Post Stock Monitoring of Hatchery Reared Suckers in Upper Klamath Lake, Oregon

Authors: Josh Gondek, Mckenzie Wasley

Year: 2024

Abstract

Since 2016, the U.S. Fish and Wildlife Service (USFWS) has been rearing wild caught larvae to grow to ~200 mm at the Klamath Falls National Fish Hatchery (KFNFH) captive rearing facility, a priority recovery action listed in C’Waam, or Lost River sucker, Deltistes luxatus, and Koptu, or Shortnose sucker, Chasmistes brevirostrus, recovery plan. This program is known as the Sucker Assisted Rearing Program (SARP), and plans include stocking fish twice-annually in spring and fall, at varying sizes, and at several different locations in Upper Klamath Lake and tributaries. Little data exists for juvenile Lost River and Shortnose sucker because few fish are collected in the wild annually and there is little to no survival of juveniles to recruit into the spawning population. One metric used to inform success of the Sucker Assisted Rearing Program (SARP) and KFNFH repatriation efforts into Upper Klamath Lake is the observation of hatchery reared suckers at spawning grounds detected by various PIT arrays maintained by U.S. Geological Survey (USGS) Klamath Falls Field Station. The first three cohorts of fish released by SARP show a one percent detection at the known spawning grounds with different rearing techniques altering recruitment as condition factor has a large impact on redetection. Larger fish then typically stocked have been released near spawning grounds at time to spawn to help recruitment into the wild adult population, with early results showing fish returning in greater numbers based on age and condition. Considering the age of release at approximately 1.5 years and the age at sexual maturity being 5+ years, there is a multiyear period between time of release and when researchers might begin observing SARP individuals returning to spawning grounds. With the goal to provide insight on the juvenile age class between time of release and detection at spawning grounds, KFNFH initiated supplemental PIT monitoring efforts in summer of 2023. Areas of interest for these additional PIT arrays were informed by heat maps created using data from a concurrent radio telemetry project conducted by the Klamath Falls Fish and Wildlife Office. The radio telemetry project was initiated in spring of 2022 and focuses on hatchery reared suckers. There have been four cohorts of radio tagged SARP fish released into Upper Klamath Lake with tags lasting roughly 1-1.5 years. Primary methods of data collection include active tracking via aerial surveys and passive tracking using remote stations. Understanding how juvenile suckers use Upper Klamath Lake habitat and what rearing techniques improve survival can assist with the recovery of both species in the upper Klamath Basin.