The answers is as follows:
A. The Department of Fisheries and Oceans (DFO) 2002 lamprey control field season began on April 22. Up to June 18, DFO had treated 13 streams with a lampricide 3-trifluoromethyl-4-nitrophenol (TFM). The concentrations used varied between 1.0 and 8.0 mg/L and the amount of TFM used ranged between 0.3 kg. and 2342 kg. The total amount of TFM applied was 5845.3 kg. The concentration of TFM required to kill sea lamprey larvae (referred to as the minimum lethal concentration or MLC) is a function of stream pH and alkalinity while the total amount of TFM used depends on the MLC and the size or flow of the stream.
B. The lake trout and other fisheries in the Great Lakes collapsed during the 1950s due to a combination of overfishing and the invasion of sea lamprey (Petromyzon marinus), an exotic species that is native to the Atlantic Ocean and its tributaries. Sea lampreys accessed the Great Lakes following the construction of canal systems and other navigation works. The governments of Canada and the United States signed and enacted the Great Lakes fishery convention treaty in 1956, in response to the collapse of the fishery in the Great Lakes. The convention created the Great Lakes Fishery Commission (GLFC) to undertake fishery research in the Great Lakes and to control populations of sea lamprey. The GLFC conducts an annual program of sea lamprey control in the Great Lakes through its agents, the US Fish and Wildlife Service (USFWS) and DFO. USFWS and DFO assess the population abundance and distribution of lampreys in the lakes and their tributaries. They also conduct a control program that includes, where appropriate the construction of barriers, trapping, and release of sterilized males, to reduce the abundance of spawning lampreys. In addition, a critical component of the control program is the application of a lampricide, TFM, to kill larval lamprey in streams before they migrate to the Great Lakes and begin feeding on fish. If allowed to complete their life cycle, each lamprey can kill the equivalent of 18 kg. of lake trout during the parasitic stage of its life cycle.
DFO uses lampricides as part of an integrated management program to restore and rehabilitate the fishery community of the Great Lakes. The TFM program has been an effective tool in the control of sea lampreys. Sport, commercial, and tribal fisheries in the Great Lakes are now valued at more than $4 billion due in large part to the sea lamprey control program. Applications of TFM in streams are highly effective in killing sea lamprey larvae (~95% mortality) while having minimal effect on other fish species. In 2002 the sea lamprey control program expects that over 10 million larvae will be removed from Great Lakes tributaries.
DFO, USFWS and the GLFC have used TFM since 1958. Recently, the US Environmental Protection Agency and Health Canada have reviewed TFM as part of re-registration legislation in each respective country. TFM is eligible for registration in both countries because it is environmentally benign (breaks down rapidly into non-toxic products) and for the most part, does not significantly affect non-target species. TFM causes mortality in lampreys because their primitive physiology does not have a mechanism to metabolize or excrete TFM while most other species can effectively eliminate TFM in the concentrations that are applied in the control program.
C. The toxicity of TFM is governed by a stream’s alkalinity and pH. Biologists determine the stream pH and alkalinity so that they can apply TFM in concentrations high enough to kill sea lamprey but low enough to not affect non-target fish. Both alkalinity and pH vary through time. However, while alkalinity can vary seasonally, it is relatively stable over the one to three days of a TFM treatment. On the other hand, pH has a daily cycle that is a function of the rate of respiration of periphyton, algae and other aquatic plants. The pH cycle in a stream is generally predictable and repeatable during short (one to two weeks) time intervals. During the day plants extract carbon dioxide from the water and release oxygen. This has the effect of increasing stream pH and reducing the toxicity of TFM. However, during the night, plants use oxygen and release carbon dioxide causing the stream pH to decrease and increasing the toxicity of TFM. The magnitude of the daily changes in stream pH is typically not enough to cause TFM to become toxic to non-target species.
Sudden changes in environmental conditions can change the pH cycle in a stream beyond the typical daily fluctuations. For example, drastic changes in stream water temperature or the amount of sunlight can affect the amplitude of the pH cycle. Several sunny days followed by heavy overcast and a sudden decrease in water temperature can result in a significantly lower night stream pH compared to preceding nights. Other factors can also unexpectedly suppress stream pH. Larger than normal discharges from sewage treatment plants can increase biological oxygen demand, resulting in lower than expected stream pH.
The probability of a TFM treatment causing significant mortality to non-target fish increases if a sudden change in environmental conditions occurs after a TFM treatment begins. In some circumstances, biologists can decrease the volume of TFM being applied and thereby protect non-target fish species. However, in relatively rare instances, especially large pH suppressions can cause some mortality in non-target fish. DFO conducts between 25 and 30 TFM treatments each year. We have observed significant non-target mortality on average once every 10 years, i.e. one in every 250–300 treatments. It should be noted that significant non-target mortality is defined as 50 fish of any particular species and likely constitutes only the most sensitive component of a population.
DFO is investigating the environmental circumstances that occurred in the Credit River after the TFM treatment began. Both a change in solar input and increased biological oxygen demand have been proposed as causes for the sudden decrease in pH in the Credit River.
D. DFO conducts extensive water quality and discharge analyses prior to and following every lampricide application. These tests include monitoring discharge, temperature, pH, alkalinity as well as other water quality parameters. The tests are conducted at pre-determined locations throughout the watershed and are repeated at 30 minute to one-hour (TFM) and two-hour (pH, alkalinity, etc.) intervals. In addition, bioassays are used to confirm that local conditions are consistent with the published relationship between pH, alkalinity and TFM toxicity to larval lamprey and non-target fish. After the initial application of TFM, its concentration, along with water quality parameters, are assessed from the initial application point to the mouth of the river. The concentration of TFM declines to non-detectable levels within hours of completing a treatment.