Growth and Energetic Condition of Dolly Varden Char in Coastal Arctic Waters

Abstract

Dolly Varden char Salvelinus malma are a dominant member of the nearshore Arctic icthyofauna and support one of the largest subsistence fisheries within Arctic coastal communities in Alaska. Despite this importance, numerous aspects of Dolly Varden ecology remain poorly understood, which inhibits efforts to assess the biological consequences of anthropogenic disturbances such as hydrocarbon extraction and climate change within nearshore areas. The goal of this research was to develop and apply new techniques to measure and assess the biological integrity of Dolly Varden populations. To do so, I evaluated the precision of age determination generated from scales, otoliths, and fin rays, developed and validated bioelectrical impedance analysis (BIA) models capable of predicting non-lethal estimates of Dolly Varden proximate content, calculated and correlated retrospective estimates of Dolly Varden growth from archived otolith samples to broad-scale environmental variables, and investigated trends in whole body and tissue proximate content among years and demographics (i.e. reproductive versus non-reproductive individuals). Dolly Varden age determinations can be produced non-lethally using scales for fish up to age 5, while otoliths should be used for fish age 6 and greater. Multi-surface BIA models produced estimates of whole body proximate content with high precision. Retrospective growth analyses indicated growth increased significantly during the early 1980s, and was positively correlated to air temperature, sea surface temperature, and discharge and negatively correlated to ice concentration. Analyses of proximate content suggested that non-reproductive fish contained greater lipid concentrations than reproductive fish. Growth and condition analyses suggest that these metrics vary among years and are a function of reproductive cycles and environmental variability operating at multiple temporal and spatial scales. The adoption of scale-based aging and BIA technology will increase the precision of age-based biological statistics and aid in the detection of change within future Dolly Varden research and monitoring.