AGE DETERMnSTATION OF AMERICAN SHAD 



165 



FiGUBE 4. — Scale from 4-year-olci marked shad spawning for the first time. 



Tliese included 21 males and 41 females of which 

 40 had either the left, right, or both pelvic fins 

 malformed, and 22 had either the left, right, or 

 both pelvic fins missing. These fish ranged in age 

 from 4 to 7 years. 



Of tlie 57 shad collected in 1958, 18 were classi- 

 fipd as abnoranal. These included 9 males and 9 

 females of which fi had either the left, right, or 

 both pelvic fins malformed and 12 had either the 

 left, right, or both fins missing. These fish ranged 

 in age from 4 to 8 years. 



MARKED FISH RECOVERED 1956 



P'rom a study of pelvic fin sections and radio- 

 graphs it was determined that 17 marked slmd 

 were recovered in 1956. These included 8 males 

 and 9 females of which 3 had no regeneration of 

 the right fin, 5 had one-thiixl regeneration, 4 had 

 two-thirds regeneration, and 5 had complete re- 

 geneiation. Age readings indicated that all 

 marked fish recovered were 4 years old, and spawn- 



ing for the first time ( fig. 4) . Marked males aA'er- 

 aged 1C.4 inches, fork length, and 2.4 pounds in 

 weight. Marked females averaged 17.9 inches, 

 fork length, and 3.2 pounds in weight. 



MARKED FISH RECOVERED 1957 



From a study of pelvic fin sections and radio- 

 graphs it was determined that 72 marked shad 

 were recovered in 1957. Age determined from 

 scale readings indicated that all but two of these 

 fish were 5 years old. The ages of these two fish 

 were 4 and 6 years. The radiographs and scale 

 samples were re-examined and the above results 

 confirmed. Therefore, on the basis of these find- 

 ings, an error of approximately 3 percent exists 

 either in interpretation of radiographs or in age 

 determination. 



The sevent}' 5-year-old fish that were marked 

 included 14 males and 56 females of which 11 had 

 no regeneration of the right jielvic fin, 18 had 

 one-third regeneration, 2G had two-thirds re- 



