ScholarWorks@UNO

Diet of invasive Rio Grande cichlids (Herichthys cyanoguttatus) in Louisiana: habitat effects and implications for native species

Rio Grande cichlids (Herichthys cyanoguttatus) are non-native fish introduced into the Greater New Orleans Metropolitan Area (GNOMA) over 20 years ago. They have spread widely and their presence has been shown to impact native fishes. This species occurs in a variety of habitats, including cypress swamps, bayous, and concrete canals which indicates a potential concern for future spread. We examined the diet of H. cyanoguttatus to determine: 1. the breadth of their diet in these habitats; 2. potential diet overlap with native species; and 3. the possibility of H. cyanoguttatus predation on native species. We collected over 200 H. cyanoguttatus from GNOMA and surrounding areas. Half of these fish were from concrete canals and half were from sites with relatively natural substrates and vegetation. We also placed Hester-Dendy invertebrate traps at certain sites to determine prey availability. Cichlids collected from concrete canals exhibited a narrow diet consisting mostly of algae. Cichlids from more natural habitats exhibited more varied diets which included prey such as crayfish, fish scales, fish eggs, various arthropods, and mollusks. When H. cyanoguttatus diet was compared with available invertebrate prey items (as measured by Hester-Dendy sampling), it appears that cichlids are preferentially feeding on mollusks and crustaceans. These data indicate that the diet of H. cyanoguttatus is variable and that this species consumes native organisms such as crayfish and other fishes. We also found that the diet of some co-occurring native fishes overlaps with that of H. cyanoguttatus suggesting that they may be impacted by this invasive species.