SMITH: DISTRIBUTION OF SUMMER FLOUNDER 



By SO doing, the mass of cold water may play 

 a major role in the success or failure of spawn- 

 ing off the Middle Atlantic States, depending 

 on the time when it becomes mixed with sur- 

 rounding water by late summer and fall storms. 



By November, water was mixed and tem- 

 peratures uniform from surface to bottom, 

 except at those stations on the seaward end 

 of transects. Eggs occurred in greatest numbers 

 off northern Virginia, over 11.7°C bottom 

 water, and off the outer banks of North Carolina, 

 where the bottom temperature was 15.0 °C. 

 The northern limit of the principal area of 

 distribution was along the transect off Great 

 Egg Inlet, N.J., where we started the cruise. 

 At that time, bottom temperatures exceeded 

 12°C (Figure 10). By the time we began 

 sampling the four northernmost transects (see 

 Table 1). bottom temperatures had fallen below 

 12 °C and spawning had practically ended in 

 the northern part of the survey area. It con- 

 tinued in the southern part, where in December 

 (1965) we caught eggs over bottom tempera- 

 tures of 12° to 19°C (Figure 10). By late 

 January, bottom temperatures were less than 

 12 °C at all but five stations, and we caught 

 eggs only at the most southerly one, where 

 the bottom temperature was 17.8°C. 



Presuming that spawing occurs on the 

 bottom, it is limited to a narrow temperature 

 range. The eggs, however, which subsequently 

 rise, are evidently more temperature tolerant 

 than their spawning parents, for we found 

 them at water temperatures as cold as 9.1°C 

 and as warm as 22.9°C, though mostly from 

 13.0° to 17.9°C. Judging from the hatching 

 time for artificially fertilized eggs, reported 

 by Smith and Fahay (1970), those taken off- 

 shore in 9.1°C water required about 142 hr 

 to hatch; those taken at 22.9°C, only 56 hr. 

 Most of the eggs collected during the survey 

 would have hatched 74 to 94 hr after fertiliza- 

 tion. Although larvae occurred over a still 

 wider mean temperature range than eggs (0° 

 to 23.1°C), they were most abundant at mean 

 temperatures of 9.0° to 17.9°C (Appendix Table 

 2). Other workers also have captured young 

 summer flounder over a wide range of both 

 temperature and salinity. Williams and Deubler 

 (1968) caught postlarvae in Pamlico Sound 



water ranging in temperature from 2° to 22°C 

 and in salinity 0.02 to 35.0"7no. Tagatz and 

 Dudley (1961) caught young of 11 to 180 mm 

 in length at temperatures between 9.4° and 

 31.2 °C and salinities between 8.7 and 37.0'7o... 

 and Deubler and White (1962) kept post larvae 

 for 33 days in water with a salinity of 40"/ oo- 



GEOGRAPHICAL SPAWNING AREAS 

 AND SPAWNING POPULATIONS 



Although summer flounder occur occasionally 

 as far north as Maine and as far south as 

 Florida, fishing records indicate that they are 

 most abundant from Cape Cod to Cape Lookout. 

 Thus, it is doubtful that much spawning oc- 

 curred north or east of our northernmost 

 transect. The most important spawning grounds 

 within the survey area were off New York 

 and New Jersey. We caught the greatest 

 numbers of eggs within 46 km of shore. Larvae 

 were most abundant 22 to 83 km offshore. In 

 some instances, we caught the young stages 

 at our most seaward stations, but, considering 

 the known offshore range of adults, it is 

 unlikely that significant numbers of eggs or 

 larvae occurred beyond our outermost stations. 

 The numbers of eggs and larvae were relatively 

 low off Virginia, increased off the outer banks 

 of North Carolina, and declined off Cape 

 Lookout (Appendix Table 3). Cape Lookout, 

 however, should not be considered the southern 

 limit of spawning, for we caught larvae as far 

 south as Daytona Beach, Fla., in January 1968. 

 Plankton collections south of Cape Lookout 

 in 1953, 1954, and 1967^ contained summer 

 flounder larvae (Figure 11). More sampling 

 is needed to assess the importance of spawning 

 grounds south of Cape Lookout. 



Although research on summer flounder has 

 been sporadic and limited in geographic scope, 

 there is mounting evidence that separate 

 spawning populations exist. The occurrence 

 of distinct areas of egg and lan'ae abundance 

 at different times of the spawning season; the 

 tag returns of Poole (1962) and Murawski 

 (1970), indicating a general inshore-offshore 



^Unpublished data on file at Middle Atlantic Coastal 

 Fisheries Center, National Marine Fisheries Service. 

 Highlands, N.J. 07732. 



533 



