Abstract. - Age, growth, and 

 mortality of larval Atlantic bumper 

 Chhroscombrus chrysurus were com- 

 pared between cruise samples col- 

 lected during August-September 

 1986 and September 1987 off the 

 Louisiana-Mississippi barrier islands. 

 Calcein-marked Atlantic bumper 

 otoliths (sagitta) were used for age 

 validation. The first growth incre- 

 ment formed on the sagitta approx- 

 imately 2 days after spawning, and 

 daily increments formed thereafter. 

 Length at hatching was estimated at 

 0.7-0.9 mm SL. Growth rates were 

 determined from sagitta and length- 

 frequency data. Highest growth 

 rates occurred in August 1986 (0.40 

 mm/day) and were associated with 

 highest mean temperature and zoo- 

 plankton standing stock estimates. 

 The length exponent for Atlantic 

 bumpers' dry weight-length relation- 

 ship was 3.25. Instantaneous daily 

 mortalities (M) ranged from 0.62 in 

 August 1986 to 0.17 in late Septem- 

 ber 1987. 



Age validation, growtli, 

 and mortality of larval 

 Atlantic bumper (Carangidae: 

 Chloroscombrus chrysurus] in the 

 northern Gulf of Mexico 



Deborah L. Leffler 



Florida Marine Research Institute, Florida Department of Natural Resources 

 3 Jackson Street Fort Walton Beach. Florida 32548 



Richard F. Shaw 



Coastal Fisheries Institute. Center for Wetland Resources 

 Louisiana State University, Baton Rouge, Louisiana 70803-7503 



Manuscript accepted 1 July 1992. 

 Fishery Bulletin, U.S. 90:711-719 (1992). 



Atlantic bumper CMoroscombnis chry- 

 surus, a carangid, is an abundant 

 coastal pelagic fish that is widely 

 distributed in the western Atlantic 

 and Gulf of Mexico (Leak 1977). Ex- 

 ploratory fishing surveys indicate 

 that Atlantic bumper may be abun- 

 dant enough in the northern Gulf of 

 Mexico to harvest commercially (Juhl 

 1966, Bullis and Carpenter 1968, 

 Bullis and Thompson 1970, Klima 

 1971). Presently, Atlantic bumper 

 is mainly a commercial bycatch, 

 marketed primarily for petfood, with 

 little potential as a food fish in the 

 United States (Klima 1971, Leak 

 1977). It, however, may be an impor- 

 tant food source for many predatory 

 fish (Reintjes 1979). 



Atlantic bumper spawn primarily 

 in nearshore coastal waters, espe- 

 cially off Louisiana and Mississippi 

 (Boschung 1957, Perret et al. 1971, 

 Christmas and Waller 1973, Ditty 

 1986, Shaw and Drullinger 1990), 

 and the larvae of this species were 

 most abundant during surveys off the 

 Louisiana-Mississippi (LA-MS) bar- 

 rier islands (Stuck and Perry 1982, 

 Leffler 1989). Larvae have been col- 

 lected from June to October, with 

 abundance peaks usually occurring in 

 July or August (Sabins 1973, Stuck 

 and Perry 1982, Williams 1983, Ditty 

 1986). 



Very little early-life-history work 

 has been conducted on Atlantic 

 bumper (Shaw and Drullinger 1990). 

 Early-life-history information is 

 a critical component in estimating 

 future year-class strength (Gushing 

 1975, Leak and Houde 1987). For ex- 

 ample, slow larval growth rates in- 

 fluence mortality by extending the 

 duration of vulnerable larval stages 

 (Bannister et al. 1974, Houde 1987), 

 while a fast growth rate can possibly 

 increase interaction with predators 

 (Pepin 1991), thereby influencing re- 

 cruitment. Early-life-history data are 

 needed for Atlantic bumper to deter- 

 mine their ecological role and to 

 assist in the prudent development of 

 any directed fishery. 



The abundance of Atlantic bumper 

 over a wide geographic range, their 

 perceived potential as a commercial 

 resource, and their probable eco- 

 logical importance as a forage fish, 

 provided the impetus for conducting 

 this larval age-and-growth study. The 

 goals of this ichthyoplankton study 

 were to (1) validate the periodicity of 

 growth Increments on larval and 

 juvenile Atlantic bumper otoliths, (2) 

 estimate Atlantic bumper length at 

 hatching, (3) estimate the age struc- 

 ture of the sample population, (4) 

 describe larval growth and mortality 

 rates, and (5) relate larval growth 



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