Lower lethal levels of pH for embryos and alevins of Atlantic salmon, Salmo salar L.

Abstract

Embryos and alevins of Atlantic salmon, Salmo salar L., at various stages of development were subjected to several levels of low pH ranging from 4.3 to 2.7, for maximum exposures of 10 000 min in static bioassays at 5 or 6 °C, after incubation from fertilization at pH 6.9–6.6 and 5.0–6.7 °C. Sensitivity of the embryos and alevins to pH stress was dependent on the stage of development. Embryos in early cleavage were more sensitive to low pH than older encapsulated embryos. Alevins were more sensitive to low pH than embryos. The lower lethal limit for embryos during early cleavage was about pH 3.6, while for older embryos in two sequential stages just before hatch it was about pH 3.0 and pH 3.1, successively. Alevins subjected to low pH levels at 7 days and at 28 days after median hatch had a lower lethal limit of about pH 4.0.