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The Problem Severe water quality problems in Upper Klamath Lake have led to critical fisheries concerns for the region. Upper Klamath Lake was historically eutrophic but has become hypereutrophic presumably due to the draining of surrounding marshes and agricultural practices in the basin (USFWS 1993). As a result, the algal community has shifted to a monoculture of the blue-green algae Aphanizomemon flos-aquae and massive blooms of this species have been directly related to poor water quality episodes in Upper Klamath Lake. The growth and decomposition of dense algal blooms in the lake frequently cause extreme water quality conditions characterized by high pH (9-10.5), widely variable dissolved oxygen (anoxic to supersaturated), and high ammonia concentrations (>0.5 mg/l unionized).
The Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris are endemic to the Upper Klamath Basin of California and Oregon. Declining population trends for both species were noted as early as the mid-1960's, but the severity of the population declines was not evident until the early 1980's. In 1988, the U.S. Fish and Wildlife Service listed both Lost River and shortnose suckers as endangered (Williams 1988). Suspected reasons for their decline included damming of rivers, dredging and draining of marshes, water diversions, hybridization, competition and predation by exotic species, and water quality problems associated with timber harvest, removal of riparian vegetation, livestock grazing, and agricultural practices. Objectives The purpose of this research is to conduct systematic monitoring surveys for Lost River and shortnose suckers in spawning condition at several locations within the Upper Klamath Basin. Both Lost River and shortnose suckers are federally listed endangered species and information on the timing, duration, and extent of spawning is needed to help determine the status of various populations within the basin. The value of a long-term monitoring program will provide data crucial for understanding demographic and reproductive characteristics of these endangered sucker populations. This research will have wide applicability to federal, state, and tribal agencies in the basin for management and recovery efforts. Methodology
The USGS has been conducting field investigations on Lost River and shortnose suckers in Upper Klamath Lake since 1994. The current program conducts monitoring at four general locations in Upper Klamath Lake and its tributaries. Sampling typically begins in mid-February and continues until early June. Sampling methodologies vary by site but in general fish are captured in trammel nets and identified by species and sex, measured, checked for tags (both passive integrated transponder (PIT) and Floy tags), examined for physical afflictions, and examined to determine spawning condition. If suckers do not have a PIT tag, one is inserted to allow for individual identification in future years. In addition to monitoring data, we are sacrificing a limited number of adult suckers to obtain information on age and growth. Highlights and Key Findings The adult sucker monitoring program has provided valuable information on the current status of sucker populations in the Upper Klamath Basin. Abundance indices and and length frequency distributions indicate the current populations are dominated by a few dominant year classes and there has been no significant recruitment into the adult population in the last few years. Continued monitoring will provide further insight into the timing and duration of spawning, sex ratios, size distribution, and species composition of both sucker populations. The status of these population characteristics over time will lead to a better understanding of the spawning populations and stability of both Lost River and shortnose suckers. Where Are We Headed In 2003 Work for 2003 is uncertain due to funding considerations. We hope to continue monitoring efforts as well as continue analyses of existing data sets to improve our understanding of the populations. We are currently analyzing past data to generate reliable estimates of survival, recruitment, and finite rate of population change. Project Contact Rip Shively Email: rip_shively@usgs.gov Publications |
