Native fish conservation has become a pressing issue for resource managers, often because of threats posed by non-native fish species. Predation and competition for resources can drive native populations extinct, while hybridization reduces the overall genetic integrity of native populations. Fishery restoration projects have been undertaken throughout the United States to conserve threatened and endangered species as well as to rid water bodies of non-native species. These projects use fish toxins (piscicides) to eradicate non-native fish species, and physical barriers to prevent their reinvasion. The use of fish toxicants has been shown to be very effective; however, there are many unknown variables in their use. For example, it is suspected that piscicides change their toxicity with high sunlight exposure, but the intensity and length of sunlight exposure that makes the chemicals ineffective is unknown. It is also recommended that piscicide application stations be closely spaced in low-gradient streams. In this context the terms high and low are relative. Quantifiable descriptions need to be established for these terms. Currently, without more specific piscicide application guidelines, applicators frequently apply too much piscicide in an effort to be cautious and thorough. Over-application of piscicides can be costly and result in high mortality of aquatic invertebrates. Similarly, only vague recommendations exist for applications where sunlight and organic matter could significantly alter the toxicity of piscicides. Once piscicide application instructions are better defined, non-native fish eradication will be more effective. This research team is investigating the toxicants used to eradicate non-native fish to better define piscicide application guidelines.
The goal of this project is to increase the success rate of native fish restoration projects. The research team hopes to increase the efficiency and efficacy of native fish restoration by making piscicide use more efficient and effective. Researchers are carrying out a thorough investigation of the techniques used to eradicate non-native fish, specifically addressing the efficiency of piscicide use.
Specific short-term objectives are to: (1) Determine the relationship between piscicide toxicity and sunlight, turbulence, and organic matter, (2) determine the duration of piscicide toxicity when exposed to characteristics of natural streams, and (3) develop models to predict the probability of target species eradication using piscicides.
Progress to Date:
A series of laboratory studies have been conducted that isolate sunlight, turbulence, and organic matter to determine their individual effect on piscicide toxicity. Results of sunlight experiments provide evidence that piscicides are rapidly detoxified when exposed to direct sunlight. Piscicides applied at concentrations recommended by their manufacturers are ineffective after less than one hour of exposure to direct sunlight. Even if piscicide treated water is shaded from 80 percent of sunlight, exposure to the remaining 20 percent cause the piscicides to be ineffective. Turbulence affects piscicide toxicity less than sunlight. Constant mixing for 24 hours made rotenone and antimycin ineffective.
Stream studies of piscicide toxicity applied rotenone at a single point and used regularly spaced bioassay fish along the stream’s course to determine toxicity. Knowing where along a stream the piscicide became non toxic allowed the research team to measure the stream characteristics that caused that change. Repeating this process on six streams in Montana and Wyoming allowed the researchers to develop a model that identifies common characteristics of streams that cause piscicide detoxification. Large substrates, total dissolved solids, and oxidation-reduction potential are characteristics that are likely causing piscicides to become non-toxic. Measuring these characteristics and applying the predictive model should allow piscicide applicators to predict rotenone persistence.
This project has been changed by removing research on barrier construction and field tests of antimycin. Barriers are an important part of biological restoration of streams but research on barriers and piscicides are significantly divergent. The graduate student and his advisors decided to limit barrier research to the Online Barrier Survey and focus his research on piscicide toxicity. During research on piscicide toxicity the toxicity of the commercially available form of antimycin became unreliable. Small amounts of highly refined antimycin are available from chemical suppliers allowing laboratory research to continue; however, the amount necessary to treat streams is not available. Research on stream application of rotenone will be expanded by comparing two brands of rotenone.
Laboratory experiments will continue in the summer of 2007. The research team will continue exposing piscicides to simulated environmental conditions at the Aquatic Sciences Laboratory at Montana State University. Higher concentrations of piscicides (15 ug/L) will be exposed to simulated environmental characteristics to determine if increasing the concentration can overcome the effects of environmental degradation. The predictive ability of models developed during stream studies of piscicide toxicity will be tested later in the summer of 2007. The researchers will be testing models of piscicide toxicity during ongoing restoration of streams across the western U.S..
Projected Completion Date and Deliverables:
Completion of the overall project is expected in 2009 pending continued funding; reports will be issued accordingly. Publication of research results and presentations at scientific meetings will take place as research is completed.
Critical to this study will be relationships with native-fish managers from several agencies. Relationships with Brad Shepard (Montana Fish Wildlife and Parks), Carter Kruse (Turner Enterprises), Hilda Sexauer (Wyoming Game and Fish Department), Chad Mellison (United States Fish and Wildlife Service), Jim Olsen (Montana Fish Wildlife and Parks), and Todd Koel (Yellowstone National Park) are being developed.