Acute Toxicity of the Lampricides TFM and Niclosamide to Three Species of Unionid Mussels

摘要

The sea lamprey (Petromyzon marinus), a jawless parasitic eel-like fish native to the Atlantic Ocean (fig. 1), was accidentally introduced into the Great Lakes in the early 20th century through the construction of shipping canals. A member of the Petromyzonidae family, the primitive parasite has been identified as a major cause of the collapse of the Great Lakes fishery in the 1940s and 1950s. The lampricides 3 trifluoromethyl 4 nitrophenol (TFM) and 2 5 dichloro 4 nitrosalicylanilide (niclosamide) have been used to control larval sea lampreys in tributaries of the Great Lakes since the early 1960s. The lampricide TFM is the main compound used to keep sea lamprey populations in check while niclosamide is used primarily in combination with TFM as a cost- saving measure. The addition of niclosamide at a ratio of 1% to TFM will reduce the amount of TFM required for effective treatment by about 40%. Concern has been expressed in recent years over the risk of lampricide applications to nontarget fauna. Of particular concern are several fish, mussel, amphibian, and other rare aquatic species listed as threatened, endangered, or of special concern by state and Federal agencies. As part of a long standing commitment to the Great Lakes Fishery Commission, Ann Arbor, Michigan, scientists at the Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, conduct toxicological risk assessments of the lampricides to nontarget species of interest. Freshwater mussels are an important part of the aquatic community in many waters, often comprising a significant portion of the benthic biomass. In the past century, the diversity and abundance of freshwater mussels have dramatically declined. Freshwater mussels are now recognized as one of the most imperiled faunal groups in North America. Little information exists on the relative toxicity of the lampricides to unionid mussels.