WENNER AND WENNER: CRUSTACEANS FROM COASTAL HABITATS 



Species Composition 



A total of 60 species of decapod and 3 species of 

 stomatopod crustaceans comprising 59,966 in- 

 dividuals and 11,000 individuals, respectively, was 

 collected during the study (Table 1). Fifteen species 

 accounted for 95% of the total number and 96% of 

 the total biomass: the portunid crabs Portunus 

 gibbesii, P. spinimanns, Ovalipes stephensoni, 0. 

 ocellatu^, Callinectes similis, C. sapidus, and Are- 

 naeus cribrarius; the calappid crab Hepatiis epheli- 

 ticus; the majid crab Libinia emarginata; the 

 penaeid shrimps Penaeus setifertts, P. aztecus, P. 

 duorarum, and Trachypenaeus constrictus; and the 

 sqmllid stomatopods Squilla empusa and S. neglecta. 

 The ranking of these species in terms of numbers 

 of individuals and biomass changed seasonally; how- 

 ever, Portunus gibbesii was the most abundant spe- 

 cies collected during all seasons except spring, when 

 Ovalipes stephensoni dominated catches (Table 1). 

 Previous fauna! surveys in the Carolinian Province 

 have shown that P. gibbesii is a common and abun- 

 dant inhabitant of the coastal zone (Hay and Shore 

 1918; Wass 1955; Rouse 1970). Published informa- 

 tion on 0. stephensoni is limited, but it has previ- 

 ously been reported (as 0. quadulpensis) by Hoese 

 (1973) not to be common in trawl catches off Geor- 

 gia. Biomass of catches was dominated by Calli- 

 nectus sapidus during all seasons except fall when 

 Penaeus setifencs ranked first. Reiser (1976) like- 

 wise noted that C. sapidus comprised a large por- 

 tion by weight of the incidental invertebrate catch 

 of the shrimp fishery off South Carolina. The im- 

 portance of P. setiferu^ in catches during the fall 

 is not unexpected since the species forms the basis 

 of a major commercial fishery in the South Atlan- 

 tic Bight during that time (Reiser 1976, 1977). 



Community, Biomass, and Density 

 Estimates 



Season was an important factor affecting the 

 number of individuals and species collected during 

 the study (Table 2). The median number of indivi- 

 duals was significantly less during winter sampling 

 than at other seasons (x' = 29.83, P < 0.001), while 

 the median number of species was significantly less 

 during winter and spring (x" = 45.60, P < 0.001). 

 Stratified mean catch per tow values also reflected 

 seasonal differences with considerably fewer indivi- 

 duals and lower biomass in catches during winter 

 (Table 3). Similarly, mean total biomass (kg/ha) and 

 density (no. /ha) estimates were lowest for winter. 

 No consistent changes in number of species or num- 



ber of individuals occurred with latitude (Table 2); 

 however, the number of individuals was consistently 

 low at stratum 22 off Cape Canaveral. 



Our results suggest that the community structure 

 of decapod and stomatopod crustaceans from the 

 coastal zone is influenced primarily by seasonality 

 and not latitude. Other investigators have likewise 

 noted the influence of seasonality on the number of 

 motile invertebrate species in inshore habitats. Van 

 Dolah et al. (1984) found that the median number 

 of invertebrate species collected by trawl off the 

 mouth of Winyah Bay, SC was greater in summer 

 than winter. Anderson et al. (1977) collected more 

 species of fishes and invertebrates in the surf zone 

 in summer than any other season, with diversity 

 being least in winter. These results are not surpris- 

 ing since the coastal region of the southwestern 

 Atlantic is prone to great seasonal changes in water 

 temperature. The occurrence of more species, more 

 individuals, and greater biomass in summer may 

 result from more uniform temperatures across the 

 entire shelf allowing intrusion into the coastal zone 

 by middle- and outer-shelf species which represent 

 a northern extension of the tropical Gulf of Mexico 

 and Caribbean fauna (Cerame- Vivas and Grey 1966), 

 as well as offshore movement by euryhaline estu- 

 arine species. The modifying influence of currents, 

 river runoff, and air temperature tend to obscure 

 any latitudinal gradients in community structure. 

 Briggs (1974) considered Cape Canaveral as a zoo- 

 geographic boundary for inner-shelf fauna since 

 many species terminated their range there; how- 

 ever, he hastened to point out that Cape Canaveral 

 is an intermediate point in a lengthy geographic area 

 of change. Depending on water temperature, eury- 

 thermic tropical species can extend far north in the 

 Carolinean Province. During winter under strong 

 northeasterly winds, an inshore zone of cold Virgi- 

 nian coastal current extends south of Cape Hatteras 

 enabling intrusion by northern temperate species 

 (Cerame- Vivas and Grey 1966). Latitudinal trends 

 in community structure are further obscured by 

 using quarterly data to show relationships and the 

 tendency of many species which inhabit the inner 

 shelf on a regular basis to have broad latitudinal 

 ranges. 



The coastal zone along the southeastern United 

 States has previously been reported to contain few 

 species of decapod crustaceans with high abundance 

 (Wenner and Read 1981, 1982). The low number of 

 species in the coastal zone was attributed to the 

 more rigorous and variable hydrographic conditions 

 coupled with a relatively homogeneous substrate 

 compared with other areas of the continental shelf. 



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