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Oregon Plan Overview

Oregon Plan Habitat Surveys
  Site Selection


Oregon Plan Aquatic Habitat Surveys

Habitat Surveys Study Area and Site Selection
Oregon Plan Habitat Surveys are designed to assess all streams within the range of coho salmon.  The target population of streams were contained within watersheds of western Oregon draining into the Pacific Ocean south of the Columbia River.  The area encompassed three Evolutionary Significant Units (ESUís) for coho salmon: the Oregon Coastal ESU, the Lower Columbia River ESU, and the Southern Oregon/Northern California ESU. The Oregon Department of Fish and Wildlife (ODFW) has further divided the Oregon Coastal ESU into three Monitoring Areas (MA) for coho salmon based on studies of genetic variation and life history traits (Kostow 1995).  For fishery management the North Coast MA was further split into a North Coast and a Mid Coast monitoring area (Bodenmiller et al. 1997).  These six monitoring areas are used as the basis for monitoring coho habitat in Oregon coastal streams.

Stream surveys are conducted in the summer season for assessment of status and trends in stream habitat at the monitoring area scale.  In the winter, habitat surveys are conducted to get estimates of habitat status at the population area scale.  More sampling details.

The target populations of streams for the study are based upon a hydrography data layer developed by the USGS at the 1:100,000k scale.  The target populations of streams was updated in 2007 at the 1:24,000k scale.  Streams upstream of large dams that blocked anadromous fish passage were removed from the selection frame.  A random tessellation stratified (RTS) design (Stevens 1997) is used to select potential sample site locations within the population of stream segments.  Stevens and Olsen (1999) described the RTS survey design as applied to the integrated monitoring of habitat, adult spawners, and juvenile salmonids for the ODFW.  The advantage of the RTS selection protocol is the selection of sites spread randomly across the landscape, better representing habitat conditions within a monitoring area and reducing overall sample variance.  In all monitoring areas surveyed, samples are weighted to provide an equal number of sample sites (50).

Some sample sites are not surveyed.  The primary reason for not surveying a site is denial of access from landowners.  Additional sites are dropped because they are too small (<0.6 km2 catchment area), too large (common in the Lower Columbia strata), tidally influenced, or a result of errors in the selection coverage (Table 1).

Survey Methods

Habitat survey

Channel habitat and riparian surveys are conducted as described by Moore et al. (1997) with some modifications.  Modifications to the survey methods included: survey of stream lengths of only 500-1000m and measurement of all habitat unit lengths and widths (as opposed to estimation).  Ten percent of the sites are re-sampled with a separate two-person crew.  Repeat surveys are a randomly selected sub-sample from each geographic area and survey crew.  The repeat surveys are intended to measure within-season habitat variation and differences in estimates between survey crews. 

Fish survey

Fish presence/absence surveys using electrofishing are conducted at habitat sites outside of known coho salmon distribution in all monitoring areas.   A complete description of the methods used is contained in ODFW (1998).  A coordinated but separate project within ODFW conducted coho salmon summer density estimates using snorkeling (Rodgers 2000).

Project Contact:
Matt Strickland
Ron Constable


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