Effects of Chronic Exposure to Sublethal pH on Growth, Egg Production, and Ovulation in Brook Trout, Salvelinus fontinalis

Abstract

Hatchery-reared brook trout (Salvelinus fontinalis) were maintained in the laboratory at mean pH values of 7.34, 5.56, 5.16, and 4.48 from early February to early December. At pH 4.48, the mean growth rates of males were uniformly lowered during the entire experimental period. Among females, growth was inhibited during the first 5 mo, but their rate of weight gain recovered during the period of rapid oocyte development. At the end of the experiment, the body weights of both male and female fish in pH 5.16 and 4.48 were only 70.70–77.34% of the control fish at pH 7.34. Growth was not affected by exposure to pH 5.56. Rapid oocyte development occurred simultaneously over all pH groups in June, suggesting that the initiation of gametogenesis was not affected over the range of pH tested, the number of eggs produced was significantly correlated to body weight; consequently the number of eggs produced by the smaller pH 5.16–4.48 females was reduced. Ovulation was also significantly delayed in the acidic groups.