An introduction to the use of electronic tagging to provide insights into salmon migration and survival

Abstract

The west coast of North America serves as home for five species of semelparous salmon and the iteroparous steelhead and cutthroat trout, all in the genus Oncorhynchus. Currently, only Chinook salmon (O. tshawytscha) and steelhead trout (O. mykiss) reside in the rivers and streams of California’s Central Valley. By contrast, the coastal streams of California contain coho salmon (O. kisutch), Chinook salmon and, to a much lesser extent, cutthroat trout (O. clarki). The rivers and streams of the Central Valley are unique because they host four Chinook salmon runs identified by the season when most adults return to freshwater to spawn. These seasons include winter, spring, fall, and late-fall (Fry 1961; Stone 1874). Of the four runs, the fall run is the most abundant, largely due to supplementation by hatchery production (Fisher 1994). Fall-run juvenile Chinook salmon emigrate to the ocean soon after hatching. Some of their springrun and winter-run counterparts engage in similar conduct, thereby exhibiting what is known as ocean-type behavior. Late-fall and some spring-run juveniles use a different strategy, remaining in freshwater for a few weeks to several months before outmigrating to the ocean at a larger size. This pattern is described as stream-type behavior. The ocean-type juveniles spend relatively little time in streams and enter the ocean at a small size [80 mm fork length (FL)]. The stream-type juveniles enter the ocean at 120–180 mm FL. These larger stream-type smolts are also called yearlings. Central Valley steelhead are currently recognized only as winter run, although in the past there may have been a summer run as wIell (Needham et al. 1941). Juvenile steelhead vary in freshwater residency and age at ocean entry. While many enter the ocean as smaller sub-yearlings, others enter as larger yearlings or when even older. Populations of coho salmon migrate upstream and spawn in coastal streams and larger rivers outside of the Central Valley, especially in the area north of the Golden Gate, the estuarine exit for Central Valley salmonids. Today salmon populations are only a fraction of their historical abundance, primarily because of the loss of spawning habitat that has resulted from dam construction. Sacramento River winter-run Chinook salmon are classified as endangered under the U.S. Endangered Species Act (ESA) of 1973, with Central Valley steelhead and spring-run Chinook salmon listed Environ Biol Fish (2013) 96:131–133 DOI 10.1007/s10641-012-0099-x