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Fishery Bulletin 92(2). 1994 



dorsal, and anal fin counts overlap between black 

 driftfish and Atlantic spadefish, but teeth are found 

 in a single band on the dentary in black driftfish 

 (Ginsburg, 1954) and in two bands in Atlantic spa- 

 defish (Hildebrand and Cable, 1938; this study). 

 Dawson's 5.7-7.9 mm specimens had teeth in two 

 bands along the dentary. Because it is unlikely that 

 black driftfish larvae have the same suite of char- 

 acters as Atlantic spadefish, Dawson's specimens 

 should be assigned to Atlantic spadefish. 



Atlantic spadefish spawn from May through Sep- 

 tember based on seasonal abundance of Atlantic 

 spadefish larvae in the northern Gulf; peak spawn- 

 ing occurs between June and August (Ditty et al., 

 1988; this study). Density estimates were highest 

 during June in this study (Table 3), during July in 

 a previous study of coastal waters off central Loui- 

 siana (Ditty, 1986), and during July and August off 

 Mississippi Sound (Stuck and Perry, 1982). Neuston 

 net collections were greatest during August (Table 

 3). Gonad maturity data off South Carolina support 

 peak spawning of Atlantic spadefish during summer 

 (Hayse, 1990). 



Spatial distribution data indicate that Atlantic 

 spadefish larvae are apparently rare in the eastern 

 Gulf. Only one larva was collected east of Mobile 

 Bay (Alabama) during this study, and one larva by 

 Houde et al. 3 in a survey of Gulf waters off Florida. 

 In addition, distribution of both larvae and station 

 depths where larvae were collected indicates that 

 Atlantic spadefish occur primarily in coastal waters 

 (Ditty and Truesdale, 1984; this study), except near 

 the Mississippi River delta where waters may offer 

 additional habitat suitable to larvae because of 

 lower salinities. The relatively high number of posi- 

 tive stations (26%) near the delta during August 

 1988 sampling of frontal zones suggests that fron- 

 tal zones may concentrate larvae. Frontal zone wa- 

 ters may also provide a richer environment for feed- 

 ing and growth of larvae because of higher phy- 

 toplankton and zooplankton biomass (Govoni et al., 

 1989; Grimes and Finucane, 1991). However, Powell 

 et al. (1990) were unable to demonstrate consis- 

 tently that larvae have a nutritional advantage 

 when associated with the Mississippi River plume. 

 A possible association of Atlantic spadefish larvae 

 with riverine frontal areas requires further study. 



In conclusion, understanding the biology, life his- 

 tory, and relations of Atlantic spadefish requires a 

 knowledge of the morphology, distribution, and ecol- 

 ogy of their larvae. Larval characters (e.g. degree of 



3 Houde, E. D., J. C. Leak, C. E. Dowd, S. A. Berkeley, and W. 

 J. Richards. 1979. Ichthyoplankton abundance and diversity 

 in the eastern Gulf of Mexico. Univ. Miami Report BLM Con- 

 tract No. AA550-CT7-28, Miami, FL 33149, 546 p. 



head spination) may also provide insight into the 

 interrelationships among the Ephippidae and their 

 relationship to other families. The potential use of 

 larval characters in defining these relationships, 

 however, cannot be clearly understood until larval 

 development within the family is more fully docu- 

 mented (Watson and Walker, 1992). 



Acknowledgments 



This study was supported by the Marine Fisheries 

 Initiative (MARFIN) Program (contract numbers: 

 NA90AA-H-MF111 and NA90AA-H-MF727). The 

 authors would like to thank the Southeast Area 

 Monitoring and Assessment Program (SEAMAP) 

 and Gulf States Marine Fisheries Commission for 

 providing specimens and environmental data; 

 Churchill Grimes (NMFS, Panama City Lab, 

 Florida) for access to neuston net collections off the 

 Mississippi River delta during August 1988; and 

 John Lamkin (NMFS, Pascagoula, MS) for provid- 

 ing specimens of the reported black driftfish for 

 examination. We also thank Laura Younger for pro- 

 viding scanning electromicrographs of the head 

 spines of Atlantic spadefish larvae. Finally, we thank 

 the reviewers for their comments in substantially 

 improving the manuscript. Jack Javech (NMFS, 

 Miami, FL) illustrated the larvae. 



Literature cited 



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1973. Characters useful to the study of larval 

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 Dawson, C. E. 



1971. Notes on juvenile black driftfish, Hypero- 

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1986. Ichthyoplankton in neritic waters of the 

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1984. Ichthyoplankton surveys of nearshore Gulf 

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1954. Four new fishes and one little known species 

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