Responses of Plasma Electrolytes, Thyroid Hormones, and Gill Histology in Atlantic Salmon ( Salmo salar ) to Acid and Limed River Waters

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Brown, S. B., Evans, R. E., Majewski, H. S., Sangalang, G. B., Klaverkamp, J. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1990
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f90-271; http://www.nrcresearchpress.com/doi/pdf/10.1139/f90-271

Sexually maturing Atlantic salmon, Salmo salar, were held, in the acidic (pH range 4.7–5.2) Westfield River, Nova Scotia and in the nearby, less acidic (pH range 5.2–5.6) Medway River. Exposure to Westfield River water in 1985 (149 d) and 1986 (126 d) reduced plasma osmolality, Na + , Cl − , and Ca ++ (in females only) concentrations of post-spawning fish compared to those in fish held in the Medway River. There were coincidental increases in plasma K + , glucose, and unidentified osmotic fraction (UOF). Gill tissue showed hyperplasia of primary lamellae epithelium. Together, these findings indicate compromised ionoregulatory ability. Decreased plasma T 3 (3,5,3′-triiodo-L-thyronine) suggests altered thyroid function. Westfield River water did not affect plasma T 4 (L-thyroxine) or protein concentrations. An unintentional handling stress caused even more severely depressed plasma ions and more elevated plasma glucose in Westfield fish in 1985 relative to 1986; Medway fish largely recovered from this stress. These observations indicate that acid-exposed fish may be more sensitive to additional stressors. Limestone treatment of Westfield River water (elevating its pH to Medway values) ameliorated ionoregulatory ability but did not affect plasma T 3 and Ca ++ (female). A high salt diet (3% NaCl) failed to protect salmon from the effects of acidic water.