Southern flounder, continued 



range from 595 to 910 mm TL(Ginsburg 1952, Hoese 

 and Moore 1977, Stokes 1977). 



Food and Feeding 



Trophic Mode : The southern flounder is carnivorous 

 during all life stages. Larvae feed on pelagic zooplank- 

 ton, while juveniles and adults feed on crustaceans, 

 and benthic and pelagic fishes (Gilbert 1986). Young 

 southern flounder are dominant predators in Texas 

 estuaries on small brown shrimp during the spring 

 (Minelloetal. 1989). 



Food Items : Larvae feed on zooplankton (Peters 1 971 ). 

 Small crustaceans, particularly mysids, but also grass 

 shrimp, penaeid shrimp, amphipods, and crabs make 

 up the diet of small juveniles (10-160 mm TL) (Diener 

 et al. 1974, Stokes 1977, Minello et al. 1989). Larger 

 juveniles and adults are basically piscivorous, feeding 

 on small benthic and pelagic fishes; but, shrimp, crabs 

 and polychaetes are also utilized to a lesser extent 

 (Darnell 1958, Fox and White 1969, Powell 1974, 

 Stokes 1977, Powell and Schwartz 1979, Overstreet 

 and Heard 1982). In a North Carolina study, inverte- 

 brate prey included the mysids Mysidopsis bigelowi 

 and Neomysis americana, and fish prey included bay 

 anchovy, spot, and croaker (Fitzhughetal. 1996). The 

 ontogenetic shift to piscivory occurred as fish grew 

 from 70 to 180mmTL. 



Biological Interactions 



Predation : Information on predation of flounder is scarce. 

 Larvae and juveniles are probably the most suscep- 

 tible to predation due to their smaller size. Known and 

 suspected species that prey on flounder species in the 

 Gulf of Mexico are: tiger shark (Galeocerdo cuvier), 

 gafttopsail catfish (Bagre marinus), inshore lizard fish 

 (Synodus foetens), various searobins (family Triglidae), 

 various sculpins (family Cottidae), jewf ish (Epinephelus 

 itaiara), and larger-sized southern flounder (Kemp 

 1949, Miles 1949, Diener et al. 1974, Tanaka et al. 

 1989). 



Factors Influencing Populations : Southern flounder 

 and gulf flounder are very difficult to distinguish from 

 each other during early life stages (Woolcott et al. 

 1968). Early stages are often summarized as 

 "Paralichthys species" (King 1971) or just "southern 

 flounder" (Stokes 1 977). Adult southern flounder gen- 

 erally outnumber gulf flounder in the northern Gulf of 

 Mexico, and catches containing the two species are 

 not usually separated. This makes catch data for the 

 two species very hard to analyze. The shrimp fishery 

 unintentionally catches large numbers of juvenile floun- 

 der, almost all of which are discarded (Gunter 1945, 

 Matlock 1991). This reduces the number of sexually 

 immature fish available for recruitment into the fishery. 



Personal Communications 



Fitzhugh, Gary R. NOAA National Marine Fisheries 

 Service, Panama City, FL. 



Hightower, Margot. NOAA National Marine Fisheries 

 Service, Galveston, TX. 



Powell, Allyn B. NOAA National Marine Fisheries 

 Service, Beaufort, NC. 



References 



Arnold, C.R., W.H. Bailey, T.D. Williams, A. Johnson, 

 and J.L. Lasswell. 1977. Laboratory spawning and 

 larval rearing of red drum and southern flounder. Proc. 

 Southeast. Assoc. Fish Wildl. Agen. 31:437-440. 



Darnell, R.M. 1958. Food habits of fishes and larger 

 invertebrates of Lake Pontchartrain, Louisiana, an 

 estuarine community. Publ. Inst. Mar. Sci., Univ. Tex. 

 5:353-416. 



Deubler, E.E., Jr. 1960. Salinity as a factor in the 

 control of growth and survival of postlarvae of the 

 southern flounder, Paralichthys lethostigma. Bull. Mar. 

 Sci. Gulf Caribb. 10:338-345. 



Deubler, E.E., Jr., and G.S. Posner. 1963. Response 

 of postlarval flounders, Paralichthys lethostigma, to 

 water of low oxygen concentrations. Copeia 1 963:31 2- 

 317. 



Diener, R. A., A. Inglis, and G.B.Adams. 1974. Stom- 

 ach contents of fishes from Clear Lake and tributary 

 waters, a Texas estuarine area. Contrib. Mar. Sci. 

 18:7-17. 



Ditty, J.G., G.G. Zieske, and R.F. Shaw. 1988. Sea- 

 sonality and depth distribution of larval fishes in the 

 northern Gulf of Mexico above latitude 26°00'N. Fish. 

 Bull., U.S. 86(4):81 1-823. 



Fischer, W. (ed.). 1978. FAO Species Identification 

 Sheets for Fishery Purposes, Western Central Atlantic 

 (Fishing Area 31), Vol. I. Food and Agriculture Orga- 

 nization of the United Nations, Rome. 



Fitzhugh, G.R., L.B. Crowder, and J. P. Monaghan, Jr. 

 1996. Mechanisms contributing to variable growth in 

 juvenile southern flounder (Paralichthys lethostigma). 

 Can. J. Fish. Aquat. Sci. 53:1964-1973. 



Fox, L.S., and C.J. White. 1969. Feeding habits of the 

 southern flounder, Paralichthys lethostigma, in Barataria 

 Bay, Louisiana. Proc. Louis. Acad. Sci. 32:31-38. 



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