UNDER-ICE OBSERVATIONS OF BEHAVIOR OF SELECTED NATIVE AND EXOTIC FISHES OF THE ST-LAWRENCE-RIVER SYSTEM

Winter behavior of two native fishes (yellow perch, Perca flavescens, and killifish, Fundulus heteroclitus) and an exotic (goldfish, Carassi us auratus) were studied in an outdoor experimental pond to quantify a nd link behavior to environmental conditions, and to identify interact ions among the species that now co-occur in the wild. Killifish had hi gh mortality and were not observed. However, contrary to our predictio ns, perch and goldfish had good overwinter survival and remained activ e in winter, and neither species spent most of their time in the warme st layer of the water column. Only two instances of aggression were se en: in both, goldfish charged perch. Both species were found principal ly in groups (schools); goldfish spent 18% of their time in multispeci es groups.