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Fishery Bulletin 97(3), 1999 



northeastern Gulf waters during early spring. They 

 occur off northwest Florida, Alabama, Mississippi 

 and southeast Louisiana from late-March through 

 October, and return to their wintering grounds in 

 the fall (Franks et al., 1991; Biesiot et al., 1994). 

 Howse et al. (1992) reported that some cobia over- 

 winter in the northern Gulf at depths of 100-125 m. 

 Information on the life history of cobia from the 

 Gulf and U. S. Atlantic coast is limited. Most studies 

 from the Gulf have addressed the occurrence and 

 distribution of early life stages (Dawson, 1971; Ditty 

 and Shaw, 1992), reproductive biology (Biesiot et al., 

 1994; Lotz et al., 1996; Thompson et al.^), and feed- 

 ing (Knapp, 1949, 1951; Miles, 1949; Franks et al., 

 1996; Meyer and Franks, 1996). Hassler and 

 Rainville (1975) collected cobia eggs from the Gulf 

 Stream ofFNorth Carolina, successfully hatched most 

 of them, and reared the larvae through juvenile 

 stages. Mitochondrial DNA analyses of cobia from 

 the northeastern Gulf and U.S. Atlantic coast sug- 

 gest that cobia from those two areas are a unit stock 

 (Hrincevich, 1993). Biesiot et al. (1994) induced 

 spawning in ripe, wild-caught females from the 

 northeastern Gulf, Howse et al. (1975, 1992) de- 

 scribed diseased heart tissues and ubiquitous 

 perivenous smooth muscle cords in viscera of cobia 

 from northern Gulf waters, and Franks (1995) re- 

 ported on an anomalous specimen collected off Mis- 

 sissippi. Only a limited amount of information is 

 available on the age and growth of cobia from the 

 Gulf (Thompson et al.'^; Franks and McBee^) or the 

 U.S. Atlantic coast (Joseph et al., 1964; Richards 

 1967. 1977; Smith, 1995). The objectives of our study 



were to evaluate sectioned sagittal otoliths for age- 

 ing cobia from the northeastern Gulf, construct age- 

 length keys, derive theoretical growth parameters, 

 and obtain length-weight relationships. 



Materials and methods 



We sampled cobia caught by recreational hook-and- 

 line gear in the northeastern Gulf during 1987-95. 

 Cobia were sampled at the dock and at fishing tour- 

 naments. Fish were caught in an area located north 

 of lat. 29°N and between long. 85°20'W and long. 89'W 

 (Fig. 1) in waters that ranged from 2 to 200 m deep. 

 Additional specimens from northwest Florida were 

 provided by the National Marine Fisheries Service 

 (NMFS), and marine enforcement personnel with the 

 NMFS and the Mississippi Department of Marine 

 Resources provided confiscated undersized speci- 

 mens. Owing to the migi-atory nature of cobia, abun- 

 dance varied seasonally. Most fish that we examined 



3 Thompson, B. A.. C. A. Wilson, J. H. Render, and M. 

 Beasley. 1991. Age, growth and reproductive biology of 

 greater amberjack and cobia from Louisiana waters. Year 

 1. Rep. to U. S. Dep. Commer., NOAA, NMFS. Coop. Agree- 

 ment NA90AA-H-MF089, Marine Fisheries Initiative (MARFIN) 

 Prog., Coastal Fish. Inst., Louisiana St. Univ., Baton Rouge, 55 p. 



^ Franks, J. S., and T. M. McBee. 1991. Age and growth. In 

 J. S. Franks, T. D. Mcllwain. R. M. Overstreet. J. T. McBee. J. 

 M. Lotz, and G. Meyer, Investigations of the cobia tRachycentron 

 canadum) in Mississippi marine waters and adjacent Gulf wa- 

 ters. Gulf Coast Res. Lab., Ocean Springs, MS 39564-7000. Fi- 

 nal Rep. to Miss. Dep. Wildl., Fish, and Parks/Bur. Mar Res. (Dep. 

 Mar Res.), 1141 Bayview Ave., Biloxi, MS 39531 and U. S. Fish 

 Wildl. Serv., Atlanta, GA 30345, Proj. No. F-91, p. 1-1 to 1-60. 



94' 00' 



88' 00' 



82° 00' 



TX 



•30° 00' 



26° 00' 



Figure 1 



Map of the Gulf of Mexico showing the northeastern Gulf study area where cobia. Rachycentron canadum. were caught by 

 hook-and-line gear, 1987-95. 



