DEVELOPMENT, DISTRIBUTION, AND COMPARISON OF RUDDER FISHES 

 Kyphosus sectatrix (Linnaeus) and K. incisor (Cuvier) IN THE WESTERN 

 NORTH ATLANTIC 



By DONALD MOORE, Fishery Research Biologist, 

 Bureau of Commercial Fisheries 



Between January 1953 and December 1954 tlie 

 U.S. Fish and Wildlife Service, in cooperation 

 with the U.S. Navj' Hydrographic Office, the 

 Office of Naval Research, the Georgia Game and 

 Fish Commission, and the Florida State Board of 

 Conservation (through the Marine Laboratory, 

 University of Miami), collected data and samples 

 along the south Atlantic coast of the United States 

 and in the northern Bahama Islands on nine cruises 

 of the motorship Theodore N. Gill (Anderson, 

 Gehringer, and Cohen, 1956 a, b; and Anderson 

 and Gehringer, 1957 a, b; 1958 a, b; 1959 a, b, c). 

 During identification of the specimens collected 

 by dipnet on these cruises, it became apparent 

 that the juveniles of the two species of the genus 

 Kyphosus (family Kj-phosidae) reported from the 

 North Atlantic Ocean were, in many instances, 

 not readily distinguishable from one another. 



Meek and Hildebrand (1925) in their report on 

 the Kyphosus in Panama said, 



* * * The affinities of the Atlantic coast species are, 

 howe\er, not well understood and we cannot be certain of 

 the identification of the specimens at hand. We have 

 compared our specimens with others from North Carolina, 

 Florida, Bermuda, and Cuba. Unless there is much varia- 

 tion among individuals with respect to the depth of body, 

 number of anal and dorsal rays, and number of scales in a 

 lateral series, there must occur on the Atlantic coast more 

 than two species of this genus, the number recognized in 

 current works. * * * A close study of a large amount of 

 material from the Atlantic would be very desirable. 



Later publications do not clarify the identifica- 

 tion of the species of Kyphosus in the North 

 Atlantic; also the development of young of these 

 species has not previously been described. 



This paper presents a review of the taxonomy 

 and the results of a study on the development, 

 distribution, and comparison of the two species 

 of rudder fishes, Kyphosus sectatrix (Linnaeus) 



note:— Approved for publication May 24, 1961. Fishery Bulletin lyu. 



and Kyphosus incisor (Cuvier), found along the 

 Atlantic coast of the United States and the 

 northern Bahamas. 



Young rudder fishes are available as forage for 

 other fish, and adults are considered to be excellent 

 game and food fish. Mowbray (1949) said of 

 K. sectatrix: "Probably the most potentially 

 important small game fish of Bermuda waters is 

 the chub, or rudder fish as it is sometimes known. 

 This fish is found in large numbers amongst the 

 reefs surrounding the island and it rivals the bone- 

 fish in gameness, and surpasses it in strength. 

 The average weight of a chub is about eight pounds 

 though they reach twenty." 



I am grateful for the assistance given bj' various 

 staff members and to those who loaned me speci- 

 mens: Leonard P. Schultz, U.S. National Museum; 

 E. Milbv Burton, Charleston Museum; University 

 of Florida Museum; and David K. Caldwell, 

 Brunswick, Georgia; and for information given by 

 Paulo de Miranda Ribeiro. 



METHODS AND DEFINITIONS 



Measurements of 15 mm. or greater were made 

 with drafting dividers and a Paragon scale; those 

 measurements greater than 50 mm. were recorded 

 to the nearest 0.5 mm. while those from 15 mm. to 

 50 mm. were recorded to the nearest 0.1 mm. 

 Measurements less than 15 mm. were made with 

 a micrometer eyepiece on a stereoscopic micro- 

 scope, and recorded to the nearest 0.1 nun. Draw- 

 ings of fishes, and of caudal osteology, were made 

 with the aid of a camera lucida. 



Original measurements were used in the plots 

 of body proportions to standard length. Unless 

 otherwise stated, specimen lengtiis are standard 

 length measurements. Stained specimens were 

 prepared using the methods described b^' Hollister 

 (1934) and Evans (1948). 



451 



