REPORT OF THE COMMISSIONER OF FISHERIES XXXV 



000 pounds of fish annually for many years to American ports alone. 

 The total productivity of the area never has been determined, due 

 to the fact that the fishery is exploited by the ships of several 

 nations from whom statistics of the yield are not available. How- 

 ever, with the development of improved methods of preparation 

 and marketing, there is little doubt but that these fisheries are enter- 

 ing upon an era of unprecedented exploitation that will test to the 

 utmost the capacity of the stock to supply the demand. Therefore 

 it behooves American industry to safeguard itself against over- 

 exploitation, ultimate depletion of the fishery, and economic disaster, 

 by careful and continuous observations on the condition of this 

 resource. Accordingly, intensive investigations of the fish stock and 

 of the food supply upon which it depends have been pursued ener- 

 getically by the bureau for several years. 



Investigations of the fisheries for cod, pollock, and haddock, of 

 the spawning habits and early development of the fish, of the plank- 

 ton organisms, and of the physical factors of environment have been 

 conducted during the past year. The study of the stock of adidt 

 cod, of its age and rate of growth, its segregation or migrations 

 from bank to bank, and the various shore areas has received par- 

 ticular attention. During the past three years 36,792 cod, pollock, 

 and haddock were tagged and liberated, and 1,672 of these, or 4^ 

 per cent, have been recaptured. During the past fiscal year 7,943 

 of these fish were tagged and liberated. By careful analysis of the 

 tagging records much has been learned of the migrations and 

 habits of these fish. The outstanding results of these experiments 

 are as follows : Cod tagged on Nantucket Shoals migrate each fall 

 to the shore waters of Rhode Island, Long Island, and New Jersey. 

 The majority are retaken on Nantucket Shoals where they were 

 tagged, only a few being found in South Channel, on Georges 

 Bank, or north of Cape Cod. Cod tagged in Massachusetts Bay 

 or on Stellwagon Bank apparently scatter both north and south, 

 but fish tagged on Platts Bank and the southern coast of Maine are 

 quite localized, showing little migration at all. Farther north, 

 however, cod tagged at Mount Desert frequently were recaptured to 

 the north in the Bay of Fundy, although fishing was so intensive 

 that over 20 per cent of all the tagged fish liberated were recaptured 

 locally and returned. A collection of over 10,000 scales from cod 

 and other fishes made during the tagging experiment of 1924 and 

 1925 is being studied to determine ages and rates of growth in 

 the various areas to supplement the knowledge of the stock of fish. 



In connection with these studies detailed investigations of the 

 occurrence of eggs and larvae are being conducted. These are of 

 importance in an understanding of possible depletion and variation 

 in abundance, for it has been found that the cod found spawning 

 in the western inshore waters of Massachusetts Bay produce eggs 

 that do not remain in that area to renew the population but art' 

 carried out of the bay and develop in other regions. The same is 

 true in Ipswich Bay, although it has not yet been discovered if 

 these eggs are carried into Massachusetts Bay or out to sea, thus 

 stocking offshore banks. 



During the past year a notable contribution to our knowledge of 

 the fisheries has been made in a report on the " Plankton of the 

 offshore waters of the Gulf of Maine." A report on the physical 



