The Rio Grande cichlid (Herichthys cyanoguttatus) has been established in the Greater New Orleans Metropolitan area for at least 20 years, and its effect on native fishes is unknown. Behavioral trials were performed to determine if aggressive interactions occur between invasive H. cyanoguttatus and native bluegill (Lepomis macrochirus). When defending a territory as the resident, L. macrochirus were markedly aggressive, averaging 11.6 aggressive actions per 10-min behavioral trial. In contrast, L. macrochirus were extremely passive as invaders, with 0.5 aggressive actions per trial. Herichthys cyanoguttatus were equally aggressive as residents and as invaders, averaging 4.9 and 6.0 aggressive actions per trial, respectively. Herichthys cyanoguttatus interacted aggressively with native species whether they held territory or not, indicating that this invasive species may have fundamentally different strategies of aggression compared with native L. macrochirus. These differences may explain the continued success of H. cyanoguttatus as an invasive fish in southeastern Louisiana.

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The Rio Grande cichlid (Herichthys cyanoguttatus) is a non-native fish that has become established in the greater New Orleans metropolitan area. We conducted laboratory experiments to determine if H. cyanoguttatus growth was impacted either by salinity or the presence of bluegill (Lepomis macrochirus), a native fish. There was no significant difference in growth ofH. cyanoguttatus held at three different salinities (0,8, and 16 psu) for 14 d. When H. cyanoguttatm and L, macrochirus were held at 0 psu for 28 d both with and without the other species present (n = 6 per trial), there was a significant difference in growth between species. Lepomis macrochirus held on their own grew faster than H. cyanoguttatus on their own and faster than H. cyanoguttatus held with L. macrochirus @ < 0.005). Also, L. macrochirus housed with H. cyanoguttatus grew faster than H. cyanoguttatus on their own and faster than H. cyanoguttatus with L. macrochirus (p < 0.001). A second 28 d trial compared growth of individual H. cyanogutatus and L. macrochirus held together with different relative sizes (half with a larger H. cyanoguttatus as invader [n=7]; half with a smaller H. cyanoguttatus as invader [n=7]). This experiment showed no significant difference in growth between the species (g = 0.064). These results indicate that salinity levels will not limit H. cyanoguttatus dispersal in southeastern Louisiana, while biotic resistance in the form of native L. macrochirus may or may not impact growth of this non-native species.

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Invasive Creole Painted Crayfish (Orconectes palmeri) have spread throughout the Flint River and are currently moving from there into a tributary, Muckalee Creek. The negative behavioral impact of the invasive is a concern for the endemic Muckalee Crayfish (Procambarus gibbus). Tests examining residence, size, and cover effects on aggression demonstrated that O. palmeri is a dominant species in these encounters. This may explain the success of O. palmeri in the Flint River with Procambarus spiculifer, which is a close relative of P. gibbus, and it may also mean the endemic P. gibbus is in danger of extirpation. A survey of the Muckalee showed O. palmeri has already entered the tributary and are likely spreading upstream.