332 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



mackerel. 66 When there is an abundant crop of 

 young mackerel, the fishing is good during the 

 next several years, but the catches then fall off, if 

 another good brood does not soon appear upon the 

 scene. The course of events since the low point 

 in 1910 may then be reconstructed about as follows: 



In 1910, when the stock of mackerel was at its 

 lowest, most of the fish caught were large, sug- 

 gesting that few young had survived for several 

 years past. Unfortunately, no information is 

 available as to the composition of the population 

 from the point of view of size for the next three 

 years, when the catch was progressively somewhat 

 larger, but great numbers of small fish, (apparently 

 yearlings), were reported in 1912, pointing to a 

 good breeding season in 1910, in 1911, or in both. 

 In 1914 fish smaller than 1% pounds again formed 

 nearly 60 percent, by weight, of the catch in and 

 off the Gulf of Maine, and approximately 80 per- 

 cent in 1915, with an even greater preponderance 

 in actual numbers between small (young) fish 

 and large (old). These little fish, hatched dur- 

 ing the period 1910 to 1912 or 1913, were respon- 

 sible, as they grew, for the fairly good catches made 

 in the Gulf in 1916 and 1917. 67 But the produc- 

 tion of fry must have been very poor in 1916 and 

 1917, for the Gulf of Maine catch was only about 

 one-seventh as great in 1919 as it had been in 

 1916. And reproduction must have practically 

 failed in 1918 or in 1919, for the mackerel caught 

 in 1920 ran very large, both south of New York 

 that spring, and in our Gulf during that summer 

 and autumn. 



The population was now back again in about the 

 same state as it had been in 1910, the cycle having 

 run through a period of 10 years. The parallel goes 

 further, too, for 1921 must have seen a wave of 

 production to account for the swarms of small 

 fish that appeared along the New England coast 

 from Woods Hole to Mount Desert during the 

 summer of 1922. This again presaged a great in- 

 crease in the catches of mackerel for the next few 

 years to come (more than 11 million pounds were 

 taken in the Gulf of Maine in 1923). And Sette's 

 studies show that 1923 was another productive 

 year, resulting in a catch more than twice as great 

 in 1925 as it had been in 1923, and about 3 times 



as great in 1926. 68 The very large catch of about 

 59 million pounds in the Gulf in 1932 was pre- 

 ceded similarly by the presence of great numbers 

 of yearlings in 1929, evidence of successful repro- 

 duction in 1928. 



Thus, it seems that the proportion of fish of 

 different ages in the catch in any one year may 

 be used as a basis for predicting the success or 

 failure of the run of mackerel for the next year; 

 such predictions have in fact been attempted by 

 Sette 69 with fair success. 



No record has been kept, so far as we know, of 

 the relative numbers of mackerel of different ages, 

 of late years. But a failure of reproduction, fol- 

 lowed by a slump in the catch, may come at any 

 time, for history has a way of repeating itself, 

 especially where fishes are concerned. 



Nothing definite is known as to what determines 

 the success or failure of reproduction of the mack- 

 erel in any given year. Towings by the U. S. 

 Bureau of Fisheries make it likely that the actual 

 production of eggs is usually sufficient. But the 

 vitality of the eggs spawned in any given year 

 goes back to the physiological condition of the 

 parents. And studies of the composition of the 

 stock of fish in periods of high production and of 

 low suggest that there is some correlation between 

 the number of adult mackerel existing in the sea 

 at any time, and the success with which they 

 breed, for it seems that years when great numbers 

 of fry survive always fall when the parent fish 

 are scarce, average large, and also average very 

 fat (by general report). 



One hypothesis is that the mackerel tend to 

 grow fast when there are only a few of them and 

 go into the winter in excellent condition, hence 

 are able to produce eggs of high vitality and in 

 abundance; but they do not fare so well indi- 

 vidually when plentiful, hence, do not emerge 

 from their winter quarters in as good physio- 

 logical condition in spring, so that fertilization 

 and incubation may be less successful, and such 

 larvae as hatch may be less strong. On the other 

 hand, all this may be insignificant as compared 

 with the success or failure of the larvae in sur- 

 viving the dangers and difficulties of subsistence 

 that confront them. Onslaughts by enemies, 



• Sec especially Sette, U. S. Bur. Fish., Fishery Circular No. 4, 1931. 

 « Qulf of Maine catch, 16,391,095 pounds in 1916; 16,021 ,619 pounds In 1917. 



« Oulf of Maine catch, 11,007,676 pounds In 1923; 25,475,876 pounds In 1925; 

 33,152,766 pounds in 1926. 



• U. S. Bur. Fish., Fish. Circ, No. 4, 1931; No. 10, 1932; No. 14, 1933; No. 

 17, 1934; Fishing Oazette, vol. 60, No. 5, 1933, pp. 9 and 21. 



