Status of Winter Rearing Habitat in Four Coho Population Units_ODFW AQI Winter Report Final 2008

Identification Information

Citation

Originator: ODFW

Publish Date: May 2008

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Jeremy Romer

Job Position: Assistant District Fish Biologist

Telephone: 541-726-3515 X34

E-Mail Address: jeremy.d.romer@odfw.oregon.gov

Description

Abstract: We described the status of habitat in four Oregon coastal coho salmon (Oncorhynchus kisutch) population units (Nehalem, Siuslaw, Coquille, South Umpqua) during winter 2007, estimated the potential winter rearing capacity of streams within those population units, and described the differences observed in stream habitat between winter and summer with emphasis on slow water and secondary channel habitats. Sample sites were randomly selected and spatially balanced within the distribution of coho salmon (juvenile and adult) in Oregon coastal watersheds south of the Columbia River. Twenty five sites were targeted within each of the four population units. Each survey was approximately 1000 m in length and adhered to protocols in Moore et al (2007). The Habitat Limiting Factors Model (HLFM) was used to estimate habitat capacity and quality for rearing juvenile coho. The HLFM predicted that the Nehalem and Siuslaw basins could support the highest density of juvenile coho, and the South Umpqua the least. Seasonal changes in habitat were similar to that reported in a previous study. Winter surveys facilitated the assessment of habitat status and estimating capacity because the surveys were conducted at the time when habitat is most limiting to survival of juvenile coho. Winter surveys were particularly valuable in capturing secondary channel and slow water habitat units such as beaver ponds and alcoves. We also performed a sensitivity analysis to determine the number of survey sites necessary to represent each population unit within the desired confidence range of 30% recommended in the Coho Conservation Plan. Twenty five target sites were not adequate to describe the winter parr capacity within a 95% confidence interval of +30% in each population unit. Confidence intervals of estimates of parr per km ranged from 34 to 60% and mean parr per m2 ranged from 20 to 45%.

Purpose: Objectives for conducting winter habitat surveys in 2007 were 1) complete 25 surveys approximately 1000 m in length in each of four randomly selected Oregon coastal coho salmon (Oncorhynchus kisutch) population units (Nehalem, Siuslaw, Coquille, South Umpqua), 2) describe the status of winter habitat surveyed in 2007 for those population units, 3) estimate the potential winter capacity for juvenile coho in streams within those population units, 4) describe the differences observed in stream habitat between winter and summer with emphasis on slow water and secondary channel habitats, 5) determine the number of survey sites necessary to represent each population unit within the desired confidence recommended in the Conservation Plan, and 6) address the general importance of continued winter survey seasons.

Time Period of Content: Winter 2007

Geographic Extent: Nehalem, Siuslaw, Coquille, South Umpqua River Basins

Status: Final

Use Constraints:

Format: PDF

Data Quality Information

Lineage-Source: Aquatic Inventories Final Winter Report Finalized 2008

Data Information

No data information was supplied.

Entity and Attribute Information

Attributes Description: Field attribute information is available in the attached file(s).

Is a physical copy maintained for reference at Headquarters? Unknown