EFFECTS OF GREEN SUNFISH (LEPOMIS-CYANELLUS) PREDATION ON SURVIVAL AND HABITAT USE OF PLAINS KILLIFISH (FUNDULUS-ZEBRINUS)

Predation by green sunfish (Lepomis cyanellus) on plains killifish (Fu ndulus zebrinus) may explain why these species rarely co-occur in pool s of intermittent Purgatoire River tributaries in southeastern Colorad o. Large green sunfish ate 16% of plains killifish during a 24-h exper iment in tanks which provided shallow and deep water, with and without simulated vegetation cover, similar to natural pools. Killifish use o f deep water or cover during daylight did not differ significantly in tanks with green sunfish versus those without. No killifish were found in stomachs of test sunfish or those captured in tributary pools duri ng daytime, but this was probably due to crepuscular feeding combined with high gastric evacuation rates. Plains killifish co-occurred with green sunfish in significantly fewer tributary pools than expected by chance in both 1987 to 1988 and 1993 to 1994. Together, our experiment al and field data support the hypothesis that green sunfish can reduce or eliminate plains killifish in isolated pools.