Age, Growth and Fecundity of the Cobia, Rachycentron canadum, from Chesapeake Bay and Adjacent Mid-Atlantic Waters

Abstract

Age, growth, fecundity, and distribution of cobia, Rachycentron canadum, were studied. Data were collected primarily from lower Chesapeake Bay and adjacent mid-Atlantic waters. Age analysis by scale methods, growth estimates by use of Bertalannfyˈs equation, and observations of juvenile cobia indicate rapid growth. Ten age groups were represented in scale collections from 284 fish, 4.2–56.4 inches in fork length. Males and females can mature at two and three years, respectively. Growth equations are: males, Lt = 49(1-e−0.21(t+0.67)), Wt = 59 X (1-e−0.13(t-0.62)); females, Lt = 59(1-e−0.20(t+0.65)), Wt = 120(1-e−0.10(t-0.80)). Fecundity in hundreds of thousands of eggs was evaluated as a function of body weight where fecundity was equal to 0.98 times the weight in pounds minus 6.39. The spawning season, late June through mid-August, was defined through observation of gonadal tissue. A disproportionate sex ratio for areas within Chesapeake Bay was noted, 74:26 and 28:72 males to females, for eastern and western shore areas respectively. A possible relation between spawning and a high ratio of males to females was noted for eastern shore areas.