20 



Fishery Bulletin 91(1), 1993 



recruitment, with small groups of younger larvae of 

 each cohort reaching the estuary earlier, and larger 

 groups of older (and larger) larvae recruited later 

 (Tables 1, 2). The groups are clearly separated by a 

 period of no recruitment, and the separation becomes 

 less evident with later birthweek cohorts. The exist- 

 ence of two groups of recruits from early cohorts could 

 result from dispersion of larvae spawned over the mid- 

 continental shelf at different spawning locations and 

 with different rates of transport to the estuary. 

 Birthweek cohorts after November do not appear to be 

 recruited to the estuary as distinct early and late 

 groups. 



The results show that the abundant larval cohorts 

 of birthweeks 20 and 27 December, caught in January 

 and February in Onslow Bay, contributed substantially 

 to recruitment over the last four weeks in March. 

 Birthweek cohorts of 3, 10, and 17 January were well 

 represented in two later estuarine recruitment peaks. 

 The comparison of birthdate distributions of larvae col- 

 lected in the ocean in January and February and later 

 in the estuary in February and March provided an 

 opportunity to assess the relative survival of cohorts. 

 The Kolmogorov-Smirnov tests showed no significant 

 difference between ocean and estuarine birthdate dis- 

 tributions for larvae spawned over a period (13 

 December-2 January) of intense spawning. Therefore, 

 we conclude that earlier (oceanic) and later (estua- 

 rine) larvae were from the same birthdate distribu- 

 tion, and that survival for the daily cohorts between 

 13 December and 2 January was not age-specific. The 

 lack of seasonal sampling of larvae in the ocean pre- 

 cluded similar comparisons of birthdates throughout 

 the spawning season. 



During their oceanic existence, spot larvae grew rap- 

 idly from a hatching size of about 1.6mmSL to a mean 

 size of 17.2 mmSL at estuarine immigration. The 

 growth curve was sigmoidal and similar to those found 

 by Warlen & Chester (1985) for spot larvae in North 

 Carolina during 1978-79 and 1979-80. Parameter es- 

 timates of the growth model for larval spot in 1987-88 

 in North Carolina, i.e., length at hatching (L (lll =1.156), 

 specific growth rate at hatching (A, o ,=0.074), and the 

 exponential decline of the specific growth rate 

 (°==0.024), were comparable to the growth parameter 

 estimates for 1978-79 and 1979-80 (L, ,=1.686, 1.609; 

 A«,=0.060, 0.067; «=0.021, 0.026) found by Warlen & 

 Chester (1985). Maximum growth rate (9.3 mm, 46 d- 

 old larvae) was between the values that they report 

 (8.0mm, 46d old; and 10.7mm, 45d old). There did 

 not appear to be large differences in within-season 

 growth of spot, although significant differences could 

 be demonstrated. Mean growth was about 0.19- 

 0.21 mm/d for larvae collected during and after the 

 peak immigration period. 



Acknowledgments 



We thank A.J. Chester for statistical assistance and 

 J.J. Govoni, W.F. Hettler, and D.S. Peters for their 

 helpful critical reviews of an early draft of the manu- 

 script. Weekly mean surface-water temperatures for 

 Pivers Island were provided by W.F. Hettler. The se- 

 nior author gives special thanks to Consejo Nacional 

 de Ciencia y Tecnologfa, Direccion General de Asuntos 

 del Personal Academico de la Universidad Nacional 

 autonoma de Mexico, and Fondo para el Desarrollo de 

 los Recursos Humanos del Banco de Mexico, for sup- 

 port of his sabbatical program at the Beaufort Labora- 

 tory of the National Marine Fisheries Service where 

 this paper was developed. 



Citations 



Allen, D.M., & D.L. Barker 



1990 Interannual variations in larval fish recruitment 

 to estuarine epibenthic habitats. Mar. Ecol. Prog. 

 Ser. 63:113-125. 

 Atkinson, L.P. 



1985 Hydrography and nutrients of the southeastern 

 U.S. continental shelf. In Atkinson, L.P., D.W. 

 Menzel, & K.A. Bush (eds.), Oceanography of the 

 southeastern U.S. coastal shelf, p. 77-92. Am. 

 Geophys. Union, Wash. D.C. 

 Beckman, D.W., & J.M. Dean 



1984 The age and growth of young-of-the-year spot, 

 Leiostomus xanthurus Lacepede, in South 

 Carolina. Estuaries 7(4B):487^96. 

 Chao, L.N., & J.A. Musick 



1977 Life history, feeding habits, and functional 



morphology of juvenile sciaenid fishes, in the 



York River estuary, Virginia. Fish. Bull, U.S. 75:657- 



702. 



Checkley, D.M. Jr., S. Raman, G.L. Maillet, & K.M. 



Mason 



1988 Winter storm effects on spawning and larval drift 

 of a pelagic fish. Nature ( Lond. ) 335:346-348. 

 Fahay, M.P. 



1975 An annotated list of larval and juvenile fishes 

 captured with surface-towed meter net in the south 

 Atlantic Bight during four RV Dolphin cruises be- 

 tween May 1967 and February 1968. NOAA Tech. 

 Rep. NMFS SSRF-685, 39 p. 

 Fruge, D.J. 



1977 Larval development and distribution of 

 Micropogonias undulatus and Leiostomus xanthurus 

 and larval distribution of Mugil cephalus and 

 Bregmacerus atlanticus off the southeastern Louisi- 

 ana coast. M.S. thesis, Louisiana State Univ., Baton 

 Rouge, 75 p. 



Fruge, D.J., & F.M. Truesdale 



1978 Comparative larval development of Micropogonias 

 undulatus and Leiostomus xanthurus (Pisces: 



