Historic DNA Provides Perspective on Hatcheries and Population Structure of Chum Salmon in Prince William Sound, Alaska

Hatcheries releasing chum salmon for ranching into Prince William Sound (PWS), Alaska, started in the 1970’s and increased dramatically in the late 1980’s.  Currently, returning hatchery-produced chum salmon outnumber wild-produced fish by about 4 to 1 for a total return of 3.2 million hatchery-produced chum salmon.  Some of these hatchery-originating fish were detected in wild chum salmon streams in recent years.  One concern is that these strays may be homogenizing among-population genetic structure, a key ingredient to local adaptation and long-term persistence.  During the 1990’s, population structure among chum salmon populations in PWS was detected using allozyme data.  We proposed to examine population structure among 4 populations distributed in PWS from archival scale samples taken before the hatchery program was established and from contemporary samples screened for 188 SNP loci.  Preliminary results suggest that structure among chum salmon populations prior to the establishment of the hatchery program was similar in depth to that observed in other places of similar scale.  This structure is still present in contemporary populations, however these populations are slowly becoming more similar to the hatchery population.  Populations geographically closest to hatcheries have become more similar to the hatchery population than populations more distant from the hatcheries, a pattern that is consistent with hatchery straying observations.