Stream Treatments
Depending on the size of a stream system, a treatment can be simple to very complex. A large stream system with many tributaries, beaver impoundments and oxbows can be difficult to treat depending on the distribution of sea lampreys. The time required to complete the preliminary studies and treatment of a stream can vary from one day to two weeks.
Prior to a stream treatment, extensive preparation work in the form of sampling and testing is conducted. The preliminary studies include toxicity tests, water chemistries, and flow measurements. Toxicity tests are conducted to help determine the precise concentration of TFM needed to kill sea lampreys without impact to other aquatic species. The toxicity tests are usually conducted stream side in portable laboratories. Samples for water chemistries are taken from several locations on the river two to four days prior to treatments, and during treatments. Levels of dissolved oxygen, pH, alkalinity, ammonia, and conductivity are measured from the samples. Flow measurements include gaugings which are conducted to determine stream flows at several points in the system. In a complex stream system, dye studies are used to determine the period of time it takes for water to flow between different points. The information from preliminary studies is used to help determine treatment concentrations and times of application of TFM.
During the treatment, certified technicians apply TFM to the river with pumps which are calibrated to adjust the application rate with precision. A Fishery Biologist, chemist or technician collects water samples downstream from the application site and use spectrophotometers to determine the TFM concentration. This analysis is used to determine if the applicator needs to adjust the application rate to maintain the desired concentration of TFM in the stream. Observations and collections are conducted during and after treatments to help determine the effectiveness of the treatment and possible impacts to non-target organisms.
TFM application (circa 1960) Photo by U.S. Fish & Wildlife Service staff
TFM application (circa 1990) Photo by Terry Morse, U.S. Fish & Wildlife Service
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