Reproductive success of captively bred and naturally spawned Chinook salmon colonizing newly accessible habitat.

Reproductive success of captively bred and naturally spawned Chinook salmon colonizing newly accessible habitat.

Evol Appl. 2013 Feb;6(2):165-79

Authors: Anderson JH, Faulds PL, Atlas WI, Quinn TP

Abstract
Captively reared animals can provide an immediate demographic boost in reintroduction programs, but may also reduce the fitness of colonizing populations. Construction of a fish passage facility at Landsburg Diversion Dam on the Cedar River, WA, USA, provided a unique opportunity to explore this trade-off. We thoroughly sampled adult Chinook salmon () at the onset of colonization (2003-2009), constructed a pedigree from genotypes at 10 microsatellite loci, and calculated reproductive success (RS) as the total number of returning adult offspring. Hatchery males were consistently but not significantly less productive than naturally spawned males (range in relative RS: 0.70-0.90), but the pattern for females varied between years. The sex ratio was heavily biased toward males; therefore, inclusion of the hatchery males increased the risk of a genetic fitness cost with little demographic benefit. Measurements of natural selection indicated that larger salmon had higher RS than smaller fish. Fish that arrived early to the spawning grounds tended to be more productive than later fish, although in some years, RS was maximized at intermediate dates. Our results underscore the importance of natural and sexual selection in promoting adaptation during reintroductions.

PMID: 23467446 [PubMed – in process]

via pubmed: school of aquatic an… http://www.ncbi.nlm.nih.gov/PubMed/23467446?dopt=Abstract

Dispersal and tributary immigration by juvenile coho salmon contribute to spatial expansion during colonisation

Joseph H. Anderson, George R. Pess, Peter M. Kiffney, Todd R. Bennett, Paul L. Faulds, William I. Atlas*, Thomas P. Quinn

Accepted for publication July 12, 2012

Abstract
Anadromous fishes are frequently restricted by artificial barriers to movement such as dams and culverts, so measuring dispersal helps identify sites where improved connectivity could promote range expansion and population viability. We used a combination of DNA-based parentage analysis and mark–recapture techniques to evaluate dispersal by juvenile coho salmon (Oncorhynchus kisutch) in a population in the initial stages of colonisation following installation of fish passage structures at a previously impassable dam on the Cedar River,
WA, USA. The spatial distribution of individuals within maternal families revealed that dispersal was common. Among the offspring of radio-tagged mothers, 28% were collected outside the spawning reach and dispersed up to
6.3 km (median = 1.5 km). Most juveniles captured in a tributary (Rock Creek, where few adults spawned) had immigrated from the Cedar River and represented many different families. Juvenile dispersal therefore provided a
secondary phase of spatial expansion following initial colonisation by adults. Consistent with the conditiondependent dispersal hypothesis, juveniles that dispersed farther upstream in the tributary were larger than fish collected near the tributary mouth. Overall, the results demonstrated widespread dispersal in a system with low coho salmon densities, and this might increase the rate of population growth if it reduces the effects of local density dependence. By implication, juveniles can take advantage of rearing habitats reconnected through barrier removal, even when such areas are located several kilometres from adult breeding grounds.

Key words: movement, condition dependence, reintroduction, parentage, pedigree, dams

School of Aquatic and Fishery Sciences

Reproductive success of captively bred and naturally spawned Chinook salmon colonizing newly accessible habitat.