Methods for the aquarium maintenance of the common octopus of British waters, Eledone cirrhosa

Abstract

Healthy, undamaged specimens survive well in recirculating aquarium seawater of about 36 parts per thousand salinity and pH 7·4, having 50 mg.l-1 nitrogen as nitrate, < 0·1 mg.l-1 nitrogen as nitrite, and < 0·1 mg.l-1 nitrogen as ammonia, and a mean annual temperature of 14-15°C, about 5°C above ambient. For maximal growth rates, the gross wet weight of live crabs required as food ranges up to 10% of the weight of the octopus. Weight-specific growth rates fall from 3-4% day-1 at 100-200 g bodyweight, to 1-1°5% day-1 at >500 g bodyweight. Survival of healthy, wild-caught animals, commonly 4-6 months and up to 8 months, is apparently limited more by endogenous factors concerned with sexual maturation and lifespan than by aquarium conditions. Eggs have been laid but it has not yet been possible to hatch and rear them.