Monitoring invasive Northern Pike Esox lucius in Utah Lake

Authors: Ben Wiley, Kurtis Shollenberger, Dale Fonken, Brian Kesner, Paul Marsh

Year: 2022

Abstract

Utah Lake is home to an endemic population of June Sucker Chasmistes liorus. A decline in the June Sucker population led U.S. Fish and Wildlife Service to list the species as endangered in 1986. Extensive recovery efforts by the interagency group “June Sucker Recovery Implementation Program” (JSRIP), led to June Sucker being reclassified from endangered to threatened in 2021. Illegal introduction of Northern Pike Esox lucius into Utah Lake in early to mid-2000s may jeopardize June Sucker recovery. Presence of Northern Pike in Utah Lake was confirmed in sampling by Utah Division of Wildlife Resources (UDWR) in 2011. Because of the substantial threat Northern Pike pose to recovery, it was determined that research and monitoring for Northern Pike in Utah Lake should be initiated to a) identify Northern Pike spawning sites and aggregations; b) identify the best capture methods, and ultimately, control measures; and c) evaluate potential impact of Northern Pike on the June Sucker population. In 2021, a three-year research project was initiated by JSRIP in collaboration with Marsh & Associates and UDWR. This project implements a combination of acoustic and radio tracking, larval trapping, PIT Tag monitoring, and observation to describe Northern Pike movement, habitat use, congregational behavior, and spawning behavior in Utah Lake. Herein, we discuss results and findings from the first ~1.5 years of project work. At time of writing, 13 of 30 tagged Northern Pike in Utah Lake have been contacted by submersible ultrasonic receivers (SURs). These 13 fish account for a total of 10,179 telemetry contacts. SUR data show considerable variation in Northern Pike movement and congregational behavior in different seasonal intervals. Northern Pike movement slowly increases at lake ice-off at the end of winter and culminates in large congregations of Northern Pike entering the lake’s tributaries to spawn during spring when water temperatures exceed 9.0℃. Fish disperse after spawning, but summertime acoustic telemetry and mechanical capture efforts have been unsuccessful at detecting fish so locations and movement patterns during warmer months remain unknown. Home range estimations indicate Northern Pike in Utah Lake exhibit a hybridized foraging behavior by using both littoral habitat and the pelagic zone. Preliminary results suggest early spring months may offer the best time to effectively target and remove significant quantities of Northern Pike from Utah Lake while minimizing bycatch of June Sucker.