Results from radio-telemetry of captively reared desert suckers in Upper Klamath Lake

Authors: Josh Rasmussen, Christie Nichols, Evan Childress

Year: 2022

Abstract

Since 2016, the U.S. Fish and Wildlife Service (USFWS) has been rearing wild caught larvae to grow to ~200 mm in the Klamath Falls National Fish Hatchery and 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. The radio-tagged fish consist of a subset of the stocked fish and will follow the protocols of stocking that are laid out by the SARP program and managers. To determine the fate of the released fish and assist with management of this rearing effort, USFWS has conducted several iterations of radio telemetry and plans to continue tracking released fish. The first effort of radio telemetry of SARP fish occurred in 2018 and 2019. This effort utilized a combination of boat and plane tracking using radio tags that were equipped with a mortality indicator. In 2021, USFWS continued this effort and added additional aerial surveys and lakeside remote stations. Additionally, acoustic tag technology was assessed for use in this system. 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. Given this, information about habitat use by this life stage is lacking, but it is largely assumed that wetland habitat is important for nursery and rearing of these species. This data is some of the first to show an affinity for wetland margin habitat for this life stage. A majority of fish from both stocked fish cohorts were re-detected after being stocked into Upper Klamath Lake. There was no significant difference in survival based on stocking location or size at stocking. However, fish with greater “condition” (heavier than predicted weight at given length) experienced greater survival. Given the ongoing data acquisition of location and survival data, we are gaining a better understanding of rearing management and areas in the lake that need to be protected, restored, and monitored for potential future juvenile recruitment.