Abundance and Viability of Striped Bass Eggs Spawned in Roanoke River, North Carolina, in 1989

Abstract

Sampling to estimate production and viability of striped bass eggs was conducted at Barnhill’s Landing on the Roanoke River, North Carolina, from 15 April to 15 June 1989. Samples were taken by trailing paired nets at the surface from a small boat for five minutes every four hours for 60 days in the manner established and used by W.W. Hassler since 1959. A total of 4,722 eggs was collected in surface nets: first eggs appeared in samples on 16 April and continued sporadically until 9 June, when the last eggs were collected. Estimated striped bass egg production in the Roanoke River for 1989 was 637,919,162 (S.D. = 27,668,383) eggs. A potential major spawning activity at the end of April was terminated by high and prolonged reservoir discharge, which forestalled peak spawning until the last week in May. Three major spawning peaks were observed: 23-24 May, 26-27 May, and 31 May - 1 June. Seasonal egg production was 50% complete by 26 May, 80% complete by 29 May, and 99% complete by 2 June. Egg viability was estimated as 41.8%, the seventh lowest on record. Major egg deposition ensued when water temperatures reached 18°C. The majority of eggs (76.7%) were less than 10 hours old; an additional 18.5% were between 20 and 28 hours old, and less than five percent were 10 to 18 hours old. Approximately 89% of all eggs was collected at water temperatures between 18 and 21.9°C. Over half of the eggs were collected at water velocities ranging from 100 to 119.9 cm/second; an additional 22% were collected at 60-79,9 cm/second. An inverse relationship between egg viability and water velocity was evident. Less than one percent of all eggs were collected in waters of dissolved oxygen values less than 7.0 mg/L, and 90% of the eggs were in waters with pH values of 7.5 or higher. There was no significant difference in egg catches between surface and oblique collections. Results of this study and others conducted in 1981-1983, and 1988 clearly indicate that reservoir discharge from Roanoke Rapids dam influences striped bass spawning activity in the lower Roanoke River.