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- Title
Marine survival of steelhead (Oncorhynchus mykiss) enhanced by a seasonally closed estuary.
- Authors
Hayes, Sean A.; Hanson, Chad V.; MacFarlane, R. Bruce; Bond, Morgan H.
- Abstract
To investigate the role that estuaries play in the survival of steelhead, Oncorhynchus mykiss, we compared juvenile size at ocean entry with back-calculated measures of size at ocean entry for returning adults in Scott Creek, a representative California coastal stream. During the annual spring emigration, the largest smolts (>150 mm fork length (FL)) move directly to sea, while some smaller smolts remain in the estuary until sandbar formation creates a closed freshwater lagoon. High growth rates in the estuary throughout the summer result in a near doubling of fork length from the time of estuary entry (mean FL of spring migrants = 102.2 mm; mean FL of fall lagoon resident = 195.9 mm). Analysis of the scale morphology of returning adult steelhead indicates that there is strong size-dependent mortality at sea, with estuary-reared steelhead showing a large survival advantage, comprising between 87% and 95.5% (based on tag returns and scale analysis, respectively) of the returning adult population despite being between 8% and 48% of the annual downstream migrating population. Although the estuary forms less than 5% of the watershed area, it is critical nursery habitat, and steelhead population persistence in southern margin ecosystems may well depend upon healthy estuaries.
- Subjects
RAINBOW trout; ONCORHYNCHUS; STEELHEAD trout; FISH populations; FISHERIES; HABITATS; BIOTIC communities; ESTUARIES; ESTUARINE fishes
- Publication
Canadian Journal of Fisheries & Aquatic Sciences, 2008, Vol 65, Issue 10, p2242
- ISSN
0706-652X
- Publication type
Article
- DOI
10.1139/F08-131