EFFECT OF ALEWIFE PREDATION ON SURVIVAL OF LARVAL YELLOW PERCH IN AN EMBAYMENT OF LAKE-ONTARIO

We examined the effect of alewife predation on larval yellow perch bet ween 1984 and 1986 in North Pond and South Pond, embayments of Lake On tario. The ponds provided a natural experiment; larval yellow perch oc curred in both ponds, but alewife occurred only in North Pond. Alewife consumed yellow perch larvae during late April and early May in North Pond in 1985 and 1986. In 1984, alewife immigrated into North Pond 3 weeks after the peak hatch of yellow perch and predation was not obser ved. Instantaneous daily mortality rates of larval yellow perch were h igher in North Pond in 1985 (1.58) than in South Pond in all 3 years ( 0.22-0.28) and coincided with the highest alewife abundance of the 3 y ears. Temperature, wind events, and food availability could not direct ly account for the high larval mortality rate. A predator-prey model f urther supported our findings; alewife predation was sufficient to acc ount for the high larval mortality rate. Predation by alewife appears to be a source of significant larval yellow perch mortality in North P ond and could effect the recruitment of yellow perch in Lake Ontario.