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Research Document - 2013/109

Information to support the assessment of Arctic Char (Salvelinus alpinus) in the Sylvia Grinnell River, Nunavut, 2009–2011

By M. VanGerwen-Toyne, C. Lewis, R. Tallman, Z. Martin, and J.-S. Moore

Abstract

From 2009 through 2011, a research program was undertaken on Arctic Char (Salvelinus alpinus) in the Sylvia Grinnell River, Frobisher Bay, Nunavut. The primary objectives were to estimate abundance of the Sylvia Grinnell stock and recommend a sustainable harvest level, but additional information was collected to evaluate stock status (biological characteristics and catch-per-unit effort (CPUE), and proportion the relative removal of Arctic Char caught in the Sylvia Grinnell among various fishing methods (i.e., snagging, angling, gillnets). To better understand the stock structure of Arctic Char in Frobisher Bay, fish movement and genetic stock discrimination analyses were performed on Arctic Char from Sylvia Grinnell River and the nearby Bay of Two Rivers.

A mark-recapture experiment was conducted to determine stock abundance but a reliable estimate could not be calculated due to insufficient data and violation of the Jolly-Seber mark-recapture model assumptions. As such, sustainable harvest was not calculated. However, age frequency data show good recruitment of juveniles, suggesting the stock has the potential to sustain itself under current harvest levels.

Biological and CPUE data were collected from Arctic Char caught in small-mesh gillnets. Fork length of individual fish ranged from 159 mm to 621 mm, with a mean of 350 mm. Age of fish ranged from five to 26 years, with a mean of eight years. The ratio of females to males was 1.37 (58% females) and total instantaneous mortality was 0.44. Daily CPUE varied greatly and was not significantly different annually, but was significantly higher in August compared to July. Comparisons to historic biological and CPUE values for Arctic Char in Sylvia Grinnell were avoided due to differences in gear type used.

Information on the proportion of Arctic Char caught with differing gear types was gathered through voluntary interviews with local fishers and information collected from tag-return forms (completed when a marked fish was recaptured by a local fisher). Reported results suggest that gillnetting was the main method of fish capture and incidents of snagging had declined relative to historic levels. However, the data were limited and contradictory evidence was noted.

Analyses of movement of Arctic Char marked in Sylvia Grinnell River and the Bay of Two Rivers showed limited mixing of stocks in Frobisher Bay, and genetic analyses showed that the two stocks are discreet.

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