Complex Interactions between Native and Invasive Fish: The Simultaneous Effects of Multiple Negative Interactions

• Published in: Oecologia Vol. 141; no. 4; pp. 713 - 721
• Main Authors: Mills, Michael D., Rader, Russell B., Belk, Mark C.
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.12.2004; Springer; Springer Nature B.V
• Subjects: Analysis of Variance; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Body Size; Community Ecology; Competition; Competitive Behavior - physiology; Cyprinidae - anatomy & histology; Cyprinidae - physiology; Cyprinodontiformes - anatomy & histology; Cyprinodontiformes - physiology; Desert Climate; Ecological competition; Ecosystem; Fish; Fresh water ecosystems; Freshwater; Freshwater fishes; Fundamental and applied biological sciences. Psychology; Gambusia affinis; Habitat selection; Indigenous species; Invasive fish; Invasive species; Invertebrates; Iotichthys phlegethontis; Mortality; Native species; Population Density; Population Dynamics; Potamogeton; Predation; Predators; Predatory Behavior - physiology; Refuge habitats; Risk reduction; Species extinction; Synecology; Utah; Wildlife habitats; Utah; Competition; Biological invasions; Invasion; Freshwater environment; Iotichthys phlegethontis; Vertebrata; Invasive species; Pisces; Interspecific competition; Predation; Gambusia affinis; Native species; Interspecific relation
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-004-1695-z

We suggest that the ultimate outcome of interactions between native species and invasive species (extinction or coexistence) depends on the number of simultaneous negative interactions (competition and predation), which depends on relative body sizes of the species. Multiple simultaneous interactions may constrain the ability of native species to trade fitness components (i.e., reduced growth for reduced risk of predation) causing a spiral to extinction. We found evidence for five types of interactions between the adults and juveniles of introduced western mosquitofish (Gambusia affinis) and the juveniles of native least chub (Iotichthys phlegethontis). We added ten large (23-28 mm) and seven small (9-13 mm) young-of-the-year (YOY) least chub to replicate enclosures with zero, low, and high densities of mosquitofish in a desert spring ecosystem. Treatments with mosquitofish reduced the average survival of least chub by one-third. No small YOY least chub survived in enclosures with high mosquitofish densities. We also performed two laboratory experiments to determine mortality to predation, aggressiveness, and habitat selection of least chub in the presence of mosquitofish. Mean mortality of least chub due to predation by large mosquitofish was 69.7% over a 3-h trial. Least chub were less aggressive, selected protected habitats (Potamogeton spp.), and were more stationary in the presence of mosquitofish where the dominance hierarchy was large mosquitofish>>arge least chub≈small mosquitofish>>small least chub. Least chub juveniles appear to be figuratively caught in a vice. Rapid growth to a size refuge could reduce the risk of predation, but the simultaneous effects of competition decreased least chub growth and prolonged the period when juveniles were vulnerable to mosquitofish predation.