222 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Is it possible to determine the number of survivals in an animal like the lobster .' 

 We can not fix the number positively, but we can fix a maximum limit beyond which 

 we may be sure, reasoning from known facts, the number of survivals can not pass. 

 F.y xurriralti 1 mean the number of eggs which develop and grow up to maturity, for 

 death, at whatever point occurring at this period, means evil to the species in exactly 

 the same degree. In order to maintain the species at an equilibrium it is only neces- 

 sary that each female produce two adults in the course of her life, whether it be long 

 or short. Then there will be neither increase nor diminution, but the species will hold 

 its own. If more than two adults are raised from the eggs of each female in a given 

 period, then the species must increase; if less, it must diminish. Under present con- 

 ditions it is generally agreed that the lobster is declining, which means that each 

 adult female produces less than two sexually mature individuals to take the place of 

 their parents. 



Spawning lobsters may produce as few as 3,000 eggs and as many as 90,000 or 

 100,000, the number of eggs laid increasing very rapidly in proportion to the increase 

 in size, according to the law given above. While a 10-inch lobster produces on the 

 average 10,000 eggs, a 12 inch lobster bears twice as many, and a 14-inch lobster nearly 

 four times as many, or 40,000. Although sexually mature lobsters can produce eggs 

 only once in two years, many live to hatch several broods and give rise to hundreds 

 of thousands of young. Kemembering that females become mature when from 8 to 12 

 inches long, to be on the safe side we may assume that on the average they mature at 

 the length of 10 inches. A 10-inch lobster produces on the average about 10,000 eggs. 

 Considering all the facts, it is erring on the safe side to assume that the average 

 number of eggs produced by all lobsters which have spawned is 10,000. It is probably 

 much greater than this. It can not certainly be less. Since it is necessary that only 

 two of this number should survive to maintain the species at an equilibrium, we can 

 get some idea of the amount of destruction which is wrought under existing circum- 

 stances. A survival of 2 in 10,000 or 1 in 5,000 is probably even greater than actually 

 occurs. The remainder of this large number must be destroyed in one of two ways, 

 by nature and by man, who assists nature in this work after the young are able to be 

 caught in his traps. It can make no difference in the result what the agent of this 

 destruction is, whether it is the ocean current, the storm lashing the rock-bound 

 coast, the codfish, or man, except in so far as the evil wrought by man may be under 

 control. If we award to man one-half of the blame, this would imply that instead of 

 a saving of 2 in 10,000, under nature there might be a survival of 4. But such a 

 survival would lead to a greater increase in the species than could probably ever occur. 



What, then, is the ratio of the number of eggs laid to the number of young 

 reared! Allowing that man does one-half of the work of destruction which he 

 certainly does not and allowing an average total production of 10,000 eggs to each 

 female that has spawned at all undoubtedly too small a number the species would 

 be maintained under nature by a survival of 2 in every 10,000, or 1 in 5,000, if man 

 did not interfere. A survival of 4 in every 10,000, or 2 in 5,000, would keep up the 

 present stock with the added drain which man puts upon it. Considering that the 

 fishery is declining, it can be maintained with a considerable degree of confidence 

 that a survival of 1 in 5,000 is a very liberal allowance. 



These considerations have a direct bearing upon the efficiency of the present 

 methods of artificial propagation, which consist of stripping off the eggs from the 



