Quick Dips

Studying Sacramento Salmon

New Zealand's chinook (or quinnat) salmon originate from stock imported almost 100 years ago from the Sacramento River in North America. Fisheries biologists at NIWA (the National Institute of Water and Atmospheric Research) are taking advantage of this fact to study the differing effects of genetic and environmental influences on this recreationally and commercially important species. With the help of a five-year FRST grant, NIWA has recently launched JUNIPEX, the Joint University of Washington/NIWA Salmon Populations Experiment, designed to examine evolutionary processes in salmon.

Chinook salmon display a wide variation in basic life history traits such as age at maturity, size at age, and spawning date. Previous work has shown differences in these traits between populations in New Zealand's four major salmon-producing rivers. The New Zealand stocks share a known common genetic heritage, so differences in the different populations provide evidence of evolutionary adaptation to local environments.

To study these differences, families of salmon from two rivers (the Rakaia and Waitaki) have been established at NIWA's Silverstream research facility. If differences between the two populations persist as the fish grow to maturity within a common environment, they can be attributed to genetically controlled traits indicative of evolution.

Currently, the focus of the project is to raise these fish to maturity in three distinct environments: in the wild, in a captive freshwater setting and in cages in a marine setting. This will enable researchers  to differentiate between environmental and genetic effects. This phase of the study, part of which is being conducted with assistance from the salmon farming industry, will continue until 1999.

Results to date show that New Zealand chinook differ in several respects from their present-day cousins in the Sacramento River, and also suggest that there are subtle but persistent differences between the two local populations.

As further data become available over the next four years, the results of JUNIPEX will have implications for salmon management, as well as spin-offs for the New Zealand aquaculture industry. For example, it could help to establish whether the New Zealand salmon fishery should be managed collectively or on a river-by-river basis, and could also help to identify stocks or families best suited for aquaculture.

Martin Unwin, NIWA, Christchurch