Acute sensitivity of juvenile shortnose sturgeon to low dissolved oxygen concentrations

There is considerable concern that factors such as eutrophication, industrial pollution, and dredging are adversely affecting the habitats of the endangered shortnose Sturgeon Acipenser brevirostrum. Specific knowledge of the environmental requirements of this species is required if environmental managers are to adequately protect it. We conducted experiments to obtain information on the acute sensitivity of young-of-year shortnose sturgeon to a low dissolved oxygen (DO) concentration. Flow-through tests were conducted with hatchery-produced fish exposed to the ranges of DO, salinity, and temperature expected in the southeastern United States coastal river-estuary interfaces during spring and summer. The estimated concentration lethal to 50% of the test organisms (the LC50 value) after 24 h that we derived for approximately 77-d-old fish tested at 2parts per thousand salinity and a nominal temperature of 25degreesC was 2.7 mg/L (32% saturation). An estimated LC50 of 2.2 mg/L (26% saturation) was obtained for approximately 104-d-old fish tested at 4parts per thousand and 22degreesC. The 24-h, 48-h, and 72-h LC50 values for approximately 134-d-old fish tested at 4.5% and 26degreesC were also 2.2 mg/L (28% saturation). However, the test with approximately 100-d-old fish at 2% and a nominal temperature of 30degreesC yielded a 24-h LC50 of 3.1 mg/L (42% saturation). These data should be of value in derivating DO-protective values for shortnose sturgeon inhabiting estuaries along the Atlantic coast.