128 BULLETIN OF THE BUREAU OF FISHERIES 



The experiment has gone far enough to prove that the humpback can live and 

 grow in the Gulf of Maine during its normal period of marine existence and find 

 its way back to the home streams as the time of sexual maturity draws near. 

 Whether it can multiply to any considerable stock, or even maintain itself by na- 

 tural reproduction without the aid of artificial propagation in the few Maine rivers 

 open to it, remains to be seen. Brief experience with it in the Gulf of Maine sug- 

 gests that the local run will take place in late summer and early autumn as is the 

 case in Alaska. 



Habits. — The humpback runs up small streams indifferently, whether or not 

 lakes occur in their courses. After it enters fresh water it feeds no more, and its 

 digestive organs, like those of all Pacific salmons, shrivel up and atrophy while 

 the changes in form of body and jaws, so characteristic of the breeding male (p. 126), 

 take place. The skin, too, thickens and becomes so spongy that the scales are 

 entirely concealed. The humpback spawns very soon after it enters the rivers, and 

 though it reaches the spawning grounds in fairly good condition (except for a loss 

 of fat), the fins of both sexes soon become frayed, the skin rubs off the jaws, bases 

 of fins, and other prominent places, the tails of the females are worn down to the 

 quick, fungus attacks these open wounds as well as the gills and eyes, and when the 

 last eggs and milt are deposited the spent and exhausted fish finally die. No hump- 

 back ever survives the operation of spawning. 



Spawning takes place in the fall at temperatures of 54° to 60° F. As soon as 

 the yolk sac of the young humpback is absorbed and it is able to swim (which is 

 about the time the ice breaks up in spring) it runs down to the sea. During their 

 first months in salt water the fry linger near the mouths of the home streams, 36 

 where they feed chiefly on copepods and other small crustaceans, on pteropods, 

 and on insects that drift downstream with the current, and occasionally on fish fry. 

 After they are 5 or 6 inches long they move out into deep water, and very little is 

 known of their habits and wanderings thereafter until they reappear on the coast 

 as adults to breed. Large humpbacks have been found full of pelagic Crustacea 

 and launce, evidence that they subsist on a mixed plankton and fish diet, the former 

 probably predominating. No humpback has ever been known to take a trolled 

 spoon or baited hook. 



McMurrich 37 (in 1912) and Gilbert 38 (in 1913) have proved by their studies 

 of its scales that the humpback invariably lives in the sea through one summer, a 

 winter, and well into the second summer, and then comes in to spawn. 



Commercial importance. — The humpback is an excellent food fish when taken 

 in salt water and would be a valuable addition to the Gulf of Maine, but it becomes 

 worthless soon after entering fresh water. 39 



» We owe to Chamberlain (Bureau of Fisheries Document No. 627, Report, U. S. Commissioner of Fisheries, 1906, 112 pp., 

 Pis. I-V) the little we know of the habits of the young humpback. 



>' Proceedings and Transactions, Royal Society of Canada, Third Scries, Vol. VI, May, 1912 (1913), Section IV, pp. 9-28. 



>« Bulletin, U. S. Bureau of Fisheries, Vol. XXXII, 1912 (1914), pp. 3-22, Pis. I-XVII. Washington. 



39 The Pacific "Chinook" salmon (Oncorkynchus tschaicytscha) was introduced in the Merrimac River system by the Com- 

 missioners of Fisheries and Game of the State of Massachusetts in 1916, but the plant seems to have been a failure, for no adults 

 were reported in 1920, the year they would have been expected to return from the sea as mature fish. 



