FISHES OP THE GULF OF MAINE 205 



In the GuU of Maine June-hatched larvae probably grow to about 3}<2 to 4J^ 

 inches by the end of the summer, fry of that size (obviously of the same season's 

 crop because too small for yearlings) having been taken at Gloucester in August. 

 It is thought they will average about 4 to 6 inches in autumn. This is a smaller 

 size than they are usually credited with. Captain Atwood, for instance, describes 

 them as 63^ to 7 inches long in October, and there may be considerable variation 

 in the length attained by the first winter according as particular lots of eggs are 

 spawned early or late, and to the supply of food. But however this may be, fish 

 of 4}/^ to 7 inches, which can only be yearlings (too small to be older and too large 

 to be yoimger), and known locally as "tacks," are plentiful along the coasts of 

 Massachusetts and Maine in May and June in the occasional years when there is 

 any abundance of small mackerel. 



The subsequent rate of growth has not been traced in as satisfactory a way for 

 the mackerel as for some other fish, neither its scales nor its otohths being as easy 

 to read as those of salmon, herring, cod, etc. It is generally believed, however, 

 that the yearlings grow to a length of 83^ to 11 inches during their second summer, 

 which is corroborated by the fact that the small ones brought in to the Gloucester 

 freezer during the season of 1922 averaged only about 6 inches long when they first 

 appeared on the coast in May or June, but grew to from 7 to 9 inches by the end of 

 August ^° and were said to average about one-third of a pound to half a pound in weight 

 when they left the coast in autumn. Nilsson's scale studies point to 8^ to 12 inches as 

 an average for Swedish mackerel in their second year," suggesting a somewhat more 

 rapid growth for the European fish, but the data are not sufHciently extensive nor 

 precise for the American stock to show whether such a difference is really characteris- 

 tic of the two sides of the Atlantic. It is probable that all American mackerel of 

 13 inches or longer are in their third summer or older. Their later growth has not 

 been traced. Presumably they parallel their European relatives, which, according 

 to measurements of large samples combined with examination of scales and otoliths, ^' 

 average about 12)^ inches in the third summer, 13 inches the fourth, 13J^ inches 

 the fifth, and anywhere from 133-^ to 15 inches in their sixth smnmer, slight 

 departures from which schedule are to be expected on the part of the American fish 

 due to differences in food supply, length of growing season, etc. These Em'opean 

 data suggest that our largest mackerel (16 to 18 inches long) have lived through at 

 least five full years, probably six, and possibly seven or eight. Thus the growth of 

 mackerel is very rapid for the first two or three years and very slow thereafter. 

 This slowing down is probably a corollary of the ripening of the sexual products, 

 breeding being so great a physiological strain that the fish do little more than 

 recover before their winter stagnation sets in. 



Age at maturity. — Some few females ripen when still not more than 11 inches 

 long; most of them, and all males, at 12 to 13 inches. From this it seems that both 

 American and European mackerel usually breed for the first time when 2 full years 



" We owe this information to Captain Thomas, in charge of the freezer. 



" He does not mention the exact seasons at which the fish were tafeen. 



" Nilsson (Publications de Cireonstance No. 69, Consfiil Permanent International pour I'Exploration de la Mer, Vol. XVI, 

 1914, p. 26) and Ehrenbaum (Rapports et Proces-Verbaui, ConsSil Permanent International pour I'Exploration de la Mer, Vol. 

 XIV, 1912). 



