Phenotypic correlations among behaviour and growth variables in tilapia: Implications for domestication selection

We have estimated the phenotypic correlation between growth rate and interactive behavior in a laboratory population of hybrid tilapia (O. mossambicus × hornorum). Observations were made on growth and several measures of interactive behavior (in both high and low competitive feeding situations) in group-reared juveniles over 52 days. Growth was not food-limited. Four feeding behavior variables: BITES, BOUTS, LATENCY, and FFI plus one agonistic behavior variable, DONOR, were significantly correlated with size-specific growth rate. The total proportion of growth rate variance “explained” by the observed behavior (R2) was high, ranging from 0.69 to 0.82. The correlations were quantitatively, but not qualitatively influenced by the size of the individual relative to its competitors. Growth was positively correlated with measures of the intensity of feeding activity, and negatively correlated with agonistic behavior. Sex accounted for significant growth rate variation but for almost no behavioral variation. On the basis of these phenotypic correlations we suggest that agonistic interaction (aggression) in this tilapia is unlikely to be indirectly selected for during simple growth rate selection of fish reared under adequate food resource conditions.