Documentation of Annual Spawning Migrations of Anadromous Coregonid Fishes in a Large River using Maturity Indices, Length and Age Analyses, and CPUE
Brown, R.J.; Daum, D.W.; Zuray, S.J.; Carter III, W.K.
Coregonid fishes contribute to major food fisheries throughout the Yukon River drainage in northwest North America. Research and management activities related to these coregonid fishes, however, have been minimal because of the commercial and international focus on Pacific salmon Oncorhynchus spp. populations that share the drainage. We studied five coregonid species at a fishwheel sampling site 1, 200 km from the Bering Sea. They were inconnu Stenodus leucichthys, broad whitefish Coregonus nasus, humpback whitefish C. clupeaformis, least cisco C. sardinella, and Bering cisco C. laurettae. Otolith chemistry studies have shown that anadromy is a common or prevailing life history strategy for all five species at our fish-wheel sampling site. Radio telemetry studies revealed major spawning habitats for four species in the Yukon Flats, an extensive braided region of the river 1, 600 to 1, 700 km upstream from the Bering Sea. The objectives of this study were to document the demographic qualities of migrating coregonids at the fish-wheel sampling site and to define seasonal periods of relative abundance based on daily catch rates. Maturity indices indicated that nearly all fish were mature and preparing to spawn. Minimum lengths and ages of maturity ranged from low values of 23 cm and 2 years for least cisco, to high values of 58 cm and 7 years for inconnu. A video system on the sampling fish wheel provided seven years of species-specific catch rate data that we used to identify the timing of seasonal spawning migrations for all species except least cisco.