Table 5. --Fork length and weight of shad, 



by age, from the St. Johns, York, and 



Connecticut Rivers, 1960 



Juvenile shad grow rapidly in fresh water, 

 although the rate of growth and size at amy 

 given time may vary between areas. Young 

 shad collected in early October in the Con- 

 necticut River below Hadley Falls Dam at 

 Holyoke, Mass., ranged in fork length from 

 3.1 to 4.2 in. (250 specimens) whereas those 

 collected above the dam ranged from 3.7 to 5 

 in. (255 specimens). Young caught in the 

 Hudson River in late September ranged from 

 2.5 to 3.1 in. fork length (400 specimens); in 

 Chesapeake Bay tributaries in mid-September, 

 2.7 to 3,5 in. (550 specimens); in southern 

 streams in mid-August, 2 to 2.5 in. (400 

 specimens). Average lengths of juveniles from 

 the Hudson River at the end of each month 

 were: June, 0.6 in.; July, 1.9 in.; August, 2.4 

 in.; September, 3 in,; and October, 3.5 in. 



MORTALITY 



Mortality of adult shad is caused mainly by 

 (1) fishing, (2) natural causes, or (3) predators 

 and parasites. 



Fishing Mortality 



The annual fishing mortality rate within 

 rivers is known for a number of shad popula- 

 tions. In the South Atlantic streams, the esti- 

 mated rate varied from a low of 15 percent 

 in the St. Johns River in 1957 (Walburg, 1960a) 

 to a high of 57 percent in the Ogeechee River 



in 1954 (Sykes, 1956). In Chesapeake Bay 

 tributaries, it varied from 45 percent in the 

 York River in 1959 (Nichols and Massmann, 

 1963) to 73 percent in the James River in 1952 

 (Walburg and Sykes, 1957). In the Hudson 

 River, the rate varied from 20 percent in 

 1916 to 79 percent in 1947 (Talbot, 1954). 

 In the Connecticut River, the rate varied 

 from 24 percent in 1956 to 85 percent in 

 1946. 



Natural Mortality 



Few studies have been made to determine 

 natural mortality of adult shad. Fredin (1954) 

 compared the abundance of 6- to 7-yr.-old 

 fish taken from the Connecticut River in 1946 

 and 1947 and estimated that the extraneous 

 mortality rate (deaths occurring between fish- 

 ing seasons) was 36 percent. Walburg (1961), 

 who studied age- and spawning-group fre- 

 quencies for fish taken in the Connecticut 

 River from 1956-59, estimated that the total 

 annual mortality was 73 percent. The average 

 annual natural mortality for these years was 

 estimated to be 58 percent. Whitney (1961) 

 estimated that the rate of survival of adult 

 shad after spawning in the Susquehanna River, 

 based on tag returns, was about 12 percent 

 for males and 26 percent for females between 



1958 and 1959, whereas the survival between 



1959 and I960 was estimated as 2 percent for 

 males and 16 percent for females. A high 

 mortality of adult shad in all Atlantic coast 

 populations south of Cape Hatteras, N.C., is 

 verified by the scarcity of older fish in the 

 catch and the fact that all fish examined were 

 spawning for the first time. 



Predators 



Shad are prolific spawners, but many eggs 

 are not fertilized, and others are eaten by 

 fish and other water animals. The Americaui 

 eel, Anguilla rostrata , and catfishes, Ictalurus 

 spp, feed on the eggs. Eels often attack fe- 

 males caught in gill nets amd devour the eggs. 

 The development of fungus is one of the 

 greatest dangers to eggs in the natural 

 state. Mud brought down by heavy rains 

 may bury and suffocate many eggs (Leach, 

 1925). 



Young shad are caught by predators, and 

 many do not survive their few months' stay 

 in the rivers. During rearing at the Linlithgo 

 station on the Hudson River, great care was 

 needed to protect young shad from eels that 

 entered the ponds through water-supply pipes 

 (The New York Conservation Commission of 

 Fisheries, 1911-12). Striped bass, Roccus 

 saxatilis . prey heavily on the young (Shapo- 

 valov, 1936; Hollis, 1952). 



10 



