Plasma electrolytes and gill [Al] were determined and gill morphology and histology were examined in Atlantic salmon (Salmo salar) parr and brook trout (Salvelinus fontinalis) from feral populations in acidic streams of southwest Nova Scotia. Plasma [Na+] and [Cl−] were lowest in fish from streams with the lowest pH levels, but there were no correlations between plasma [Na+] or [Cl−] and exchangeable [Al] in streams for both species. Gill [Al] increased exponentially with increasing exchangeable [Al] in water, but was less than 100 μg/g dry weight in both species. There were no correlations between plasma [Na+] or [Cl−] and gill [Al] for both species, and plasma [Na+] and [Cl−] were ultimately linked to low pH. Scanning electron microscopy of gills showed normal primary and secondary lamellae, with few signs of fusion or hyperplasia, only a slight amount of mucus, regular chloride cell crypts, and epithelial cells with distinct microridges. Histology of gill sections showed few lesions in the primary lamellae but some focal histologic lesions in the secondary lamellae of greater than 50% of fish, regardless of ambient pH or [Al]. The histopathology included hypertrophy of individual epithelial, mucous, and chloride cells, clubbing of tips of secondary lamellae, and localized epithelial hyperplasia. These features were focal and not comparable to the extensive morphological changes or histologic lesions usually attributed to high [Al] at low pH. Dissolved organic carbon concentrations greater than 5 mg/L in the acidic streams apparently afforded protection against Al effects at concentrations of at least 360 μg total Al/L.
A Mi’kmaw Perspective on Advancing Salmon Governance in Nova Scotia, Canada: Setting the Stage for Collaborative Co-Existence
