Biology and population characteristics of the shortnose sturgeon, Acipenser brevirostrum LeSueur 1818 (Osteichthyes:Acipenseridae), in the Saint John River Estuary, New Brunswick, Canada

Abstract

During a 4-year study, 4178 shortnose sturgeon were captured and 2453 marked with numbered tags and released. For adults, Z was estimated as 0.12–0.15 and F was estimated as 0.01. The population weight–length relationship was log W = 3.21 (log FL) − 5.45, where W = weight in kilograms and FL = fork length in cm. The oldest female was 67 years; the oldest male was 32 years. Von Bertalanffy growth parameters L_∞, W_∞, and K were 127.0 cm, 24.8 kg, and 0.047 for females, and 108.7 cm, 13.9 kg, and 0.063 for males. Sex ratio of adults was 2:1 for females. Males spawned first about age 12 and probably at 2-year intervals thereafter; females spawned at 18 years and 3- to 5-year intervals thereafter. Fecundity was 27 000 – 208 000 eggs per female. Spawning occurs in freshwater, riverine sections of the upper estuary during May–June at 10–15 °C. Feeding occurred only during May to October in fresh water but continued all year in saline water. Juveniles ate mainly insects and crustaceans; adults ate small molluscs. Juveniles remained in fresh water until they attained 45 cm, then joined the regular annual migration of adults, which moved upstream in spring–summer and seaward in fall. Many ripening females migrated upstream in fall and overwintered in deep, freshwater sites adjacent to spawning grounds. The Seber-Jolly estimate of the adult (> 50 cm) population was 18 000 ± 30%.