SEASONAL-VARIATION IN THE CONDITION OF SOME INTER-TIDAL INVERTEBRATES OF THE YTHAN ESTUARY, SCOTLAND

Changes in the 'body condition' (calorific values, weight of standard sized animals and the number of calories they contain) have been studied over a period of one year for a variety of intertidal invertebrates in the Ythan Estuary. The highest calorific values exceed the lowest by factors ranging from 1·05 to 1·27. The maxima for body weights and numbers of calories exceed the minima by factors ranging from 1·2 to 5·5, with most being in the range 1·5-2·5. The peaks of condition generally occurred in May-July or October-November and changes in condition are probably due to a combination of the reproductive and nutritional status of the animals. Predators of these invertebrates will have to vary the number of prey items they eat, according to the condition of the prey, in order to obtain minimal ingestion requirements. © 1979.