300 Memoir Sears Foundation for Marine Research 



to 1 13 mm long, 26 specimens from the river, all less than a year old; Group 2 — 145 

 to 180 mm long, 4 from salt water, in their second year; Group 3 — 2 10 to 290 mm, 

 7 from salt water, in their third year; Group 4 — 300 to 350 mm, 10 young males 

 entering the river, in their fourth year; Group 5 — 360 to 390 mm, 22 young males 

 entering the river, in their fifth year; Group 6 — 400 to 430 mm, 13 males and 9 

 females, in their fifth, sixth, and seventh years; Group 7 — 440 to 480 mm, 34 males 

 and 9 females, in their sixth, seventh, and eighth years; Group 8 — 490 to 520 mm, 

 28 males and 13 females, in their seventh, eighth, and ninth years; Group 9 — 530 to 

 570 mm, 6 males and 43 females, in their seventh, eighth, ninth, and tenth years; and 

 Group 10 — 580 to 660 mm long, i male and 23 females, in their eighth, ninth, tenth, 

 and eleventh years. 



Young fish from the Bay of Fundy reach a length of 41-45 mm in nine to ten 

 weeks (^J: 74—84). Leim's calculations, based on scale readings of adult fish, in general 

 indicate a rather faster rate of growth for his fish than for those of Borodin. 



Some of the males, according to Borodin, enter the Connecticut River from the 

 sea when they are 300-350 mm long and in their fourth year, as shown in the preceding 

 data. Although the author did not say so, these males undoubtedly were sexually 

 mature, as migration to the rivers seems to be carried out solely for the purpose of spawn- 

 ing. The smallest females that returned to the Connecticut to spawn, according to the 

 same author, were between 400 and 430 mm long and in their fifth, sixth, and seventh 

 years. Therefore, the males seem to become sexually mature at an earlier age than the 

 females. On the other hand, females may reach a greater age; among the older fish ex- 

 amined by Borodin, determined by him to be in their seventh, eighth, ninth, tenth, and 

 eleventh years, there were only 7 males compared to 86 females. Concerning the Bay 

 of Fundy fish, Leim said: "Most of the shad present on the spawning grounds were 

 five years old or over and eight or nine years seems to have been the maximum age 

 represented. Fish under four years of age apparently do not spawn at all" (^J). The 

 discrepancy in the rate of growth and the age of spawning fish, as determined by 

 Borodin and by Leim, may have resulted from a difference in the interpretation of the 

 scale markin_gs, or from a difference in the behavior of two rather widely separated 

 races that may respond differently to the climatic or general environmental condi- 

 tions in which they live. 



Re-production. The average number of eggs produced by a single fish varies between 

 25,000-30,000 {lig: 127). In \}cit Manual of Fish Culture (2: 125) it is stated that the 

 average number is not more than 30,000 but that a single fish has been known to yield 

 between 60,000 and 115,000 eggs. In 1885, one from the Delaware River yielded 

 156,000. In this species, as among others, large fish as a rule produce many more 

 eggs than small ones. 



If all of the large number of eggs produced by a female hatched and reached ma- 

 turity, the progeny would be exceedingly great. However, it is quite certain that nor- 

 mally only a small proportion of the eggs produces fish that live to maturity. The most 

 critical time in the life cycle apparently comes when the larvae have absorbed the yolk 



