Overview

Proposed work
Factors affecting early marine survival of juvenile salmon in Puget Sound

Overview

The early marine life of juvenile salmon is a critical period when numerous factors influence immediate or long-term survival of these species. Recent research efforts by a variety of government and tribal agencies have identified localized timing patterns for entry into estuarine and marine waters by various species and stocks of juvenile salmon in Puget Sound. Nearshore habitat utilization by all species decline after mid June (Duffy et al. in press), yet significant catches of juvenile chinook, chum, and other salmon species persist in offshore regions of Puget Sound through at least September (Beamish and Mahnken 1998). Despite the importance of this nearshore-offshore transition and offshore residence period in Puget Sound during summer, little is known about the distribution, feeding, growth, and sources of mortality during and after their nearshore residence in Puget Sound waters. Larger size is associated with higher survival of juvenile salmon both during the growing season and in subsequent life history stages (e.g., overwinter mortality); therefore, how growth performance in Puget Sound influences survival to the adult stage needs to be determined.

Objectives and Approach

Objective 1: Determine whether size-selective mortality significantly influences survival to adulthood for salmon stocks in Puget Sound

Approach: Use scale and otolith analysis of stage-specific size and growth patterns of juveniles compared to the patterns from the same life history stages found on scales/otoliths of the returning adults

Objective 2: Identify life stages when intervals of high mortality (critical mortality periods) occur

Approach: Scale or otolith-based comparisons of stage-specific size frequency distributions for juveniles and surviving adults

Objective 3: Relate critical mortality periods to size and growth patterns associated with different juvenile habitat utilization patterns in Puget Sound

Approach: Otolith microchemistry

Objective 4: Examine the trophic interactions (temporal diet patterns, associated prey availability, and energetic value of key prey) and environmental conditions (i.e., temperature and salinity) that contribute to growth performance during different life history stages within different habitats

Approach: Bioenergetics modeling

Objective 5: Examine temporal offshore distribution, feeding, and size/growth patterns for juvenile salmon in Puget Sound during summer-fall

Approach: Hydroacoustics, purse seining, surface and midwater trawling, acoustic tagging/tracking of larger smolts.

Significance

Salmon populations in Puget Sound are declining. Of particular concern are the wild fall-run chinook salmon, which are believed to have the longest residence in and dependence on the estuarine environment. There is mounting evidence that growth during the early marine residence of most species of anadromous Pacific salmon determines overall marine survival trends. The little that is known about the time that juvenile salmon are in Puget Sound suggests that several salmon species (particularly chinook and chum salmon) may reside extensively in Puget Sound waters and that potential growth conditions may vary both spatially and seasonally. Cutthroat trout and larger salmonids may be significant predators, especially during spring peak outmigration months. In addition, it appears that differences in hatchery practices may be leading to spatial differences in outmigration timing and residence in different areas in the Sound.

Other information

So little is known about the fate of juvenile salmon during their early marine life history, that even the most fundamental information is limited or lacking. Consequently, state management agencies (particularly WDFW), NMFS, and tribal nations in the Puget Sound region are extremely interested in this analysis. This work stimulated a series of coordination and planning sessions among scientists and managers from Washington Department of Fish and Wildlife, NMFS, Army Corps of Engineers, USGS/BRD, King County, City of Seattle, Northwest Indian Fisheries Commission and associated tribes, and Department of Fisheries and Oceans-Canada. Our project demonstrates how comparable data sets can be collected, integrated, and used to evaluate factors limiting survival and growth of juvenile salmon during their early life history in Puget Sound.



Research - Duffy Overview Methods Findings People Pictures Links	Proposed work Factors affecting early marine survival of juvenile salmon in Puget Sound Overview The early marine life of juvenile salmon is a critical period when numerous factors influence immediate or long-term survival of these species. Recent research efforts by a variety of government and tribal agencies have identified localized timing patterns for entry into estuarine and marine waters by various species and stocks of juvenile salmon in Puget Sound. Nearshore habitat utilization by all species decline after mid June (Duffy et al. in press), yet significant catches of juvenile chinook, chum, and other salmon species persist in offshore regions of Puget Sound through at least September (Beamish and Mahnken 1998). Despite the importance of this nearshore-offshore transition and offshore residence period in Puget Sound during summer, little is known about the distribution, feeding, growth, and sources of mortality during and after their nearshore residence in Puget Sound waters. Larger size is associated with higher survival of juvenile salmon both during the growing season and in subsequent life history stages (e.g., overwinter mortality); therefore, how growth performance in Puget Sound influences survival to the adult stage needs to be determined. Objectives and Approach Objective 1: Determine whether size-selective mortality significantly influences survival to adulthood for salmon stocks in Puget Sound Approach: Use scale and otolith analysis of stage-specific size and growth patterns of juveniles compared to the patterns from the same life history stages found on scales/otoliths of the returning adults Objective 2: Identify life stages when intervals of high mortality (critical mortality periods) occur Approach: Scale or otolith-based comparisons of stage-specific size frequency distributions for juveniles and surviving adults Objective 3: Relate critical mortality periods to size and growth patterns associated with different juvenile habitat utilization patterns in Puget Sound Approach: Otolith microchemistry Objective 4: Examine the trophic interactions (temporal diet patterns, associated prey availability, and energetic value of key prey) and environmental conditions (i.e., temperature and salinity) that contribute to growth performance during different life history stages within different habitats Approach: Bioenergetics modeling Objective 5: Examine temporal offshore distribution, feeding, and size/growth patterns for juvenile salmon in Puget Sound during summer-fall Approach: Hydroacoustics, purse seining, surface and midwater trawling, acoustic tagging/tracking of larger smolts. Significance Salmon populations in Puget Sound are declining. Of particular concern are the wild fall-run chinook salmon, which are believed to have the longest residence in and dependence on the estuarine environment. There is mounting evidence that growth during the early marine residence of most species of anadromous Pacific salmon determines overall marine survival trends. The little that is known about the time that juvenile salmon are in Puget Sound suggests that several salmon species (particularly chinook and chum salmon) may reside extensively in Puget Sound waters and that potential growth conditions may vary both spatially and seasonally. Cutthroat trout and larger salmonids may be significant predators, especially during spring peak outmigration months. In addition, it appears that differences in hatchery practices may be leading to spatial differences in outmigration timing and residence in different areas in the Sound. Other information So little is known about the fate of juvenile salmon during their early marine life history, that even the most fundamental information is limited or lacking. Consequently, state management agencies (particularly WDFW), NMFS, and tribal nations in the Puget Sound region are extremely interested in this analysis. This work stimulated a series of coordination and planning sessions among scientists and managers from Washington Department of Fish and Wildlife, NMFS, Army Corps of Engineers, USGS/BRD, King County, City of Seattle, Northwest Indian Fisheries Commission and associated tribes, and Department of Fisheries and Oceans-Canada. Our project demonstrates how comparable data sets can be collected, integrated, and used to evaluate factors limiting survival and growth of juvenile salmon during their early life history in Puget Sound.
Send mail to: ejduffy@u.washington.edu Last modified: 12/12/2004 2:06 PM