Avoidance behavior of larval sea lampreys in response to Bayluscide® as an evaluation of the utility of a Bayluscide® bar formulation in sea lamprey control operations

Science Center Objects

This study will be conducted to provide information on the avoidance behavior of larval sea lampreys in response to the lampricides 3-trifluoromethyl-4-nitrophenol (TFM) and 2’,5-dichloro-4’-nitrosalicylanilide (niclosamide).  The data generated will be used to evaluate the feasibility of developing a new lampricide formulation (Bayluscide® Solid Bar) for use in the Great Lakes Fishery Commission’s Sea Lamprey Control Program. 



The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has been used to control larval sea lampreys (Petromyzon marinus) in tributaries of the Great Lakes since the late 1950s (Applegate et al. 1961).  In its liquid form, TFM is applied to main tributaries at rates that selectively kill sea lampreys yet minimize the impact on non-target organisms.  Main stream applications of liquid TFM require the use of metering pumps that also require constant monitoring by treatment personnel.  In many of these systems, the number of small stream tributaries to the main channel requiring treatment exceeds the personnel available for liquid applications.  In the early 1980s a solid form, the TFM bar, was developed to be used as a supplemental application to small tributaries as a deterrent to larvae seeking fresh water during treatment of the main system (Gilderhus 1985).  When placed in a stream, the TFM bar slowly dissolves over an 8-10 hour period at a near constant rate thus eliminating the need for metering pumps and continuous monitoring by treatment personnel.  Use of the TFM bar in control operations has its limitations, however.  Some small tributaries can have significant water discharge that require deployment of several bars to achieve the desired TFM concentration.  In addition, tributaries are often isolated with little to no access requiring treatment personnel to hand carry several bars long distances through difficult terrain.  These limitations have prompted treatment managers to seek alternatives.  One such alternative recently proposed is the development of a Bayluscide® bar.  Bayluscide®, the aminoethanol salt formulation of the active ingredient niclosamide (2’,5-dichloro-4’-nitrosalicylanilide), has been used in sea lamprey control operations since 1963 as an additive to TFM as a cost saving measure by reducing the amount of TFM needed to achieve concentrations lethal to sea lamprey.  A 1% addition of niclosamide by weight of TFM will reduce the minimum TFM concentration required for effective sea lamprey control by more than 40% (Gutreuter and Boogaard 2007).  On its own, niclosamide is highly toxic to aquatic life.  The estimated 12 h LC50 for larval sea lampreys in soft water at 17 °C and a pH of 7.5 is 0.12 mg/L (Marking and Hogan 1967).  In contrast, the estimated 12 h LC50 for TFM in the same water is 1.2 mg/L (Marking and Olson 1975).  The current TFM bar formulation has an active ingredient of about 23%.  Preliminary work on a Bayluscide® bar formulation has indicated that the maximum level that can be successfully incorporated into a bar while maintaining an adequate rate of dissolution is about 10% active ingredient niclosamide.  Test trials at greater niclosamide concentrations resulted in inconsistent dissolution, presumably because niclosamide is less soluble in water than TFM.  We estimate that at 10% active ingredient, the Bayluscide® bar would reduce the number of TFM bars needed to repel sea lampreys by more than 4 fold compared to the current total of TFM bars required if avoidance is similar to that of TFM.  One significant drawback of niclosamide, however, is it is not selectively toxic to sea lampreys.  In fact, Dawson et al. (1977) showed that some fish species are more sensitive to niclosamide than larval sea lampreys.  Consequently, the application of Bayluscide® bars to achieve niclosamide concentrations lethal to sea lampreys would likely result in substantial mortalities among non-target organisms.  Concentrations would therefore need to be reduced to minimize negative impacts on non-target organisms. It is unclear, however, if larval sea lampreys would still be repelled at these concentrations.                  

            Previous studies have shown that some fish species can detect and avoid niclosamide. Dawson et al. (1998) noted that Eurasian ruffe (Gymnocephalus cernuus) significantly avoided niclosamide at concentrations typically applied in the field to control larval sea lampreys.  In similar studies, Boogaard et al. (2008, 2016) showed that juvenile lake sturgeon (Acipenser fulvescens) and adult tadpole madtoms (Noturus gyrinus) significantly avoided the granular formulation of Bayluscide® when applied at typical treatment rates.  A successful Bayluscide® bar would need to inhibit larvae from entering smaller tributaries when seeking refuge from the main TFM treatment.  Also, to minimize negative impacts to non-target organisms, niclosamide concentrations resulting from Bayluscide® bar applications must not exceed the LC01 (estimated lethal concentration that produces 1% mortality) for rainbow trout, which has been identified in previous studies as one of the most vulnerable fish species to niclosamide (Marking and Hogan 1967).  In addition, sea lamprey avoidance behavior of niclosamide will require testing in the presence of TFM at treatment levels larvae would encounter in the main channel.




1. Determine the short term (12-h) toxicity of niclosamide (LC01) to rainbow trout in static exposures using Upper Midwest Environmental Sciences Center (UMESC) well water.

2. Evaluate the avoidance behavior of larval sea lampreys to niclosamide concentrations determined in Objective 2.1 (12-h LC01 for rainbow trout) compared to untreated UMESC well water in a two choice preference chamber.

3. Evaluate the avoidance behavior of larval sea lampreys to TFM concentrations at typical treatment levels compared to untreated UMESC well water in a two choice preference chamber.    

4. Evaluate the behavior of larval sea lampreys in the presence of niclosamide concentrations determined in Objective 2.1 (12-h LC01 for rainbow trout) applied to one side and TFM at typical treatment levels applied to the other side of the two choice preference chamber to determine which lampricide has the stronger influence on behavior.