Spawning of the cobia,Rachycentron canadum, in the Chesapeake Bay area, with observations of juvenile specimens

Abstract

Pelagic eggs collected in Atlantic coastal waters adjacent to Chesapeake Bay have been identified as those of the cobia,Rachycentron canadum (Linnaeus). The egg diameters ranged from 1.16 mm to 1.42 mm with a mean of 1.27 mm. The single large oil globule had a mean diameter of 0.38 mm.

The presence of gravid females and the appearance of cobia eggs in plankton collections indicated that spawning occurs between mid June and mid August. Sampling in 1960 showed spawning maxima to be in June and July.

Although virtually all of the cobia eggs were collected in the Atlantic, knowledge of the current patterns in the survey area led to the conclusion that spawning occurred in lower Chesapeake Bay or in the immediate vicinity of the Virginia Capes.

The color pattern and fin shape is described and illustrated from two juvenile cobia collected in August 1962. Observations made before capture of the juveniles point out that certain adult behavioral characteristics are already well established in the first few months of juvenile existence.