Presentation Abstract
The transition of juveniles from fresh water to estuarine and marine environments is a critical period in the life cycle of Pacific salmon, during which survival can be strongly size-selective. Because the amount and quality of food consumed are major determinants of juvenile salmon growth, successful acquisition of energy rich prey during estuarine residence is critical for survival. Humans have likely impacted the feeding relationships of juvenile salmon in estuaries by destroying estuarine wetlands and by altering the abundance of salmon in estuaries. While the estuarine foraging habits of juvenile salmon have been extensively examined, few studies have conducted quantitative comparisons between estuaries that have experienced different levels of human modification. However, comparisons between whole estuaries with different degrees of wetland loss and degradation may be a useful scale of analysis for the diet composition and consumption rates of mobile consumers such as juvenile salmon. To improve our understanding of the effects of wetland loss and conspecific density on juvenile Chinook salmon consumption rate and diet composition in estuaries, we assembled Chinook salmon density and diet data from two Salish Sea estuaries with dramatically different levels of wetland loss and modification. We compared juvenile Chinook salmon diet composition, diet energy density, and instantaneous ration (a proxy for consumption rate) between the two estuaries. We also evaluated the effect of conspecific density on instantaneous ration. We found significant differences in diet composition between juvenile Chinook salmon in the two estuaries, but little difference in instantaneous ration or diet energy density. However, in the highly modified estuary, conspecific density had a significant, negative effect on instantaneous ration, while in the more natural estuary there was little effect on instantaneous ration. These findings suggest that wetland loss may interact with salmon density to constrain the consumption rates of juvenile salmon in estuaries, with resulting consequences for growth and survival.
Session Title
Session S-09D: Salmon Recovery: Implementation and Progress II
Conference Track
Species and Food Webs
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
2-5-2014 10:30 AM
End Date
2-5-2014 12:00 PM
Location
Room 611-612
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Chinook salmon--Food--Washington (State)--Nisqually River Delta; Chinook salmon--Food--Washington (State)--Duwamish River Estuary
Geographic Coverage
Salish Sea (B.C. and Wash.); Duwamish River Estuary (Wash.); Nisqually River Delta (Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Variation in juvenile Chinook salmon diet composition and foraging success between two estuaries with contrasting land-use histories
Room 611-612
The transition of juveniles from fresh water to estuarine and marine environments is a critical period in the life cycle of Pacific salmon, during which survival can be strongly size-selective. Because the amount and quality of food consumed are major determinants of juvenile salmon growth, successful acquisition of energy rich prey during estuarine residence is critical for survival. Humans have likely impacted the feeding relationships of juvenile salmon in estuaries by destroying estuarine wetlands and by altering the abundance of salmon in estuaries. While the estuarine foraging habits of juvenile salmon have been extensively examined, few studies have conducted quantitative comparisons between estuaries that have experienced different levels of human modification. However, comparisons between whole estuaries with different degrees of wetland loss and degradation may be a useful scale of analysis for the diet composition and consumption rates of mobile consumers such as juvenile salmon. To improve our understanding of the effects of wetland loss and conspecific density on juvenile Chinook salmon consumption rate and diet composition in estuaries, we assembled Chinook salmon density and diet data from two Salish Sea estuaries with dramatically different levels of wetland loss and modification. We compared juvenile Chinook salmon diet composition, diet energy density, and instantaneous ration (a proxy for consumption rate) between the two estuaries. We also evaluated the effect of conspecific density on instantaneous ration. We found significant differences in diet composition between juvenile Chinook salmon in the two estuaries, but little difference in instantaneous ration or diet energy density. However, in the highly modified estuary, conspecific density had a significant, negative effect on instantaneous ration, while in the more natural estuary there was little effect on instantaneous ration. These findings suggest that wetland loss may interact with salmon density to constrain the consumption rates of juvenile salmon in estuaries, with resulting consequences for growth and survival.
