Exploring the fitness risk posed by escapes from marine aquaculture:  the OMEGA model  

The rapid development of offshore marine aquaculture worldwide has raised concerns due in part to the potential for various negative ecological and genetic impacts should farmed fish escape and mix with wild conspecifics.  Impacts due to interbreeding between wild fish and escapees 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 farmed) population, making it potentially less able to respond to stochastic changes or long-term trends (e.g. climate change) in environmental conditions.  

Risk is a function of 1) the number of escapees relative to wild census size, 2) the genetic difference between escapees and wild fish, and 3) the fitness of escapees relative to wild fish.  There is little scientific data, however, that reliably assigns the risk to population fitness due to escapes.  Thus, existing regulatory standards that address escapes are largely preventative, theoretical, or qualitative rather than quantitative.  To address this knowledge gap, the NOAA Fisheries Office of Aquaculture developed the Offshore Mariculture Escapes Genetics Assessment (OMEGA) model in collaboration with ICF International to simulate the risk posed by escaped farmed fish.  OMEGA is intended to provide insight into the variables affecting risk, help identify information gaps and research priorities, explore options for design or modification of culture programs, such that the aquaculture industry itself can will drive improvements in culture techniques and sustainability, and inform policy and management decisions.  To illustrate OMEGA's application, we present results from evaluations of a theoretical sablefish (Anoplopoma fimbria) aquaculture program (originally used for model verification) and a real world pilot project for Almaco jack (Seriola rivoliana) in Hawaii (Figure 1).  Current work is directed at making OMEGA fully operational and includes fostering external collaborations to develop model scenarios, evaluate model parameters, and validate the model with data from current and planned domestic and international aquaculture operations.