Sea lamprey control in Lake Champlain

In 1990, the United States Fish and Wildlife Service (USFWS) and state agencies initiated an 8-year experimental sea lamprey (Petromyzon marinus) control program on Lake Champlain to reduce parasitic phase sea lamprey and increase sport fish survival and growth. Twenty-four 3-trifluoromethyl-4-nitrophenol (TFM) treatments were conducted on 13 tributary systems, and nine Bayluscide treatments were conducted on five deltas. Most tributaries received two rounds of treatment, 4 years apart. Trap catches of spawning-phase sea lamprey in three monitored tributaries declined by 80-90% from 1989 to 1997, but nest counts were reduced by only 57% during the same period. Sixteen of 24 TFM treatments reduced ammocoetes to less than 10% of pre-treatment levels. Eight of nine Bayluscide treatments resulted in mean ammocoete mortality rates over 85% in caged test animals. Nontarget effects were noted among amphibians, mollusks, macroinvertebrates, native lamprey, and other fishes, and were higher for Bayluscide treatments than TFM. Recovery of delta taxa occurred within 4 years after treatment. Wounding rates on lake trout and Atlantic salmon were reduced in the Main Lake basin. Catches-per-unit-effort (CPUE) and estimated angler catch of lake trout increased. A moderate (25%), statistically significant increase in survival of 3-4 yr lake trout was noted. Returns of Atlantic salmon (Salmo salar) to tributaries increased significantly after treatment, and there was an estimated 3-fold increase in returns to the Main Lake sport fishery. Angler catches of brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) were higher in 1997 than in 1990. Economic analysis of the program indicated a 3.5:1 economic benefit: cost ratio. Results indicate that the experimental control program was successful, and provide justification for continuing sea lamprey control on Lake Champlain.