Simulated Effects of YY-Male Stocking and Manual Suppression for Eradicating Nonnative Brook Trout Populations

Abstract

Eradication of nonnative Brook Trout Salvelinus fontinalis populations is difficult to achieve with standard techniques, such as electrofishing removal or piscicides; new approaches are needed. A novel concept is to stock “supermale” hatchery fish with wild conspecifics. Supermales (M_YY) have two Y-chromosomes, resulting in offspring that are all males; over time, successful supermale reproduction could eradicate the wild population. We constructed an age-structured stochastic model to investigate the effects of manually suppressing wild fish and stocking M_YY fingerlings on the long-term viability of hypothetical nonnative Brook Trout populations. In streams, an annual stocking rate of supermales equivalent to 50% of wild age-0 Brook Trout density combined with an annual selective suppression rate equivalent to 50% of wild Brook Trout density resulted in a time to extirpation of only 2–4 years if supermale fitness was equivalent to wild male fitness. However, time to extirpation in streams was 5–15 years if supermale fitness was 80% lower than wild male fitness. In alpine lakes, higher supermale stocking rates and nonselective gillnetting were required to eradicate Brook Trout populations. If supermales were assumed to be as fit as wild males, however, any supermale stocking rate greater than 49% in alpine lakes or 60% in streams achieved eradication in 10 years or less, regardless of the suppression rate. Because manual suppression and the stocking of M_YY fingerlings can readily be conducted at the levels assumed in our simulations, use of such an integrated pest management (IPM) approach could extirpate undesirable Brook Trout populations within reasonably short periods of time. Given the recent successful development of an M_YY Brook Trout broodstock capable of producing large numbers of M_YY fingerlings and given the positive results of the present simulations for both streams and alpine lakes, field testing of M_YY stocking is warranted within an IPM program that includes manual suppression for eradicating undesirable Brook Trout populations.

Received October 14, 2016; accepted June 10, 2017 Published online August 22, 2017

ACKNOWLEDGMENTS

Liz Mamer assisted with manuscript preparation; thoughtful comments were provided by Robert Carline, Jim Reynolds, and three anonymous reviewers. Funding for this work was provided in part by anglers and boaters through their purchase of Idaho fishing licenses, tags, and permits; and from federal excise taxes on fishing equipment and boat fuel through the Federal Aid in Sport Fish Restoration Program. Use of trade, product, or firm names is for descriptive purposes and does not imply endorsement by the U.S. Government. This article is authorized by the Director of the U.S. Geological Survey.