PKOGRESS IN BIOLOGICAL INQUIRIES / 



have been added as far offshore as possible and a line extended from 

 Cape Ann to Boston to determine, if possible, the quantity of eggs 

 that enter the bay from the north. 



An important point in the present investigation is to determine 

 whether the past year was a normal one or whether unusual phy- 

 sical conditions were responsible for the total absence of young 

 cod throughout the breeding season. It was interesting, therefore, 

 to find that the water temperatures during the first cruise (Decem- 

 ber 15 to 19, 1925) were almost identical with those taken over 

 the same period last year. The cooling apparently took place at 

 the same rate in each year. 



Table 4 



Dec. 15 



Massachusetts Bav and 17, to 19 



1925 



Average surface temperature 



Average bottom temperature 



Warmest station (surface) 



Warmest station (bottom) 



Coldest station (surface) 



Coldest station (bottom) 



Due to the absence of young cod in the collections, no information 

 was obtained as to their food and enemies. The physical conditions 

 necessary for the successful hatching of cod are fairly well understood, 

 but almost nothing is known about the biological environment of 

 the cod and its relative importance in determining success or failure 

 in any particular season or locality. Experiments along these lines 

 are being conducted with larval fish obtained from the hatchery at 

 Gloucester. 



In addition to data concerning the cod, pollock, and haddock, the 

 present investigation has increased our knowledge of the distribution, 

 life histories, and occurrence, in the area covered, of 23 other species 

 of young fish that have been identified from the collections. 



MACKEREL INVESTIGATIONS 



During the 1925 mackerel fishing season, investigations on this 

 important fishery were begun. These consisted principally of tagging 

 experiments and the collection of biological data and material such 

 as scales and records of size and maturity for future analyses. Much 

 of this work was carried on in cooperation with the division of fishery 

 industries, which has begun a program intended to accumulate spec- 

 ial statistics on fluctuations of the mackerel fishery. 



The tagging experiments were carried on at Provincetown, Woods 

 Hole, and Casco Bay, approximately 5,600 mackerel being tagged 

 during the season. Of these, 2S6 have been reported as recaptured, 

 some of them having been taken as far east as Fire Island, N. Y., 

 and as far north as Casco Bay. Any general conclusions as to the 

 migrations of mackerel, however, must await the extension of these 

 operations in future years. 



96725—26 2 



