Utility assessment of otolith microchemistry for salmon fishery management and MP-AES analytical system for food safety in Lake Melville, Labrador

Savoie, Judith (2018) Utility assessment of otolith microchemistry for salmon fishery management and MP-AES analytical system for food safety in Lake Melville, Labrador. Masters thesis, Memorial University of Newfoundland.

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Abstract

Atlantic salmon (Salmo salar) Food, Social, and Ceremonial (FSC) fishery in Lake Melville, Labrador, is an important food source for Indigenous communities living around Lake Melville. The feasibility of using analytical tools to provide information for fishery management and to enable healthcare authorities to ensure food security and safety was assessed in this thesis. First, the feasibility of using otolith elemental concentrations as natural markers of natal river were investigated by using Na, Mg, K, Mn, Zn, Rb, Sr, and Ba concentrations in juvenile and adult salmon. Juvenile salmon were sampled in 11 watersheds flowing into Lake Melville, while adult salmon samples were collected from the FSC fishery. Discrete juvenile otolith elemental composition among watersheds was demonstrated by linear discriminant function analysis, reassigning juveniles accurately to their natal river 89 % (range 73 % - 100 %) of the time on average. Natal river of adults was inferred based on the juvenile dataset. Most of the adult salmon were assigned to the Kenamu River, but the assignment performances seemed to be limited by the interannual and spatial variability of the natal rivers’ chemistry. The results obtained demonstrated that the use of otolith microchemistry as a tool for providing information on natal river for fishery management and ensure food security in Lake Melville is promising but further research is required. Second, the feasibility of using microwave plasma-atomic emission spectrometry (MP-AES) to quantify mercury at low concentrations in Lake Melville salmon muscle tissue was assessed. The method developed was validated by using certified reference material (DORM-3) and by mercury quantification of the salmon tissue performed by an accredited laboratory using cold vapor-atomic fluorescence spectrometry (CV-AFS) and by MP-AES. Mercury concentrations quantified by MP-AES were not significantly different than those obtained by an accredited laboratory, indicating that MP-AES can accurately quantify mercury. The MP-AES limit of detection (0.005 μg g⁻¹ wet weight) is well below the mercury consumption limit (0.2 μg g⁻¹ wet weight) recommended by Health Canada for FSC fisheries. Our results also demonstrated that the Atlantic salmon in Lake Melville are safe to consume (range 0.04 – 0.07 μg g⁻¹ wet weight) and will serve as references for monitoring this fishery after the impoundment of Muskrat Falls. Finally, we concluded that MP-AES is a suitable analytical system for mercury quantification to assess and monitor food safety.

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