First Advisor

Steven Courtney

Term of Graduation

Spring 1998

Date of Publication

6-5-1998

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Biology

Language

English

Subjects

Marbled murrelet -- Seasonal distribution -- Washington (State) -- Puget Sound, Marbled murrelet -- Seasonal distribution -- Washington (State) -- Hood Canal

Physical Description

1 online resource (vii, 68 pages)

Abstract

The greater Puget Sound area is home to a diversity of seabirds, however with encroaching human recreational and economic use of these areas these birds are facing unique threats. It is vitally important that we understand where these seabirds occur in order to minimize the risks associated with human influences. Intensive and extensive transects were used to collect data on seasonal distribution and abundance of seabirds, specifically marbled murrelets (Brachyramphus marmoratus), in Puget Sound and Hood Canal. Surveys were conducted from the water during the fall and winter in 1995 and 1996 and summer of 1997. Marbled murrelets were abundant in the Hood Canal study area at all times of the year. In the Skagit/Saratoga study area, murrelets were found only at the north end of Camano Island and off Tulalip Bay with regularity.

Seasonal distribution of marbled murrelets showed several patterns between the two study areas. Murrelets occurred in groups of 2 with the highest frequency in both the Hood Canal and the Skagit/Saratoga study areas. The largest numbers of marbled murrelets occurred at between 250-350 meters offshore. Distribution of marbled murrelets appeared to be correlated with water temperature in August and November in Skagit. A significantly larger number of murrelets occurred in sheltered waters than in exposed waters during the late fall and early winter months (P < 0.001 for 1995, and P < 0.005 for 1996).

Predictability of murrelet occurrence was good in the Skagit/Saratoga study area between years (r2 = 0.7), while predictability of marbled murrelet occurrence was highly variable in Hood Canal between years (r2 = 0.006). Marbled murrelets were positively associated with the presence of western grebes (Aechmophorus occidentalis) and pigeon guillemots (Cepphus columba)in Hood Canal.

These results have implications for fisheries managers in the greater Puget Sound area. Densities of marbled murrelets vary highly in Hood Canal, which makes it difficult to close fisheries in order to reduce the risk of seabird entanglement. These data offer some insights for managers trying to reduce the risk of entanglement of marbled murrelets in Puget Sound and Hood Canal

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/

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Persistent Identifier

https://archives.pdx.edu/ds/psu/44654

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