Modeling the variable effects of using wild and cultured broodstock on the fitness risk due to escaped farmed fish
2017
Gruenthal, K.M. (Earth Resources Technology, Inc., NOAA Fisheries Office of Aquaculture, MD (U.S.A.)) | Volk, J.D. | Blair, G.R. | Key, G. | Rust, M.B.
Various negative ecological and genetic impacts may occur when farmed fish escape and mix with wild conspecifics. Genetic impacts result due to interbreeding between wild fish and escapees and may result in reduced genetic diversity within and among populations and a loss of fitness. Loss of genetic diversity and fitness compromise the adaptive potential of a mixed (wild plus cultured) population, making it potentially less able to respond to changes in environmental conditions (e.g. climate change). Simplified, risk to wild population fitness due to interbreeding with escapees is a function of the number of escapees relative to wild census size, the genetic difference between escapees and wild fish, and the fitness of escapees in the wild relative to wild fish. The Offshore Mariculture Escapes Genetics Assessment (OMEGA) model simulates the magnitude of this risk. To illustrate OMEGA's application, we present results from evaluations of a planned pilot project for Almaco jack (Seriola rivoliana) in Hawaii and contrast them with those obtained from evaluation of a theoretical sablefish (Anoplopoma fimbria) aquaculture program originally used to verify the model. Escape scenarios for both species varied from low to high base leak rates, cage failure probabilities, and catastrophic cage failure probabilities. Whereas the high escapes scenario for sablefish resulted in a significant impact to wild population fitness, even a total loss of almaco jack had a negligible effect. Key differences in the simulated fitness risk associated with each program included, but are not limited to, broodstock source (domesticated or wild), encounter rate between wild fish and escapees, and the scale (size and longevity) of the operation.
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