Abundance and Viability of Striped Bass Eggs Spawned in Roanoke River, North Carolina, in 1988

Abstract

Sampling to estimate production and viability of striped bass eggs was conducted at Pollock’s Ferry on the Roanoke River, North Carolina, from 10 April to 7 June 1988. Samples were taken by towing paired nets at the surface for five minutes every four hours for 60 days in the manner established and used by W.W. Hassler since 1959. A total of 20,144 eggs were collected in surface nets: first eggs appeared in samples on 12 April and continued sporadically until 2 June) when the last eggs were collected. Estimated striped bass egg production in the Roanoke River for 1988 was 2,082,130,728. The major portion of eggs was collected in one large peak (11-12 May) arid three minor peaks (15-16 May, 20 May, and 24-25 May). With the exception of 1986, egg production in 1988 was the highest estimate since 1975. Viability for eggs in 1988 was estimated at 89%, the highest estimate since 1972. Primary egg production was observed after water temperatures reached 18 C. The majority (71.8%) of the eggs collected ranged between 20 and 28 hours old. Nearly 13% were between 10 and 18 hours old, and 14% were 30 to 38 hours old. Fewer than one percent were less than 10 hours old. About 79% of the eggs were collected at water temperatures between 18 and 21.9 C; greatest viability was at 20 C and higher. Nearly all eggs (99.5%) were collected at water velocities between 60 and 99.9 cm/ second. Approximately 85% of all eggs were collected in water with dissolved oxygen values ranging between 6.0 and 7.9 mg/L. Only eight percent of the eggs were collected in waters with pH values less than 7.0. Relative steadiness of water discharge from the Roanoke Rapids Dam during spawning season is believed responsible for stable water quality during the period.