Life history and spawning movements of broad whitefish in the middle Yukon River

Abstract

"Broad whitefish Coregonus nasus have long been an important subsistence resource across its Arctic and sub-Arctic range. Despite its regional importance, little is known about the life history and ecology of this species. This research illuminates fundamental life-history information through the use of catch-per-unit-effort (CPUE) run timing, gonadosomatic index (GSI), radio telemetry, and aging and microchemical analysis of otoliths. From 2001 to 2006, fishwheels were used to capture individuals 1,200 km upstream from the mouth of the Yukon River. CPUE data indicated a consistent increase in daily fish numbers through mid-September. The GSI showed an increasing gonad weight over the sampling period, indicating preparation for spawning. Thirty-one of 41 radio-tagged fish were tracked to a 260 km long spawning area centered 350 km upstream of the tagging site. Thirteen of 17 fish found in the spawning area in 2003 overwintered nearby. Ages of 79 individuals ranged from 5 to 16 years (mean age = 10; median age = 9). Microchemical analysis showed amphidromy in 10 of 12 individuals by examining otolith strontium (Sr) concentrations. This information indicates that the broad whitefish captured in this study were mature, migrating to a spawning/overwintering area, and have a complex amphidromous life history"--Leaf iii