Exposure to hexazinone (HEX) and atrazine (ATZ), highly mobile and widely used herbicides along rivers in the United States, is potentially harmful to Atlantic salmon, which have been listed as an endangered species. To determine the effects of these contaminants on smolt development, juvenile Atlantic salmon were exposed under flow-through conditions to 100 μg l−1 HEX, 10 and 100 μg l−1 ATZ in fresh water (FW) for 21 days at 10 °C beginning in mid-April. Twelve fish per treatment were sampled in FW, following a 24 h seawater (SW) challenge and after growth for 3 months in SW. Exposure to 100 μg l−1 HEX or 10 μg l−1 ATZ caused no mortalities of smolts in FW or after SW challenge, while 9% of the fish exposed to 100 μg l−1 ATZ died during exposure. Fish exposed to 100 μg l−1 ATZ reduced feeding after 10 days of exposure and had an impaired growth rate in FW and during the first month in SW; compensatory growth occurred in the second and third month in SW. HEX and ATZ at 10 μg l−1 exposure had no effect on plasma levels of cortisol, growth hormone (GH), insulin growth factor I (IGF-I), thyroxine (T4) and plasma 3,5,3′-triiodo-l-thyronine (T3), Cl−, Mg2+, Na+, Ca2+ in FW or after SW challenge. FW smolts exposed to 100 μg l−1 ATZ had decreased plasma Cl−, Mg2+, Na+ and Ca2+ ions and increased cortisol. No effect on plasma levels of GH, IGF-I, T4 or T3 was found in FW smolts exposed to 100 μg l−1 ATZ. Following SW challenge, fish previously exposed to 100 μg l−1 ATZ had significant increases in hematocrit, plasma cortisol, Cl−, Mg2+, Na+, Ca2+ and a decrease in T4 and T3. It is concluded that under the conditions imposed in this study, HEX does not affect salinity tolerance of Atlantic salmon smolts, while ATZ causes ionoregulatory, growth and endocrine disturbance.
Additional publication details
|Publication Subtype||Journal Article|
|Title||Effects of hexazinone and atrazine on the physiology and endocrinology of smolt development in Atlantic salmon|
|Series title||Aquatic Toxicology|
|Contributing office(s)||Leetown Science Center|
|Google Analytic Metrics||Metrics page|