Spear Fishing Spawning Lake Trout; evaluation of an experimental suppression method
Lockard L, Nelson K, Fredenberg W. 2014. Spear Fishing Spawning Lake Trout; evaluation of an experimental suppression method. USFWS Ecological Services, Helena, Montana. Helena, MT
Gillnetting for removal of invasive nonnative lake trout is being conducted in at least a half dozen regional lakes to help conserve native and ESA listed fishes. Gillnetting bycatch can result in loss of important non-target fish, such as bull trout, and gillnetting is also relatively expensive, nonselective, and sometimes causes negative publicity. Purposes of this study were to: 1) observe spawning lake trout behavior underwater, 2) determine the potential efficacy of utilizing spear fishing to selectively remove lake trout from spawning concentrations and 3) evaluate bycatch concerns. Prior to and during an eight week study period, five Scuba divers collectively conducted 104 day and night time dives in Lake McDonald, Glacier National Park. Divers utilizing artificial lights and 6 foot pole spears searched for lake trout along preset depth contours on previously delineated lake trout spawning sites. Lake trout behavioral response to diver disturbance, lights, pursuit, and spearing events was recorded. Spawning concentrations of lake trout were first observed and speared on September 26, 2013 and were consistently present through the end of the evaluation on November 7. During 15 days of diving when lake trout spawning concentrations were present (56 of 78 dives during the study period) over 200 spawning lake trout were observed and divers attempted to spear lake trout a total of 52 times. Of the 52 attempted spearing events, 30 hits and 22 misses were recorded; zero bycatch resulted. Preliminary conclusions reached were: 1) female lake trout size and behavior may make them more vulnerable than males to spearing, 2) spawning lake trout were neither attracted to artificial light nor did they actively avoid lights or diver disturbances, 3) at night, lake trout were most susceptible to spearing partially due to the spotlighting “deer in the headlights” effect, 4) seasonal spear fishing by agency or supervised recreational scuba divers may be a viable management option for suppression of spawning lake trout in delineated spawning areas (< 100’ in depth), and 5.) with basic training, bycatch concerns may be minimal.
- Type
- Unpublished Report
- Authors
- Lockard, Larry; Nelson, Karen; Fredenberg, Wade
- Date of Issue
- 2014-02-10
- Publisher
- USFWS Ecological Services, Helena, Montana
- Units
- GLAC
- Keywords
- Aquatic Studies, Fisheries, Invasive, Non-Native Species, spawning lake trout suppression
- Subjects
- Ecological Framework: Biological Integrity | Invasive Species | Invasive/Exotic animals , Ecological Framework: Biological Integrity | Focal Species or Communities | Fishes