Near-Shore Habitat Use by Endangered Juvenile Suckers
in Upper Klamath Lake, Oregon

The Problem

The life histories of endangered Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris in Upper Klamath Lake, Oregon (UKL) have been described, but much of the focus of these descriptions was on adult and larval suckers with less information on

Near-shore habitat with emergent vegetation in Upper Klamath Lake, Oregon.

juveniles. One area of limited knowledge is the habitat requirements for juveniles of both species. Near-shore areas in the lake with emergent vegetation, especially those near the mouth of the Williamson River, have been identified as important habitat for larval suckers (Cooperman and Markle 2000; Oregon State University report to US Geological Survey and US Bureau of Reclamation). There is limited evidence that juvenile suckers use near-shore vegetated habitats (Reiser et al. 2001; report to US Bureau of Indian Affairs), but the extent and timing of use is unknown. Poor water quality in UKL, often associated with massive blooms of the blue-green algae Aphanizomenon flos-aquae, can lead to kills of adult fish. Acutely lethal water quality conditions have been determined for juveniles of both species (Saiki et al. 1999; Environmental Pollution 105:37-44), but it is unknown how chronic exposure to sub-lethal conditions affects the abundance, behavior, and distribution of juvenile suckers.

Objectives

The objectives of this study are 1) to determine how and when juvenile suckers use near-shore habitat with emergent vegetation, 2) determine how the distribution and abundance of juvenile suckers varies between near shore and offshore areas as well as between different areas of the lake over time, 3) determine if water quality conditions affect juvenile sucker abundance and distribution, and 4) determine if there are any species differences in habitat preference, timing of movement, or association with water quality conditions among juvenile suckers.

Methodology

To address our first objective, we will compare the abundance and distribution of juvenile suckers in emergent vegetation and open-water habitats. The most common type of emergent vegetation

Setting a fyke net to sample emergent vegetation.

are Scirpus species (Scirpus), thus we will limit sampling of vegetated sites to those dominated by Scirpus. Sites with appropriate habitat will be identified along shoreline areas near the mouth of the Williamson River. Sampling will be conducted five times a week with overnight sets of pairs of fyke nets, one net sampling Scirpus habitat and the other open water. In addition, we will set net pairs along shoreline without emergent vegetation using protocols described above to determine the relative importance of vegetated habitats in near-shore areas.

To address our second objective we will collect fish once per week along five transects located at sites distributed from the north end to south end of UKL with overnight sets of trap nets. Six nets will be set along each transect at the point nearest shore where water depth was 1 m and at 50, 100, 200, 400, and 600 m from shore. To address our third objective we will collect water quality data hourly with remotely deployed data sondes at three representative sites near the mouth of the Williamson River for the duration of fish sampling. Dissolved oxygen, pH, conductivity, and water temperature will be measured at the deeper of either 1 m off lake bottom or mid water column. Water quality data will also be collected in conjunction with fish sampling along transects. Data sondes will be deployed as at fixed sites to log water quality data at 15-min intervals near nets at 50 and 600 m from shore.

For our final objective, we will sacrifice and preserve a sub-sample of juvenile suckers collected for objectives 1 and 2. Preserved fish will be x-rayed and identified to species with a combination of techniques including vertebral count, lip morphology, and gill raker count. The proportions of each species collected in all sampling will be extrapolated from these results.

Preliminary sampling will be conducted from late June through early July to identify sampling sites and determine when juvenile suckers were large enough to recruit into our nets. Routine sampling will begin mid-July and continue through September.

Highlights and Key Findings

Juvenile sucker captured in emergent vegetation.

Little information exists regarding the role of emergent vegetation for juvenile Lost River and shortnose suckers. Prior to this sampling it was believed by some that juvenile suckers did not utilize shoreline habitats with emergent vegetation. Our sampling has indicated that juvenile suckers do utilize these areas while inundated with water. Information obtained through this study is currently being used by resource managers in the Klamath Basin and will be very important if proposed projects for wetland restoration move forward.

Where Are We Headed In 2003

Work to be completed in FY 2003 will include data entry, proofing and processing of records, and report preparation for the 2002 field season. Work in FY 2003 will also include field season preparation and continued data collection during summer 2003 following methodologies outlined above.

Project Contact

Scott VanderKooi
U.S. Geological Survey
Western Fisheries Research Center
Klamath Falls Field Station
2795 Anderson Ave., Suite 106
Klamath Falls, OR 97603-9365

Email: scott_vanderkooi@usgs.gov
Phone: 541-273-8689 x207
Fax: 541-273-8692

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