Dramatic declines in many species of demersal fishes off the West Coast have
resulted in the designation of nine commercially important species as being
overfished. While the causes of those declines are not clearly understood, the
fact remains that a paucity of life history and abundance data exists for many
demersal species, also known as groundfish. Due to this uncertainty, only 21
of the 82 species of groundfish managed under the Groundfish Fishery
Management Plan of the Pacific Fishery Management Council (PFMC) have
been fully assessed. One challenge in designing a systematic survey of
groundfish resources is that many species associate with heterogeneous
substrate of varying relief. In many areas, the rugosity of the substrata
precludes sampling by conventional techniques (e.g. bottom trawl gear). This
has stimulated research that characterizes fish-habitat associations for use in
design of new survey methodology.
Using a combination of remote sensing, in situ observations, and spatial
analytical techniques, four benthic habitat classes were mapped for a large
rocky bank off the central Oregon coast known as Heceta Bank.
Observational data from human-occupied submersible and remotely operated
vehicle dives in the late 1980s, 2000 and 2001 were used to establish habitat
classes with specific substrate characteristics that have been statistically
shown to correlate with demersal fish distributions. The observational habitat
data was then extrapolated over the extent of a multibeam sonar survey
conducted in 1998 using quantitative parameters derived from high-resolution
bathymetric and backscatter imagery of the seafloor. The resultant map
predicts the locations of four habitat classes: Ridge-Gully, High-Relief Rock
(boulders, cobbles), Unconsolidated Sediment 1 (muds), and Unconsolidated
Sediment 2 (sands).
The main utility of the habitat map developed as part of the current study is
that it provides a context for analyses of a variety of spatial data. For instance,
habitat data provides one additional spatial component besides depth and
latitude that can be used to stratify catch per unit effort data from surveys and
commercial logbooks. Also, essential fish habitat for many demersal species
can now be identified in more detail. Finally, habitat data like those presented
here can aid in the design of marine reserves and protected areas by
providing a context for spatial analyses of data of ecological importance. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28885 |
| Date | 08 January 2003 |
| Creators | Whitmire, Curt E. |
| Contributors | Wright, Dawn J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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