345 



Abstract.— Dolphinfish, Coryphaena 

 hippurus, ofT Puerto Rico were sampled 

 over an 8-month period to study age and 

 growth from daily increments recorded 

 in the sagittae. A total of 121 otoliths 

 were analyzed. Growth was rapid and 

 nonlinear. No significant differences in 

 growth rate were observed based on 

 sex or on location of capture (north or 

 south coast ). The von Bertalanffy growth 

 parameters were L„ = 1457 mm FL, 

 K = 2.19/yr, and t^ = -0.046 yr. With 

 these values, extrapolated growth over 

 the first year averaged 3.6 mm FIVday. 

 An existing hypothesis of two separate 

 stocks (north and south I in the vicinity 

 of Puerto Rico predicts that fish from 

 the north coast caught primarily in 

 the winter would show a much slower 

 growth rate than fish from the south 

 coast caught primarily in the spring. 

 The absence of growth differences 

 between coasts does not match this pre- 

 diction; however previous growth esti- 

 mates for the northern stock may have 

 been underestimated. On the basis of 

 these results, the stock structure and 

 migration pattern of dolphinfish are 

 likely to be more complicated than orig- 

 inally postulated. 



Age and growth of dolphinfish, 

 Coryphaena hippurus, off Puerto Rico 



Glauco A. Rivera 



Richard S. Appeldoorn 



Department of Marine Sciences 



University of Puerto Rico 



Mayaguez, Puerto Rico 00681-9013 



E-mail address (for R S Appeldoorn, contact auttior) RAppeldoorngrumacuprcluedu 



Manuscript accepted 26 November 1999. 

 Fish. Bull. 98:345-352 (2000). 



The dolphinfish, Coryphaena hip- 

 purus L., is a pelagic and migratory 

 fish, distributed worldwide through- 

 out tropical and subtropical waters 

 (Gibbs and Collette, 1959; Shcher- 

 bachev, 1973). Migrating stocks 

 support important sport and commer- 

 cial fisheries. In the northwestern 

 Atlantic they are fished off North 

 Carolina (Rose and Hassler, 1968), 

 Florida (Beardsley, 1967), in the 

 Gulf of Mexico (Gibbs and Collette, 

 1959), off Puerto Rico (Erdman, 

 1956; Perez and Sadovy, 1996), off 

 the U.S. Virgin Islands and the 

 Windward Islands (Mahon et al., 

 1981), and off Barbados (Oxen- 

 ford and Hunte, 1986). 



Age and growth for dolphinfish 

 have been studied in detail by 

 Beardsley (1967), Rose and Has- 

 sler (1968). Wang (1979), Oxenford 

 and Hunte ( 1983), Uchiyama et al. 

 (1986), and Bentivoglio (1988). No 

 such studies have been conducted 

 for fish off Puerto Rico. For the 

 Caribbean region, the most rele- 

 vant studies are those of Beards- 

 ley (1967), off Miami, and Oxenford 

 and Hunte (1983) in Barbados. 

 Beardsley (1967), using annuli on 

 scales, found dolphinfish distri- 

 buted among five age groups: 379 in 

 group 0, 121 in group I, 9 in group 

 II, 1 in group III, and 1 in group 

 IV. In that study, the mean growth 

 rate in the first year was 1.82 mm 

 SL/day. Oxenford and Hunte ( 1983) 

 assumed daily increment formation 

 in the otolith and obtained a linear 

 growth rate of 4.71 mm SL/day for 



all fish. The rate for adult fish ( ±700 

 mm SL) was 1.43 mm SL/day. Oxen- 

 ford and Hunte's assumption of 

 daily increment formation was vali- 

 dated indirectly by comparing their 

 estimated growth rates to modal 

 progression in length frequency dis- 

 tributions; their study was subse- 

 quently validated directly by Uchi- 

 yama et al. (1986) in a study of 

 Hawaiian dolphinfish. Determina- 

 tion of age from annuli has not been 

 validated and remains subjective. 



Dolphinfish have sexually dimor- 

 phic growth; older male fish show 

 an enlargement of the forehead 

 (Schuck, 1951; Lozano-Cabo, 1961). 

 Oxenford ( 1985 ) and Uchiyama et 

 al. (1986) reported differences in 

 the growth rate in length between 

 sexes, but other studies have 

 reported growth as a combination 

 of both sexes; specifically. Rose and 

 Hassler ( 1968 ) found no differences 

 in length at age between males and 

 females. 



Oxenford and Hunte (1986) pro- 

 posed a migi'ation circuit in the 

 western Central Atlantic for two 

 separate northern and southern 

 stocks (Fig. 1). One stock is located 

 southeast, and the other north- 

 west, of Puerto Rico and the Virgin 

 Islands. Abundance of dolphinfish 

 in Puerto Rico peaks from Novem- 

 ber to January and again (albeit to 

 a lesser degree ) from April to June 

 (Perez and Sadovy, 1996). The U.S. 

 Virgin Islands also has a bimodal 

 distribution in abundance, with a 

 large peak in April-May and small 



