TFM application
Photo by U.S. Fish & Wildlife Service
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 stream two to four days prior to the treatment, and during treatment. Levels of pH, alkalinity, ammonia, and dissolved oxygen are measured from the samples. Measurements are conducted to determine stream flows at many 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 stream using pumps which are adjusted for precise application rates. TFM concentration downstream of the application site is determined by spectrophotometer analysis. 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. The effectiveness of the treatment and possible impacts to non-target organisms is determined by stream observations.
