Modeling the Relationship between Environmental Temperature and Feeding Performance in Florida (USA) Nonnative Fishes, with Implications for Invasive-Species Response to Climate Change

Abstract

Aims: To determine the effect of environmental temperature on the feeding kinematics of two Florida (USA) invasive-fish species, pike killifish Belonesox belizanus and Mayan cichlid Cichlasoma urophthalmus, in an attempt to explore the adaptive response of whole-organism performance to climate change. Study Design: Model I (Fixed-Effects Model) Linear Regression Analysis, y-Dependent Variable = Kinematics; x-Independent Variable = Environmental Temperature. Place and Duration of Study: Fish Ecophysiology Laboratory, Department of Biological Sciences, Florida Institute of Technology in May-December, 2011. Methodology: Four each of B. belizanus and C. urophthalmus, collected from invasive populations in Florida were acclimated in 38 liter experimental aquarium, trained, and filmed using high-speed video while eating fish-prey at 20°C, 25°C and 30°C. Four films per invasive-fish species at each temperature were analyzed using MaxTRAQ digitizing software. In each film, three kinematic-excursion (peak gape, peak hyoid depression and cranial elevation at peak gape) and three kinematic-timing (time to peak gape, hyoid depression, and cranial elevation) variables were measured. Each kinematic variable was regressed against temperature to model the relationship between feeding performance and environmental temperature. Results: All experimental fishes behaved normally and fed aggressively in each of the three experimental temperature regimes. It is evident in the feeding kinematics-temperature plots that fish-feeding at each temperature was variable and unpredictable. Out of the 12 regression equations generated to model the relationship between feeding kinematics and environmental temperature, only one (peak gape in C. urophthalmus) showed a significant slope (Peak Gape = 1.42 + 0.01 Temperature; R2 = 0.22; P< 0.01). Conclusion: The models defining the relationship between feeding kinematics and environmental temperature are weak, as indicated by the extremely low values of the coefficient of determination (R2). Empirical evidence indicates that the feeding performance of invasive B. belizanus and C. urophthalmus is not affected by temperature.