DISTRIBUTION, ABUNDANCE, REPRODUCTION, FOOD HABITS, 

 AGE, AND GROWTH OF ROUND SCAD, DECAPTERUS PUNCTATUS, 



IN THE SOUTH ATLANTIC BIGHT' 



L. Stanton Hales, Jr.^ 



ABSTRACT 



Five years of bottom trawling indicated that round scad were abundant and widely distributed throughout 

 the South Atlantic Bight in summer and fall, but less abundant and restricted to deeper (28-110 m), warmer 

 (>15°C) waters in winter and spring. Adults and juveniles were spatially segregated, with adults 

 dominating catches in inner and outer shelf regions and juveniles dominating midshelf regions year round. 

 Catches over sponge-coral habitat were significantly greater than catches over sand bottom in winter, 

 whereas catches over the two bottom types were similar in other seasons. This seasonal change in distribu- 

 tion may relate to higher productivity and temperature stability of live bottom habitats. Stomach con- 

 tents indicated that round scad are diurnally feeding zooplanktivores; diets changed seasonally and 

 increased in prey diversity with growth. Round scad spavra repeatedly from March through September. 

 Daily growth analysis revealed that both sexes mature in 4-5 months at approximately 1 1 cm fork length. 

 The life span of round scad could not be determined because the growth record of otoliths of most adults 

 was irregular. 



Fishes of the genus Decaptertcs occur in most neritic 

 and some oceanic waters of tropical, subtropical, and 

 temperate latitudes. Little is known of the biology 

 of most species, except for those species which sup- 

 port fisheries in the Hawaiian Islands, the Philip- 

 pines, Japan, and the west coast of Africa (Yama- 

 guchi 1953; Tiews et al. 1970; Akaoka 1971; Boely 

 et al. 1973). Although the taxonomy of Indo-Pacific 

 species is unclear (Berry 1968), three species are 

 recognized in the western North Atlantic: the red- 

 tail scad, Decapte7tis tabl Berry; the mackerel scad, 

 D. macarellus (Cuvier); and the round scad, D. punc- 

 tatus (Agassiz). 



The round scad occurs in the western Atlantic 

 from Nova Scotia to Rio de Janeiro, Brazil, and 

 throughout the West Indies and Bermuda (Berry 

 1968); however, little information is available con- 

 cerning its basic biology. The distribution of the 

 species has been determined from purse seine 

 catches in the Gulf of Mexico (Klima 1971), where 

 it supports a bait fishery, and from bottom trawl 

 catches over sand bottom habitat in the South Atlan- 

 tic Bight (Wenner et al. 1979a, b, c, d, 1980). The 

 location and duration of the spawning season has 



'Contribution No. 71 from the Marine Resources Research In- 

 stitute and No. 222 from the Grice Marine Biological Laboratory. 



^Grice Marine Biological Laboratory, The College of Charleston, 

 Charleston, SC 29412 and Marine Resources Research Institute, 

 P.O. Box 12559, Charleston, SC 29401; present address: Depart- 

 ment of Zoology and Institute of Ecology, University of Georgia, 

 Athens, GA 30602. 



been ascertained from ichthyoplankton surveys in 

 the eastern Gulf of Mexico (Aprieto 1974; Leak 

 1981). In addition. Leak (1981) determined larval 

 mortality and production, and estimated biomass 

 and potential yield of round scad in the eastern Gulf 

 of Mexico. The objectives of this study were to pro- 

 vide information on seasonal distributions, rela- 

 tive abundance, reproduction, feeding habits, age, 

 and growth of round scad in the South Atlantic 

 Bight. 



METHODS 



Seasonal Distribution and 

 Relative Abundance 



A stratified random sampling design (Grosslein 

 1969) was used to assign trawling stations within 

 six depth zones (9-18 m, 19-27 m, 28-55 m, 56-110 

 m, 111-183 m, 184-366 m) on nine seasonal cruises 

 (Table 1). A total of 739 stations were completed on 

 the continental shelf and upper continental slope 

 between Cape Fear, NC and Cape Canaveral, FL. 

 Fishes were captured in a 3/4 scale version of a 

 "Yankee No. 36" otter trawl (Wilk and Silverman 

 1976) with a 11.9 m headrope, a 16.5 m footrope, 

 and a 1.3 cm stretch mesh cod end liner. Although 

 catches of pelagic fishes by bottom trawls seldom 

 provide accurate estimates of absolute abundance 

 of these species, they probably do reflect relative 



Manuscript accepted December 1986. 

 FISHERY BULLETIN: VOL. 85. NO. 2, 1987. 



251 



