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Can the presence of a large conspecific improve the production and welfare of groups of smaller self‐feeder competent rainbow trout?
Author(s) -
Flood Matthew J.,
Noble Chris,
Kagaya Rem,
Tabata Mitsuo
Publication year - 2012
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.2011.02967.x
Subject(s) - rainbow trout , aggression , biology , trout , welfare , fish <actinopterygii> , fishery , production (economics) , animal welfare , zoology , ecology , toxicology , psychology , social psychology , microeconomics , economics , market economy
This study examined the production and welfare effects of including a large self‐feeder competent rainbow trout, O ncorhynchus mykiss ( W albaum) (~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.