Scope for growth was highly affected by low salinities, with positive values only between 27 and 30‰. Negative scope for growth was observed at all the other experimental salinities. The data obtained suggest that the selection of sites to cultivate this species must take into consideration the tolerance of this species to the salinity, and positive growth rates can be expected at salinities over 27‰.