OPPORTUNITIES AND PITFALLS FOR CONSERVATION AQUACULTURE IN A WARMING WORLD:  PACIFIC COD AS A CASE STUDY  

Phenotypic variation due to underlying heritable genetic variability is the raw material through which populations and species respond and adapt to environmental change.  In the case of selective breeding (artificial selection), organisms with desirable traits are intentionally bred to produce offspring with a higher frequency of these or further enhanced traits.  Although artificial selection in aquaculture is employed to improve traits, such as resource efficiency, disease resistance, or temperature tolerances, it exploits variability that is naturally occurring.  In the wild, this variability may confer resilience to unfavorable marine conditions like warming ocean temperatures or ocean acidification associated with climate change.

We assessed selective differentiation among commercially exploited coastal Pacific cod (Gadus macrocephalus) populations and a rapidly declining population in the Puget Sound, which has experienced a much different thermal regime than coastal or northern stocks. We present data from genome-wide RAD sequencing surveys of these populations (Fig. 1), and results indicated that Puget Sound cod may be adapted to local conditions.  Local adaptation increases the biocomplexity of a species, which can help prevent extreme abundance fluctuations.  Moreover, populations at the southern edge of a species' distribution may harbor genetic variation important for the evolution of a species under warming conditions.  However, Puget Sound cod are a geographically restricted population, and while fisheries were certainly a factor in its initial decline, warming conditions in the Sound may now prevent recovery.  Because Puget Sound Pacific cod may be a reservoir of adaptively important variability, with the potential for increasing species resiliency in the face of environmental change, their conservation is key.  Can this variability be exploited commercially or for enhancement before it is too late?  A fast response to selection in captivity may suggest an equally fast response in the wild, but only if sufficient genetic variability exists.