The use of physiological assessment techniques for determining the relative activity rates of bivalve shellfish during simulated depuration

A series of trials were undertaken over an 18-month period to determine the relative activity rates for mussels (Mytilus edulis), Pacific oysters (Cra ssostrea gigas), native oysters (Ostrea edulis), cockles (Cerastoderma edul e), and Manila clams (Tapes philippinarum) subjected to varying seawater te mperatures and dissolved oxygen levels. All these species are currently com mercially depurated in the UK. To achieve this, alternative techniques to t he more traditional use of bacteriological analysis were used to establish the physiological response of bivalve mollusks to varying conditions. These were the monitoring of ammonia excretion, consumption of dissolved oxygen, and uptake of a neutral red dye. The monitoring of ammonia excretion corre lated with dissolved oxygen consumption, and these proved to be useful meth ods of obtaining information on the physiological response of bivalve mollu sks subject to varying simulated depuration conditions. The information obt ained could not have been achieved by bacteriological analysis. However, th e dye test, although already an established method, did not prove to be ent irely satisfactory. Overall, the results found that both species of oyster were much less active than the other species, which may have implications f or depuration systems.