VARIATION IN AGONISTIC BEHAVIOR BETWEEN NEWLY EMERGED JUVENILES FROM HATCHERY AND WILD POPULATIONS OF COHO SALMON, ONCORHYNCHUS-KISUTCH

Hatchery juveniles were more aggressive than wild juveniles. Rates of aggressive display increased with time since emergence for both hatchery and wild fish, as did the differences in behavior between the 2 types. By 13 d postemergence, the overall effect of fish type was highly significant for all aggressive behaviors. Differences are presumably genetic. Comparisons involved relatively few families from each population. However, because heritability was moderate to low within populations, and variance between population types exceeded variance among families within populations, these results indicate real differences at the population level. -from Authors