Use of Genetic Variation in Recovery of Chinook Salmon in the Nooksack River

A baseline was constructed for three Chinook salmon populations in the Nooksack River.  Total spawning escapement was estimated from redd and carcass counts, and allocated among the three populations according to the proportion of carcasses assigned to each of the three populations. 

A captive-brood program was initiated to reverse a rapid decline in the South Fork Nooksack population of Chinook salmon.  Natural-origin juvenile Chinook salmon collected in the South Fork of the Nooksack River were matched to the three populations through individual assignment.  South Fork population individuals were retained and reared to maturity in captivity, others were released.  After sufficient growth, retained South Fork juveniles were PIT-tagged and tissue for DNA was taken.  Samples were genotyped at 14 microsatellite loci and relatedness was estimated.  Relatedness estimates were used to design a breeding matrix to avoid inbreeding and maintain overall genetic diversity in the captive population.

Rarefaction analysis applied to the inferred parentage of all fish screened for the captive brood program was used to estimate the number of successful spawners across all populations.  Kinship-based estimates of successful spawners ranged from 150% to 340% of the originally estimated adult escapement based on visual monitoring methods using redd surveys and carcass counts.