ASSESSING OVERWATER STRUCTURE-RELATED PREDATION RISK ON JUVENILE SALMON: FIELD OBSERVATIONS AND RECOMMENDED PROTOCOLS
The purpose of this study was to evaluate whether conditions associated with overwater structures enhance predation pressure on juvenile salmon in Puget Sound. Washington State Ferry (WSF) terminals served as model overwater structures for exploring these issues. This document reports bird and mammal survey results from six north-central Puget Sound WSF terminals and paired reference sites over both "pre-" and >"peak" periods of outmigrating salmon fry abundance from April 1 to May 10, 2002. The authors conclude that potential salmon predators were slightly more abundant at WSF terminals as compared with unmodified shorelines, although large aggregations were not observed on any occasion. The spatial distribution patterns of both bird and fish predators rarely overlapped with juvenile salmon oriented in surface waters close to shore. The authors were unable to verify whether potential predators were more abundant during peak salmon outmigration, because salmon were available in these habitats throughout the duration of the study. The authors found no evidence that avian, marine mammal, or fish predators consumed more juvenile salmon near WSF terminals than along shorelines without overwater structures. Few species appeared to be targeting abundant fry in nearshore habitats, and the authors observed only two occasions in which predators (one tern sp., one staghorn sculpin) had consumed juvenile salmon. Several hypotheses are offered as to why the authors did not observe elevated rates of predation on juvenile salmon in the face of their greater relative availability to predators in nearshore habitats.
- Record URL:
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Corporate Authors:
Battelle Marine Sciences Laboratory
1529 West Sequim Bay Road
Sequim, WA United States 98382Washington State Department of Transportation
Transportation Building, 310 Maple Park Avenue SE, P.O. Box 47300
Olympia, WA United States 98504-7300Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC United States 20590 -
Authors:
- Williams, G D
- Thom, R M
- Shreffler, D K
- Southard, J A
- O'Rourke, L K
- Sargeant, S L
- Cullinan, V I
- Moursund, R
- Stamey, M
- Publication Date: 2003-9
Language
- English
Media Info
- Features: Appendices; Figures; Photos; References; Tables;
- Pagination: 72 p.
Subject/Index Terms
- TRT Terms: Environmental impacts; Ferries; Habitat (Ecology); Marine terminals; Salmon
- Uncontrolled Terms: Salmon predators
- Geographic Terms: Puget Sound Region
- Subject Areas: Design; Environment; Highways; I20: Design and Planning of Transport Infrastructure;
Filing Info
- Accession Number: 00974813
- Record Type: Publication
- Report/Paper Numbers: WA-RD 573.1,, PNNL-SA-39541,, Final Report
- Contract Numbers: DE-AC06-76RLO 1830
- Files: TRIS, USDOT, STATEDOT
- Created Date: Jun 4 2004 12:00AM