Illinois Natural History Survey - University of Illinois

Development and Application of a Gambusia Bioenergetic Model

Mosquitofish, Gambusia affinis, are one of the most widely introduced freshwater fish in the world. Gambusia's reputation as a mosquito control agent has been the impetus for large-scale introductions of the species. Their ability to tolerate a broad range of temperatures, salinities, and dissolved oxygen concentrations, combined with their prolific reproductive potential, enable mosquitofish to become easily established in non-native habitats. Establishment of Gambusia populations in non-native habitats, however, has also resulted in negative impacts for many native cyprinids.  To facilitate management questions regarding appropriate densities and habitats to introduce mosquito-fish as well as understand the ecological role of these fishes, better knowledge of their feeding requirements and growth dynamics is needed.

Mosquitofish, Gambusia affinis.

Development and corroboration of a Gambusia bioenergetic model is a first step to providing a tool that could be used to study resource demand and growth dynamics in mosquitofish. Based on laws of thermodynamics, bio-energetic models represent mass balance equations that link energy intake to energy expenditures. In generalized form, bioenergetic models can be expressed as,

consumption = (metabolism) + (wastes) + (growth).

Each of these physiological processes can be independently measured in the laboratory and is generally expressed as a function of body size and water temperature. External variables, such as water temperature, diet, and fish growth rate, are then measured in the field and used as input to the model to estimate food consumption.

Using published information and results from laboratory studies conducted at the INHS Sam Parr Biological Station, we are developing and testing a bioenergetic model for Gambusia. In a series of feeding trials, we found that Gambusia feeding rates were highest at water temperatures ranging from 30 to 35deg.C. At these temperatures, specific consumption rate by Gambusia was relatively high and ranged from 34% to 175% (g dry wt prey/g-1dry wt Gambusia d-1) for Gambusia-fed chironomids. We are using these data and information on Gambusia metabolic rates in the bioenergetic model to estimate seasonal energy requirements of mosquitofish. In additionwe are evaluating model performance using independently derived field estimates of Gambusia feeding rates. We are quantifying seasonal growth and food consumption of a local Gambusia population and comparing field-derived consumption estimates to those predicted by the bioenergetic model. We anticipate that development and corroboration of a Gambusiabioenergetic model will provide a useful tool for addressing a variety of ecological and management questions regarding the common mosquitofish.

Steven R. Chipps, Michelle A. Bouchard, and David H. Wahl, Center for Aquatic Ecology

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