Event Title

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 (Seattle, WA : 2018)

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

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

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

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Apr 5th, 2:45 PM Apr 5th, 3:00 PM

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.