Can the presence of a large conspecific improve the production and welfare of groups of smaller self-feeder competent rainbow trout?
Article first published online: 19 SEP 2011
© 2011 Blackwell Publishing Ltd
Volume 43, Issue 11, pages 1620–1627, October 2012
How to Cite
Flood, M. J., Noble, C., Kagaya, R. and Tabata, M. (2012), Can the presence of a large conspecific improve the production and welfare of groups of smaller self-feeder competent rainbow trout?. Aquaculture Research, 43: 1620–1627. doi: 10.1111/j.1365-2109.2011.02967.x
- Issue published online: 10 OCT 2012
- Article first published online: 19 SEP 2011
- Japan Society for the Promotion of Science
- rainbow trout Oncorhynchus mykiss (Walbaum), aggression;
This study examined the production and welfare effects of including a large self-feeder competent rainbow trout, Oncorhynchus mykiss (Walbaum) (~665 g) in groups of smaller self-feeder competent conspecifics (~234 g). Costs and benefits were examined for both welfare (aggression, fin damage, condition and mortality) and production (self-feeder utilization and growth). The 8-week experiment used six groups of small trout; three treatment groups containing a large trout and three control groups. After 4 weeks the large fish were removed from treatment groups and added to control groups, thus reversing the treatments. Whilst it was thought that the presence of a larger fish would suppress aggression in smaller conspecifics this did not occur. In fact aggression was significantly (P = 0.036) higher when large trout were present during the first 4 weeks. No significant differences were found between other welfare indicators, self-feeder utilization or production parameters. From a production and welfare perspective these results suggest that with the exception of initially increasing aggression larger fish do not represent a significant benefit or risk to smaller conspecifics being cultured in self-feeder equipped tanks, when all fish are self-feeder competent.