Kejimkujik National Park and National Historic Site of Canada
Natural Heritage: Research
Mercury Concentrations in Brook Trout and White Perch
In 1996, a study conducted in Kejimkujik National Park examined mercury levels in fillets of brook trout and white perch. These species are important components of the local recreational fishery. In recent years, mercury concentrations in larger freshwater sportfish, collected from lakes elsewhere in the Maritime Provinces, have been reported to exceed the Health Canada safe consumption guideline.
Researchers sampled brook trout from ten watercourses and collected white perch from three sites. An attempt was made to collect at least ten fish, greater than 20 cm in length, from each location.
The results indicated total mercury concentrations from 0.06 to 1.37 ppm (parts per million) in 81 brook trout averaging 26 cm in length, 264 grams in weight and 3.3 years old. In 30 white perch, the total mercury concentrations ranged from 0.35 to 2.30 ppm for fish averaging 29 cm in length, 399 grams in weight and 9.8 years old. These mercury levels are similar to those observed in others studies in northeastern North America.
It was determined that 15 percent of the brook trout and 93 percent of the white perch fillets in Kejimkujik exceeded the Health Canada safe consumption guideline of 0.5 ppm of mercury.
The results showed that larger, heavier and older fish, in both species, had higher mercury levels. The perch mercury levels were higher than the trout levels because the perch were older and larger.
Mercury levels differed in fish collected from different watercourses.
Mercury uptake by fish is controlled by several factors, including the type of mercury, the diet of the fish, the rate of intake of water through the gills and the chemistry of the water and bottom sediment. While most of the mercury entering the aquatic environment is inorganic, bacteria and other processes convert it to methylmercury. The methylmercury becomes more readily available as it passes through the food chain, accumulating in greater concentrations in fish and other predatory species.
Reference:
d'Entremont, A., J.Carter, N.Burgess, C. Drysdale, G. Brun and S. Beauchamp. 1998. Mercury concentrations in brook trout and white perch from Kejimkujik National Park, Nova Scotia. Parks Canada Technical Reports in Ecosystem Science, Report 018.
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