80 THE SCALLOP FISHERY 



The age limit of the scallop ranges from twenty to thirty months. 

 We find that the variation is due to several causes: (1) the spawning 

 season, which makes possible a difference of two months in the age; 

 (2) the environment, favorable or unfavorable, which lengthens or 

 shortens the period of life; (3) seasonal differences, as during a mild 

 winter the old scallops are under less strain than during a severe 

 season; (4) the rate of growth and consequently the size of the scallop, 

 as the small, slow-growing scallops apparently live longer than the 

 large. This was noticeable with the set of 1907 at Monomoy Point, 

 which grew very slowly, as compared with the sets of previous years, 

 owing to the partial closure of the opening to the ocean and the con- 

 sequent lessening of circulation in the Powder Hole during 1908. 

 These scallops in the summer of 1909, when two years old, were scarcely 

 larger than yearlings, and lived until the following September before 

 they began to die, at least six months longer than the normal. In pre- 

 vious years in the Powder Hole a small per cent, of the scallops had 

 lived until May and a still smaller number until August (twenty-five 

 months), but this was the only set, as a whole, to pass to the twenty- 

 sixth month, a fact probably explained by their small size and freedom 

 from foreign growth. 



The above statements are based on the following facts : 



(1) The writer has been able to find very few old scallops (twenty- 

 seven months) during the fall dredging in waters of the Commonwealth. 

 The scallop fishermen report in each locality the same result, with the 

 exceptions above mentioned. This narrows the limit from general prac- 

 tical observation to twenty-seven months. 



(2) The reports of fishermen upon the death of scallops in the 

 last of the winter and in the spring, as well as the great destruction of 

 beds at Dennis, Chatham, etc., prove that the scallop begins to die 

 about the twentieth month of its life. This brings the period of death 

 and decline between the twentieth and twenty-seventh month, or from 

 March until October. 



(3) The sets of 1905, 1906 and 1907 were followed from birth to 

 death at the different scalloping sections by observations at stated in- 

 tervals, and the results, except for the inroads of the scallopers, were 

 conclusively proved by dredging on the scallop grounds. 



(4) Detailed study of the sets of 1905, 1906 and 1907 in the Powder 

 Hole, where the scallops were confined for life, shows conclusively that 

 the average length of life is two years, even when undisturbed by 

 dredging. 



(5) Records from 500 scallops in pens at Mouomoy for growth gave 

 actual figures for death from old age. 



The connection between the limited life of the scallop and the spawn- 

 ing season has been considered under the subject of " Spawning," in 

 chapter III., and it is only necessary to again call the reader's attention 



