The Status Of Stonecats (Noturus Flavus) In The Laplatte And Missisquoi Rivers, Vermont

Stonecats (Noturus flavus, Rafinesque 1818) are designated as a Vermont statelisted endangered species because their known distribution is limited to two systems, the LaPlatte and Missisquoi rivers. The restricted distribution and lack of knowledge on abundance in either river is cause for concern in the continued survival of these populations. Based on the capture numbers and large size range of individuals, we predicted that the population in the LaPlatte River, which provides quality benthic habitat, is stable. However, the Missisquoi River population has the potential for increased intermittent mortalities from two sources, lampricide (3-trifluoromethyl-4nitrophenol) treatment every four years and dewatering during drought conditions. In 2012, 2013, and 2014 we captured, PIT tagged (> 90 mm total length), and VIE marked all Stonecats collected using backpack electrofishing and minnow traps in the LaPlatte and Missisquoi rivers. A total of 1252 were PIT tagged in the LaPlatte River and 125 in the Missisquoi River. First we estimated survival and seniority of Stonecats in the LaPlatte River, using the Pradel model in Program Mark, and derived an average annual lambda of 0.9826. The population estimates from the LaPlatte River were modeled in a population viability analysis (PVA). Few Stonecats were captured in the Missisquoi River, so we used the PVA model to estimate the extinction rates with increased intermittent mortalities on 4-, 6-, and 8-year cycles to predict the long-term viability of the population. With an initial number of 2000 individuals, the population became extinct 100% of the time with an increase in mortality of 0.1 on a 4-year cycle. Our results indicate that the LaPlatte River population is stable, but the Missisquoi River population, in the area affected by lampricide, is not. These results are informative for developing future management scenarios, however, our approach has uncertainty that can only be addressed through obtaining more data on the Missisquoi River population.