CALLINECTES (DECAPODA: PORTUNIDAE) LARVAE IN 

 THE MIDDLE ATLANTIC BIGHT, 1975-77^ 



Peter O. Smyth^ 



ABSTRACT 



Distribution of Callinectes larvae in surface (neuston) and subsurface shelf waters in the Middle 

 Atlantic Bight was determined from quarterly zooplankton collections taken during a 2-year study. 

 Observations confirmed the presence in offshore waters of a large larval pool from which recruitment 

 may take place. Larvae were predominantly late zoeae and megalope, with peak abundances in late 

 summer collections reaching 16,000 per 100 m^ in neuston collections. During summer, crab larvae 

 were distributed across the shelf with the majority at 10-80 km offshore. Abundances were sig- 

 nificantly greater in neuston than subsurface zooplankton collections and generally greater in neuston 

 collections taken at night. Water temperature and distance from shore were factors most closely 

 correlated with abundance of larvae in the neuston. Megalopae of Callinectes were present at outer 

 shelf stations in winter and spring and together with megalopae oi Portunus and other forms were of 

 southern origin. Based on experimentally determined temperature-salinity preferences reported in the 

 literature for Callinectes larvae, metamorphosis may be delayed in cooler offshore waters, thus 

 increasing chances of long-range transport. 



The community of organisms of the surface layer 

 (the neuston^ ) has received increasing attention in 

 terms of samphng problems and possible ecologi- 

 cal significance. Zaitsev ( 1970 ) described the neus- 

 ton as consisting chiefly of early developmental 

 stages of fishes and invertebrates. Berkowitz 

 (1976) and Morris (1975), however, found oceanic 

 neuston faunistically impoverished in comparison 

 with zooplankton of the immediate subsurface. 

 Few studies of the neuston of shelf and shallow 

 waters exist; preliminary indications are that the 

 zooplankton of the surface waters of the continen- 

 tal shelf are at least quantitatively enriched 

 (Grant^). 



Callinectes , euryhaline members of the predom- 

 inantly marine Portunidae, spawn along the shore 

 of open oceans and in mouths of inlets and es- 

 tuaries. Larval development occurs in shelf wa- 



'Contribution No. 952 from the Virginia Institute of Marine 

 Science. From part of a dissertation to be submitted in partial 

 fulfillment of requirements for the degree of Doctor of 

 Philosophy, College of William and Mary. 



^Virginia Institute of Marine Science and School of Marine 

 Science, the College of William and Mary, Gloucester Point, VA 

 23062. 



'Neuston has generally been defined operationally as the 

 community of organisms sampled by gear specifically designed 

 to sample the surface layer. The term is used in that sense in this 

 paper. For a review of numerous terms associated with the sur- 

 face layers, see Banse (1975). 



"Grant, G. C. 1977. Middle Atlantic Bight zooplankton: 

 seasonal bongo and neuston collections along a transect off 

 southern New Jersey. Spec. Rep. Appl. Mar. Sci. Ocean Eng., 

 Va. Inst. Mar. Sci. 173, 138 p. 



Manuscript accepted November 1979. 

 FISHERY BULLETIN; VOL. 78, NO. 2, 1980. 



ters, with probable return inshore by megalopae 

 andjuveniles (Williams 1965, 1971, 1974; Costlow 

 1967; Tagatz 1968). Callinectes megalopae have 

 been reported offshore in shelf waters (Nichols and 

 Keney 1963; Dudley and Judy 1971); retention in 

 shelf waters and subsequent transport of 

 megalopae have been proposed as mechanisms in 

 dispersal, widespread distribution, and mainte- 

 nance of genetic continuity in the species (Costlow 

 1967; Williams 1971, 1974; Cole and Morgan 

 1978). 



Callinectes larvae, at least zoeae, have surface 

 affinities (Tagatz 1968; Dudley and Judy 1971; 

 Sandifer 1972), but megalopae have generally 

 been less numerous in collections than zoeae and 

 limited to bottom samples (Tagatz 1968; Sandifer 

 1972; Goy 1976). Williams (1971), however, re- 

 ported Callinectes megalopae to be active in es- 

 tuarine surface waters at night. 



With the widespread distribution and known 

 abundance of Callinectes adults and the accepted 

 migratory sequence of developmental stages 

 (inshore-offshore-inshore), the reported abun- 

 dance of late stage larvae is surprisingly low. 

 Furthermore, the existence in shelf waters of a 

 Callinectes larval pool from which recruitment to 

 estuaries may occur is based on relatively few 

 studies and limited sampling. 



This paper reports the identification, distribu- 

 tion, and abundance oi Callinectes larvae in neus- 



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