A case study of fine scale habitat use by first ocean year Chinook salmon: implications for growth and predation exposure
Presentation Abstract
Epipelagic habitats occupied by juvenile Chinook Salmon in the Salish Sea are structured at fine scales by tidal currents, wind, and topography. How juvenile salmon distribution interacts with this structure may have implications for diet, growth, and exposure to predation. We have developed two adjacent (~ 4 km apart) sites in the Southern Gulf Islands with differing oceanography as a case study of juvenile Chinook Salmon habitat use in late summer and fall of their first ocean year. We characterized the physical and biological oceanography of these sites with a combination of temperature profiles, zooplankton sampling, and hydroacoustic surveys. Using a flexible, low cost, small vessel based approach (microtrolling), we investigated distribution, diet and growth of juvenile Chinook Salmon between July and October. We also employed acoustic telemetry to directly measure Chinook Salmon movements within and around our study area. Our results suggest that individual juvenile Chinook Salmon, even of the same age and stock, behave differently. Differing patterns of habitat use could be related to trade-offs between growth and predation exposure. Predation and failure to reach a critical size prior to winter are two leading hypotheses to explain depressed marine survival of Salish Sea Chinook Salmon. Our work suggests that fine scale processes should be taken into account when evaluating these hypotheses.
Session Title
The Salish Sea Marine Survival Project: Understanding Salmon Survival
Conference Track
SSE11: Species and Food Webs
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE11-227
Start Date
5-4-2018 2:45 PM
End Date
5-4-2018 3:00 PM
Type of Presentation
Oral
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--Salish Sea (B.C. and Wash.); Fishes--Habitat--Research--Salish Sea (B.C. and Wash.); Fishes--Seasonal distribution--Salish Sea (B.C. and Wash.); Underwater acoustics--Research
Geographic Coverage
Salish Sea (B.C. and 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
A case study of fine scale habitat use by first ocean year Chinook salmon: implications for growth and predation exposure
Epipelagic habitats occupied by juvenile Chinook Salmon in the Salish Sea are structured at fine scales by tidal currents, wind, and topography. How juvenile salmon distribution interacts with this structure may have implications for diet, growth, and exposure to predation. We have developed two adjacent (~ 4 km apart) sites in the Southern Gulf Islands with differing oceanography as a case study of juvenile Chinook Salmon habitat use in late summer and fall of their first ocean year. We characterized the physical and biological oceanography of these sites with a combination of temperature profiles, zooplankton sampling, and hydroacoustic surveys. Using a flexible, low cost, small vessel based approach (microtrolling), we investigated distribution, diet and growth of juvenile Chinook Salmon between July and October. We also employed acoustic telemetry to directly measure Chinook Salmon movements within and around our study area. Our results suggest that individual juvenile Chinook Salmon, even of the same age and stock, behave differently. Differing patterns of habitat use could be related to trade-offs between growth and predation exposure. Predation and failure to reach a critical size prior to winter are two leading hypotheses to explain depressed marine survival of Salish Sea Chinook Salmon. Our work suggests that fine scale processes should be taken into account when evaluating these hypotheses.
