Research Document 2018/029

Population abundance, biological characteristics, and contribution to coastal mixed-stock fisheries of Dolly Varden (Salvelinus malma malma) from the Babbage River: 2010-2014

By Gallagher, C.P., Howland, K.L., Bajno, R., Sandstrom, S.J., and Reist, J.D.

Abstract

Anadromous northern form Dolly Varden (Salvelinus malma malma) from the Babbage River, Yukon Territory was assessed to evaluate population status and determine if the population was sustainably harvested. The methods employed between 2010 and 2014 to collect the information used for the assessment were: a multi-year mark-recapture study to generate abundance estimates, and biological and life history data; a Dual Frequency Identification Sonar (DIDSON) to estimate counts of fish and characterize migration pattern; and coastal harvest monitoring to collect reported harvest information and samples for a genetic mixed-stock fishery analysis to determine the contribution of the Babbage River population to fisheries along the Canadian Beaufort Sea coast. Estimates of abundance from 2010 to 2012 ranged between 5,861  and 6,553  while an estimate of 10,356  was observed in 2013. The total number of fish (regardless of species) enumerated moving in an upstream direction with the DIDSON was 6,531 while the estimated count of Dolly Varden of sizes comparable to those in the mark-recapture study (standardized to ≥365 mm) ranged between 2,839  and 3,119 . Biological information from the mark-recapture study revealed the presence of a wide range of sizes (range= 250-780 mm) that were bimodally distributed between spawning males and females. A high proportion of spawners (40.0-67. 5%) and greater incidences of skip spawning in males and repeat spawning in females was observed. Growth was not only higher in males compared to females but also higher for both sexes in recent years compared to the early 1990s. Genetic mixed-stock fishery analyses revealed that <450 fish from the Babbage River population were harvested annually between 2011 and 2014 along the coast, with the majority of the harvest occurring at Shingle Point. The population experiences an annual harvest rate <6%. Our results indicated the population is currently stable and was sustainably harvested over the period investigated.

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