Surviving The Cold: A Case Study on Competition Between Native Lepomis macrochirus and Invasive Herichthys cyanoguttatus for Overwinter Habitat Use

Abstract

Invasive species management can be challenging or even impossible, especially in aquatic environments. To determine if the tropical origins of an invasive species affected where it could be targeted, we constructed a study to compare winter behavior of a tropical, invasive species to a temperate weather, native species in Louisiana. The winter activity and cold tolerance of ten invasive Rio Grande Cichlids, Herichthys cyanoguttatus and ten native bluegill, Lepomis macrochirus was observed using an outdoor pond with a dual antenna PIT tag array and an artificial culvert created inside of the pond. All fishes had PIT tags injected into their lateral musculature. Both species were active at temperatures below 10°C and all twenty fish survived temperatures as low as 7°C. Even though the invasive H. cyanoguttatus is a member of a tropical family of fishes, activity and even feeding behavior of both species was similar up to 13°C; but H. cyanoguttatus individuals were more active than L. macrochirus at higher temperatures. Both species appeared to use the culvert during cold fronts, demonstrating that the behavior of both species during cold weather were remarkably similar. This study illustrates the thermal tolerance abilities of H. cyanoguttatus in New Orleans and also demonstrates their potential for invading other cold-water habitats. Significance Statement This article is the first to investigate the simultaneous examination of overwintering behavior of a temperate native species of fish and an invasive tropical species of fish. Its application to invasive species management has unique usefulness not previously published. It is also unique in its examination of overwintering fish behavior in general, using a mesocosm PIT tag array.