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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Figure 7. — Scale from 6-year-old marked shad spawning for the first time. 



agreement with known age established by mark- 

 ing. These findings indicate that the method used 

 to age shad (Gating, 1953) is valid and that annuli 

 and spawning marks are true indicators of age. 



SUMMARY 



One hundred thousand juvenile shad from the 

 Connecticut River were marked by removal of the 

 right pelvic fin, in 1952. Tlie objective of this pi'O- 

 gram was to recover marked fish of known age in 

 future years, to validate the use of annuli and 

 spa^vning marks for determining age of shad. 



Marked fish were first recovered in the Connecti- 

 cut River in 1956 with subsequent recoveries in 

 1957 and 1958. Fish with marked and abnormal 

 fins were collected in each of these years. Twenty- 

 eight were collected in 1956, 132 in 1957, and 57 

 in 1958. 



The pelvic fin section from each fish sampled 

 was X-rayed and classified as follows: (1) 



marked, (2) malformed, and (3) missing. 

 Marked fins were identified by an enlargement at 

 the distal end of the radial bones at the point of 

 separation from the dermal fin rays. Pelvic fin 

 sections were classified as malformed, when there 

 was no enlargement of tlie distal end of the radials. 

 Missing fins were classified as to the fin or fins af- 

 fected. The number of marked fish collected each 

 year was determined from a study of pelvic fin 

 sections and radiographs. 



Scales from sampled shad were read for total 

 age and number of times each fish had previously 

 spawned. The 1956 recoveries of mai'ked shad 

 were 4-year-oId fish spawning for the first time. 

 Those collected in 1957 were 5-year-old fish, with 

 I'ecoveries divided between first and second year 

 spawnei-s. Fish spawning for the second time had 

 first spawned in 1956. Marked fish collected in 

 1958 were 6 years old and consisted of first-, sec- 

 ond-, and third-year spawners. Those spawning 



