In certain instances significant differences were found in meristic counts between young shad from neighboring streams and among streams within large geographical areas. Whether the cause of these differences was primarily genetic or was environmental variation under which the fish developed, or a combination of both, would not affect the findings. Physical and chemical data on the environment at spawning time were not available, so the relation between differences or shifts in meristic counts between two separate rivers and environmental factors was not known. Lindsey (1957), Raney and Woolcott (1955),. and Tåning (1952), and others, although working on species other than shad, listed temperature as the obvious environmental factor that may produce differences at the time these characters are formed in the embryo. Although shad spawn earlier in southern rivers and progressively later in northern rivers, widely separated populations spawn and eggs and larvae develop under about the same water temperature range. Laboratory rearing of the

species under controlled conditions would be needed to demonstrate clearly the relation between meristic counts and temperature.

There was no consistent latitudinal cline in the meristic counts examined over the entire geographic range sampled. Fin raycounts were higher in southern rivers and lower in northern rivers, with intermediate counts in between. Scute counts were higher in northern rivers and lower in southern rivers. The Connecticut River samples had the lowest mean count in pectoral and dorsal fin rays, and the St. Johns River samples had the highest mean counts in dorsal and anal fin rays. However, the scute counts, which showed the greatest difference, reversed this pattern with the high in the Hudson River being more than one unit larger than the low counts in the Neuse River.

mean

There were slight variations in meristic counts on juvenile shad between years and locations within a river, but these were not significant and were small compared to the differences in the counts between rivers. The differences in meristic counts between rivers indicated that discrete juvenile populations exist. For a better understanding of shad populations, future work should include studies of the relation between the meristic counts of juvenile shad and environmental variations under which the fish developed.

SUMMARY

To test if shad populations in various rivers could be separated by differences in meristic count, collections of juvenile shad from 10 rivers along the Atlantic coast were compared by analysis of variance. Counts of pectoral, dorsal, and anal fin rays and scutes were used.

Differences in counts of meristic characteristics within individual rivers and between rivers within geographical areas were as follows:

1. Within individual rivers, no significant differences were found between locations and between years except between locations for pectoral fin rays in the Connecticut River.

2. In the North Atlantic area, significant differences were found between the Hudson and Connecticut Rivers for all counts except anal fin rays.

3. In Chesapeake Bay tributaries, significant differences were found between the York and James Rivers for all counts; between the Rappahannock and James Rivers, the Rappahannock and York Rivers, and the James and Susquehanna Rivers for three of the counts; and between the Rappahannock and Susquehanna, and the York and Susquehanna Rivers for two of the counts.

4. In the South Atlantic area, significant differences were found between the Neuse and Edisto Rivers, and the Neuse and St. Johns

LEACH, GLEN C.

1925. Artificial propagation of shad. [U.S.] Bur. Fish., Rep. U.S. Comm. Fish., 1924, append. 8 (Doc. 981):459-486.

LEHMAN, BURTON A.

1953. Fecundity of Hudson River shad. U.S. Fish Wildl. Serv., Res. Rep. 33, 8 p. LINDSEY, C. c.

1957. The bearing of experimental meristic studies on racial analyses of fish populations. Proc. Ninth Pac. Sci. Congr. 10:54-58.

NICHOLS, PAUL R.

1960. Homing tendency of American shad, Alosa sapidissima, in the York River, Virginia. Chesapeake Sci. 1(3-4):200-201. RANEY, EDWARD C., and WILLIAM S. WOOLCOTT.

1955. Races of the striped bass, Roccus saxatilis (Walbaum), in southeastern United States. J. Wildl. Manage. 19(4): 444-450.

SNEDECOR, GEORGE W. 1956. Statistical methods applied to experiments in agriculture and biology (5th ed.). Iowa State Coll. Press, Ames, Iowa, 534 p.

STEEL, ROBERT G. D., and JAMES H. TORRIE.

1960. Principles and procedures of statistics with special reference to the biological sciences. McGraw-Hill Book Company, Inc., New York, p. 119-123.

TALBOT, GERALD B., and JAMES E. SYKES. 1958. Atlantic coast migration of American shad. U.S. Fish Wildl. Serv., Fish. Bull. 58:473-490.

TÅNING, A. VEDEL.

1952. Experimental study of meristic characters in fishes. Biol. Rev. 27:169-193. VLADY KOV, V. D., and D. H. WALLACE. 1938. Remarks on populations of the shad (Alosa sapidissima) along the Atlantic coast region. Trans. Amer. Fish. Soc. 67:52-66.

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GPO 897-665