Research Document 2021/016

Assessing population dynamics of Arctic Char, Salvelinus alpinus, from the Halokvik and Jayko Rivers, Cambridge Bay, Nunavut, Canada

By Zhu, X., Harris, L., Cahill, C., and Tallman, R.F

Abstract

Arctic Char, Salvelinus alpinus, are frequently exploited in the Halokvik and Jayko rivers by Cambridge Bay fishers for subsistence and commercial purposes. Commercial fisheries for anadromous Arctic Char in the Halokvik River date back to 1968 and at the Jayko River the commercial fishery began in 1975; both have been subjected to periodic closures throughout their history. Harvest data are available for both systems and each has a long-time series of fishery-dependent data. Fishery-independent data are limited for both waterbodies. Through collaboration with the Ekaluktutiak Hunters and Trappers Organization (EHTO), Fisheries and Oceans Canada (DFO) developed the Cambridge Bay Arctic Char Integrated Fisheries Management Plan (IFMP) to promote a common understanding of the “basic rule” for the sustainable management of arctic fisheries. To assess the sustainability of these stocks and to further our understanding of commercial harvest on stock persistence, we applied depletion-based stock reduction analysis (DB-SRA) and other data limited models to assess Arctic Char status and formulate sustainable fisheries management options. Our data indicate that commercial fishery harvests in both rivers underwent significant inter-annual variation. Growth in standard length and round weight of anadromous Arctic Char differed with year, river and sex. Male fish had 16% higher L∞ and 18% lower k values than females in the Halokvik River while male char had 4% higher L∞ and 9% higher k at the Jayko River. In terms of empirical relationships between natural mortality and somatic growth parameters, M was estimated to be 0.1485 ± 0.1272 per year and 0.1758 ± 0.0372 per year at the Halokvik and Jayko rivers, respectively. Using the DB-SRA model, the mean and standard error values of virgin biomass (K) were estimated to be 104.99 ± 0.55 t and 167.15 ± 0.58 t in the Halokvik and Jayko rivers, respectively. Arctic Char in the Halokvik River appeared healthy before 1988 and the population appears to have been overfished since then. Fishing pressure was acceptable until 2004 and the fisheries showed a five-year period of overexploitation during 2005–2010. Currently, the population is still in the overfished state. In the Jayko River, a healthy state was sustained until 1992. Since then, the population has been in an overfished state as F increased. In particular, since 2012, the population has been overfished as the fishery is in a state of moderate overexploitation. Both fisheries have experienced overfishing as determined by the assessment.

Research Document 2021/016 (PDF, 922 KB)

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