Effect of Low pH on Survival of Brook Trout Embryos and Yolk-Sac Larvae in West Virginia Streams

Abstract

We assessed survival of wild and domestic strains of brook trout Salvelinus fontinalis embryos and yolk-sac larvae in two acidic streams, Little Laurel Run (pH 5.0–5.8) and Little Laurel Creek (pH 4.7–5.4), and a reference stream, Roaring Creek (pH 6.1–7.2), in northern West Virginia from October 1983 to May 1984. Preliminary population surveys suggested that reproductive failure due to low pH had occurred in Little Laurel Run and Little Laurel Creek. Survival rates for all developmental stages, from embryo to yolk-sac larvae, were highest at Roaring Creek and lowest at Little Laurel Creek. Survival was lowest during the hatching period at Little Laurel Run and Little Laurel Creek, where the time to the onset of hatching was less and the hatching and yolk-sac periods were greater than in Roaring Creek. In Little Laurel Run, survival after hatching was lower for the wild strain than for the domestic strain. This may have been due to extension of the hatching period for the wild strain caused by colder water temperatures. In the acidic streams, larval activity and pigmentation were reduced, and incomplete hatching was observed. These effects were most pronounced at Little Laurel Creek. Reduced survival of embryos and yolk-sac larvae may explain the low population density and altered population structure (mostly older, larger fish were present) of brook trout at Little Laurel Run and the absence of a brook trout population at Little Laurel Creek.