Effects of Saline Water from North Dakota Lakes on Survival of Fathead Minnow (Pimephales promelas) Embryos and Sac Fry

Eggs and sac fry of the fathead minnow (Pimephales promelas) were subjected in the laboratory to various dilutions of water obtained from four saline North Dakota lakes; three were sodium sulfate-, one a sodium chloride-type lake. In water from the latter, the percent of fertilized eggs surviving as sac fry for 5 days remained the same as the percent hatched: about 90% at treatment levels of 500 – 12,000 μmho and 68% in undiluted lake water of 18,000 μmho. In sodium sulfate-type water, however, about 92% of the fertilized eggs hatched at treatment levels of 500 up to only 6,000 μmho, with about 82% living as sac fry for 5 days in water from two of the lakes, and only about 54% living for 5 days in dilutions made from the most saline lake (lake water of 25,000 μmho). No sac fry survived for 5 days after hatching in sodium sulfate-type water of 12,000 μmho. From laboratory bioassays and field observations, we estimated sodium sulfate-type water exceeding 8,000 μmho during reproductive periods may decrease survival of sac fry.