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Observations of handling trauma of Columbia River adult white sturgeon, Acipenser transmontanus Richardson, 1836, to assess spawning sanctuary success

Halvorson, L. J., Cady, B. J., Kappenman, K. M., James, B. W., Webb, M. A. H.
Journal of applied ichthyology 2018 v.34 no.2 pp. 390-397
Acipenser transmontanus, adults, aerial surveys, animal handling, animal stress, boats, fish, fisheries, fishermen, mouth, research projects, space and time, spawning, sport fishing, Columbia River
A sanctuary targeting the time and space occupied by reproductively active white sturgeon, Acipenser transmontanus, during spawning can be an effective method for reducing angling‐related stressors. A catch and release (C&R) fishery targeting over the legal limit (oversize; ≥137 cm fork length) white sturgeon had been intensifying since 1990 and grew in popularity through the 2000s in the lower Columbia River. A research project to describe the reproductive structure of the adult white sturgeon population below Bonneville Dam (rkm 220‐233) was initiated in 2000 and provided the first detailed observations of trauma linked to this C&R fishery. Fish captured from 2003 to 2011 were examined for evidence of in‐season angling damage (hook marks, leaders and lines in buccal cavity) from June through August each year. Carcass surveys were conducted weekly from June through August within a 24.8 km stretch downstream from Bonneville Dam. Catch rates were determined through angler interviews and aerial counts of boat and bank anglers. Four major regulation changes occurred during the course of the study affecting the seasonal spawning sanctuary in space and time. A total of 679 oversize white sturgeon were examined for evidence of in‐season angling damage. The proportion of individuals with evidence of angling, damage indicators per individual, number of carcasses found and the number of carcasses with observed evidence of angling or retained gear, and the total number of oversize fish handled by boat anglers declined after each fishing regulation change. The trends suggest that the sanctuary influenced the number of encounters between anglers and white sturgeon and that increases to the sanctuary in time and space reduced stress endured by oversize white sturgeon.