Effects of gill-net trauma, barotrauma, and deep release on postrelease mortality of Lake Trout

Journal of Fish and Wildlife Management
By: , and 



Unaccounted postrelease mortality violates assumptions of many fisheries studies, thereby biasing parameter estimates and reducing efficiency. We evaluated effects of gill-net trauma, barotrauma, and deep-release treatment on postrelease mortality of lake trout Salvelinus namaycush. Lake trout were captured at depths up to 65 m with gill nets in Priest Lake, Idaho, and held in a large enclosure for 10–12 d. Postrelease mortality was the same for surface-release–and deep-release–treated fish (41%). Mixed-effects logistic regression models were used to evaluate effects of intrinsic and environmental factors on the probability of mortality. Presence of gill-net trauma and degree of barotrauma were associated with increased probability of postrelease mortality. Smaller fish were also more likely to suffer postrelease mortality. On average, deep-release treatment did not reduce postrelease mortality, but effectiveness of treatment increased with fish length. Of the environmental factors evaluated, only elapsed time between lifting the first and last anchors of a gill-net gang (i.e., lift time) was significantly related to postrelease mortality. Longer lift times, which may allow ascending lake trout to acclimate to depressurization, were associated with lower postrelease mortality rates. Our study suggests that postrelease mortality may be higher than previously assumed for lake trout because mortality continues after 48 h. In future studies, postrelease mortality could be reduced by increasing gill-net lift times and increasing mesh size used to increase length of fish captured.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Effects of gill-net trauma, barotrauma, and deep release on postrelease mortality of Lake Trout
Series title Journal of Fish and Wildlife Management
DOI 10.3996/122014-JFWM-096
Volume 6
Issue 2
Year Published 2015
Language English
Publisher Scientific Journals
Contributing office(s) Coop Res Unit Seattle
Description 13 p.
First page 265
Last page 277
Country United States
State Idaho
Other Geospatial Priest Lake
Online Only (Y/N) N
Additional Online Files (Y/N) N
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