Tale of Two Mudpuppy Populations: Impacts of TFM on Ohio’s Second Largest Salamander
Ryan Wagner, MS
Advisor: William E. Peterman
Bycatch is one of the leading threats facing aquatic organisms, worldwide. Pesticide bycatch can occur when nontarget species are incidentally killed during chemical applications that target noxious species. The common mudpuppy (Necturus maculosus) is a declining, river-dwelling salamander that is susceptible to bycatch from 3-trifluoromethyl-4-nitrophenol or TFM applications. TFM is used to control the invasive sea lamprey (Petromyzon marinus) and is responsible for large scale die-offs of common mudpuppies in the Great Lakes region, but the long-term consequences of these die-offs are not well understood. Matson (1990) found a 29% decline in the mudpuppy population in Ohio’s Grand River following a TFM application and predicted that the population could decline by 75% if subjected to four applications in twelve to twenty years. We returned to Matson (1990)’s study site in the Grand River, Ohio to conduct a capture-mark-recapture study to estimate current mudpuppy population size, survival, growth rates, and demographics in 2021 and 2022. To compare results with a mudpuppy population unexposed to TFM, we conducted a mark-recapture study in Alum Creek, Ohio from 2020 to 2023. We used Population Viability Analysis to reveal potential impacts of TFM application on the Grand River population under plausible bycatch scenarios. Following the first year of mark-recapture surveys, federal biologists treated the Grand River with TFM in April 2022. We observed mudpuppy mortality in the Grand River following TFM treatment and detected a possible decline in the estimated population size in 2022. Population size was comparable between the Grand River and Alum Creek, and Grand River mudpuppies appeared to reach sexual maturity at a younger age and attain a smaller adult size. Smaller adults could lead to reduced fecundity, higher predation, or lower competitive ability. Using population viability analyses, we found that the population was likely to decline or become extinct when bycatch impacted more than 5-10% of the population. The population was more sensitive to increased juvenile mortality compared to adult mortality. Our results indicate that TFM bycatch could pose serious risk to nontarget species like mudpuppies if bycatch occurs at the rates tested. Future TFM use and management decisions should be directed with these potential nontarget impacts in mind.