FISHES OF CHESAPEAKE BAY 
235 
95. Genus RACHYCENTRON Kaup. Crab-eaters 
The characters of the genus are included in the description of the family. A single species of 
wide distribution is known. 
125. Rachycentron canadus (Linnseus). Crab-eater; Cabio; Sergeant fish; “Bonito;” “Black 
bonito.” 
Gasterosteus canadus Linnaeus, Syst. Nat., ed. XII, 1766, p. 491; Carolina. 
Elecate canadus Uhler and Lugger, 1876, ed. I, p. 137; ed. II, p. 117. 
Elacate Canada McDonald, 1882, p. 12; Bean, 1891, p. 91. 
Rachycentron canadus Jordan and Evermann, 1896-1900, p. 948, PI. CXLVIII, fig. 401. 
Head 4; depth 5.45; D. VIII-I, 30; A. I, 23. Body elongate, anteriorly nearly as broad as 
deep, posteriorly compressed; caudal peduncle nearly round, its depth 4 in head; head long and 
broad, depressed; snout broad, 2.95 in head; eye 8.8; interorbital 2.45; mouth large; lower jaw 
projecting; maxillary reaching anterior margin of eye, 2.65 in head; teeth small, pointed, in bands 
on jaws, vomer, palatines, and tongue; gill rakers strong, seven on lower limb of first arch; scales 
minute; lateral line complete; first dorsal composed of very short, stiff spines; second dorsal long, 
elevated anteriorly; caudal fin forked (truncate in young); anal fin similar in shape to the second 
dorsal, but shorter; ventral fins moderate, inserted under base of pectorals, about as long as post- 
orbital part of head; pectoral fins large, 1.15 in head. 
Color of a fresh specimen black above, grayish white to plain below; dorsal and caudal dusky; 
anal and ventrals white with gray or dusky markings; pectorals black. Some specimens observed 
in the Norfolk market were dark brown on back instead of black. 
A single specimen, 810 millimeters (32 inches) in length, weighing 8 pounds when fresh, is 
contained in the present collection, and it forms the basis for the foregoing description. The young 
differ markedly from the adults in the more elongate body, less strongly depressed head, in having 
the caudal fin truncate instead of forked, and in being somewhat lighter in color and having a 
black lateral band, which extends from the snout, through the eye, to the base of the caudal. 
This fish is carnivorous, feeding on fish and crustaceans. Relative to the spawning, Smith 
(1907, p. 221) says: “The fish is known to spawn in Chesapeake Bay in summer, and its eggs 
have been artificially hatched.” Our specimen is a female (captured on May 27, 1922) with ova 
so small that they are not visible to the unaided eye. 
The black bonito is confined to the lower part of Chesapeake Bay, being taken from the York 
River to Cape Charles and Lynnhaven Roads, Va. There are no published statistics of the annual 
catch of this fish. During 1921 about 3,000 pounds, worth $300 to the fishermen, were taken. 
This fish is present in the bay from May until late summer, but it is most common in June. 
Most of the catch is taken with hook and line between the York River and Buckroe Beach, Va. 
On June 21, 1921, at Buckroe Beach, two hand-line fishermen caught four black bonito, weighing 
40, 62, 75, and 84 pounds, respectively; while another boat had three fish, weighing 52, 62, and 82 
pounds, respectively. Hook-and-line fishing appears to be done only in June, but a few fish are 
taken in pound nets throughout the summer. 
The catch is readily disposed of in the markets of Norfolk, Portsmouth, and Phoebus, the 
large fish being cut into steaks. The usual size of the market fish is 10 to 50 pounds, and 84 pounds 
appears to be the largest fish recorded from the bay and the maximum size attained by the species. 
