Effects of explosives on incubating lake trout eggs in the Canadian Arctic

• Main Authors: Welz, M., Faulkner, S.G., Tonn, W.M., Schmitt, D.R.
• Format: Other/Unknown Material
• Language: English
• Published: 2006
• Subjects: envir; geo; Arctic; Lac de Gras; Northwest Territories
• Online Access: https://doi.org/10.7939/R3H708B2P; https://era.library.ualberta.ca/items/ca7a95ab-d801-4470-9c86-952744ae06b6

Industrial development, including geophysical exploration and mining, has increased use of explosives in and near fish habitat. To protect fish and their incubating eggs, Canadian blasting guidelines contain maximum allowable limits for overpressure and peak particle velocity (PPV). Although many studies have focused on how overpressure causes mortality in fish, no studies have examined the effects of PPVs from explosives on fish eggs. We exposed the eggs of lake trout Salvelinus namaycush to blasts from an openpit mine at Lac de Gras, Northwest Territories, and measured the effects on egg mortality. Twenty Plexiglas incubators, each containing 50 eggs, were placed in the lake substrate at four sites; blast-monitoring equipment was also positioned at these sites. Three sites were within 220 m of the pit’s dike, in a zone where PPVs were predicted to exceed the guidelines. A reference site was located outside of this blast zone 2 km away from the pit. Substrate at one of the blast zone sites was composed of material used in dike construction, whereas other sites were natural spawning shoals. To assess egg mortality during the period of greatest egg sensitivity to physical disturbance, half of the incubators were retrieved after 20 d; the remaining incubators were retrieved at ice-out. After 20 d, mortality at two of the three blast zone sites was lower than reference mortality, whereas mortality at the third site did not differ from the reference level. At ice-out, the single blast zone site with nonnatural substrate had higher mortality (by 10%) than the reference site. Ice-out mortality at the other two blast zone sites was similar to that of the reference site. Given that the largest blast exposure (28.5 mm/s) throughout the incubation period was more than double the current maximum allowable limit but still produced mortality similar to the reference level, we suggest that existing guidelines provide ample protection under these blasting conditions. The margin of this protection, however, remains unknown.