The influence of wave frequency and wave height on the behaviour of rainbow trout ( Oncorhynchus mykiss) in cages

Abstract

The understanding of the behaviour of fish in cages is limited, yet is important for the efficient management of farmed fish. The feeding, swimming and social activity of rainbow trout, Oncorhynchus mykiss, in two cage types (rigid-cage and bag-cage), was video-taped under various wave conditions in a large wave tank. Results indicated that the amount of time spent swimming and the number of interactions between fish were significantly positively correlated with wave frequency and height. The effect of wave frequency and height on the distance between individuals and their distribution patterns was also significantly correlated. The effect of wave frequency on all the variables was stronger than the effect of wave height, and appears to be important in modifying behaviour. The influence of wave frequency and height on swimming and social interaction was higher in the bag-cage than in the rigid-cage, probably because the rigid structure of the cage dissipated some of the wave energy which resulted in less stress on the fish.