FISHERY BULLETIN: VOL. 71, NO. 2 



movement and a strong tendency of fish to 

 return in subsequent summers to the same 

 area; the short time between departure from 

 the inshore summering grounds and the onset 

 of spawning, which would limit prespawning 

 movement; and, finally, the differences in gill 

 raker and anal ray counts between summer 

 flounder collected at Chesapeake Bay and at 

 Beaufort, N.C. (Ginsburg, 1952) strongly sug- 

 gest the likelihood of different populations. 

 Judging from our survey in 1965-66, one 

 segment of the species appeared to spawn 

 principally north of Delaware Bay, a second 

 from Virginia to Cape Hatteras, and a third 

 south of Cape Hatteras. The biological evidence 

 is supported by commercial landings. The 

 catch from ports between Maryland and Massa- 

 chusetts declined by 66% from 1960 through 

 1967. During the same period, Virginia land- 

 ings fluctuated but a decline was not evident. 

 In North Carolina, landings increased. If effort 

 remained relatively constant along the coast, 

 it is unlikely that such trends would have 

 occurred if the various coastal fisheries de- 

 pended on one population. 



LARVAL MOVEMENTS 



The net transport of water along the Middle 

 Atlantic Bight is generally southerly to south- 

 westerly in the fall (Bumpus and Lauzier, 1965; 

 Norcross and Stanley, 1967). Although pelagic 

 eggs and early larval stages drift in sea cur- 

 rents, it appears that the summer flounder 

 larvae we collected had not drifted far from 

 the spawning areas. Larvae of all stages of 

 development caught off New York and New 

 Jersey, and off North Carolina, were taken 

 in the general vicinity of the eggs (Figures 12 

 to 16). Although there is no evidence to relate 

 the movement of young summer flounder to 

 known current patterns, early juvenile stages 

 have been captured only in estuaries, suggesting 

 that the young fish are estuarine dependent. 

 Their tolerance to wide ranging temperatures 

 and salinities further suggests that they are 

 physiologically adapted to utilize the estuarine 

 zone for nursery grounds. Judging from our 

 collections and the size of specimens collected 

 at inlets along the coast, the shoreward migra- 



tion begins after the young fish metamorphose 

 and become capable swimmers. 



Most of the postlarvae in our collections 

 were caught at night. Of the 114 specimens 

 larger than 9 mm, 91 (80%) were taken after 

 dark. Additional sampling with modified col- 

 lecting gear should confirm whether the sig- 

 nificantly greater nighttime catch resulted from 

 net avoidance during the day or from diel 

 movements of the metamorphosing young fish. 

 Arnold (1969) noted that metamorphosing post- 

 larvae of the European plaice, Pleuronectes 

 platessa, may go quickly to the bottom when 

 not actively swimming. Pearcy (1962) made a 

 similar observation on winter flounder, Pseudo- 

 pleuronectes americanus, considering both the 

 small and large larvae to be partially benthic 

 animals. If postlarval summer flounder behave 

 similarly to the above postlarval flatfishes, then 

 perhaps day-night differences in the catch may 

 reflect periods of low and high activity rather 

 than net avoidance. In this case, the post- 

 larvae would be largely unavailable to our nets 

 when not swimming, which they might do 

 mostly at night. If, on the other hand, the 

 difference between day and night catches re- 

 flects net avoidance, towing speeds in excess 

 of 9.3 km/hr are required to adequately sample 

 postlarval summer flounder when using nets 

 with a mouth opening comparable to a Gulf V. 



ACKNOWLEDGMENTS 



I thank L. A. Walford for his many helpful 

 suggestions during the course of the survey, 

 and for critically reviewing the manuscript; 

 and Elmer J. Gutherz, National Marine Fish- 

 eries Service, Pascagoula, Miss., for providing 

 the additional data on larval summer flounder 

 catches south of Cape Lookout. 



LITERATURE CITED 



Arnold, E. L., Jr. 



1959. The Gulf V plankton sampler. In Galveston 

 Biological Laboratory fishery research for the 

 year ending June 30, 1959, p. 111-113. U.S. Fish 

 Wildl. Serv., Circ. 62. 

 Arnold, G. P. 



1969. The orientation of plaice larvae (Pleuronectes 

 platessa L.) in water currents. J. Exp. Biol. 

 50:785-801. 



534 



