358 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



The problem is a complex one and difficult of adequate treatment. In the first 

 place, if the truth of the above contention, that the mackerel has probably adjusted 

 itself to the fisheries and that its numbers have in consequence maintained a fairly 

 even balance be admitted, then it follows that each generation must produce a 

 number of eggs sufficient, when all deductions for casualties are made, to give rise to 

 an equal number of mature breeders. That is, the number of breeders must remain 

 practically constant in successive generations. As in the mackerel the two sexes are 

 about equally divided in numbers, it also follows that from all of the eggs annually 

 produced by a female but two on the average grow to be breeding fish. The total 

 number of eggs produced by a mackerel during the spawning season has been 

 variously estimated at from 363,000 to 680,000. Let us fix the average number near 

 the lower limit. There results the conclusion that about 200,000 eggs are required, 

 under natural conditions, to produce one breeding fish. 



The average annual catch of the Massachusetts fleet is about 230,000 barrels, 

 representing roundly, according to a somewhat hasty estimate, about 32,000,000 fish 

 of three years and older, 23,000,000 of two years, and 12,000,000 of one year. The first 

 are all fish of breeding age, and perhaps some of the two-year-olds also are. The 

 poor catch of the year 1877 fell below this average to the extent of about 21,000,000 

 fish of the largest size and 8,000,000 two-year olds, while of younger fish the average 

 was just equaled. Suppose that the problem is to make good this deficit by arti- 

 ficially propagated fish and that for the sake of clearness we leave out of consideration 

 any disturbing factors. In order to produce this result, a sufficient number of eggs 

 must have been handled in 1874 to produce, three years later, 21,000,000 mature fish; 

 and iu 1875 to produce, two years later, 8,000,000 fish of the size usually classed as 

 No. 3's. And this leaves out of consideration the number of fish which would have 

 been destroyed by the fisheries and other causes in the interval between 1874-1877, as 

 well as the obvious fact that of those which survived only a small part would be taken 

 by the fishermen. To make good this shortage for 1877 by the natural processes of 

 spawning, under average conditions would require a number of eggs equal to 21,000,000 

 multiplied by 200,000.' 



The year taken (1877) is, of course, an extreme case, though the present decade has 

 seen much worse; but the goal which should be aimed at in our fishery development 

 is to supply the entire quantity consumed in this country. Besides, the year 1874, 

 when this hypothetical experiment in practical propagation is supposed to have been 

 l>egun, was particularly favorable to its successful issue. The Massachusetts inspec- 

 tion passed 180,000 barrels of Nos. I and 2, or about 50,00o,ooo of fish large enough 

 to be breeding. Now, suppose that one-half of these were males and that one-third of 

 the fish were taken in actual spawning condition. Let us further assume that all 

 of these 8,500,000 spawning females were actually stripped and the entire yield of 

 eggs utilized. It is peculiar of the mackerel and many other active fishes that only ;i 

 portion of the eggs produced in the season mature at one time. The mackerel yields 

 on the average, when stripped, about 40.000 eggs. This would give a total number of 

 eggs secured of 8,500,000 multiplied by 40,000, or 340,000,000,000. 



1 It is, of course, understood that the 21,000,000 includes fish of several ages. In the calculation 

 all are regarded as being 3 years old, owing to the absence of any data upon which to hase a 

 separation among those of 3 years and older. The writer's perM>n:il examinations of mackerel for 

 several years past convince him that the number of mackerel of :* years of age captured is at least 

 equal to all those of greater age combined, making a very liberal allowance in favor of the latter. 

 The result of the calculation would not, therefore, be materially affected. 



