COD EGGS IN MASSACHUSETTS BAY, 1924-1925 



259 



eggs obtained by the same hatchery. In addition to this, 430,648,000 pollock eggs 

 also were obtained, 90 per cent of which were derived from gill nets operating around 

 Plymouth and Duxbury. Therefore there was every reason to believe that we would 

 find Massachusetts Bay a haven for an immense number of eggs and fry and a nursery 

 containing young cod in all stages of development. It was expected, too, that this 

 locality would prove favorable for a study of the early life history of this species, its 

 rate of larval development, vertical movements, food during this period, enemies, 

 and the gradual changes in the feeding habits and migrations during the first year of 

 its existence. This investigation was also to form the first of a series of investigations 

 to determine the relative importance of the various fishing banks as production centers. 



PROGRAM AND METHODS 



SPAWNING AREAS EXAMINED 



The area selected for study (fig. 3) comprises the two most important inshore 

 spawning grounds on the New England Coast — Massachusetts Bay and the adjacent 

 grounds to the north (Ipswich Bay). In many respects the conditions are very 

 much alike in the two localities, both being in very shoal water and limited to small 

 and very well defined areas. Off Plymouth the grounds run parallel with the coast, 

 3 to 10 miles from shore, and reach from abreast of Sandwich to Minot's Light. 

 Roughly, the Ipswich grounds extend from the Isle of Shoals to Cape Ann, chiefly 

 within 4 to 6 miles of land. (Bigelow and Welsh, 1925.) The Massachusetts Bay 

 grounds range from 22 to 46 meters in depth and the Ipswich grounds 9 to 46 meters. 

 Although ripe cod may be found in either of these localities from September to May, 

 the height of the spawning season is reached at different times. 



SPAWNING SEASON 



The local fishermen say that the cod strike in the shallow water off Plymouth 

 about November 1 and, according to Bigelow and Welsh (1925), reach the height of 

 their spawning season from December through January, when the water ranges from 

 2.2 to 5.5° C. Hatching records and the abundance of eggs in collections from these 

 grounds in 1925 indicate that spawning fish were plentiful throughout the winter 

 and spring. Until March 20, the Gloucester station received 25,000,000 to 30,000,000 

 cod eggs daily from the Plymouth grounds. 



In Ipswich Bay the height of the cod-spawning season is reached in March, 

 much later than south of Cape Ann, although a few small breeding areas of lesser 

 importance along the north side of Massachusetts Bay, particularly in the vicinity 

 of Pig Rock, off Gloucester, form a haven for spring breeders. Here the season is 

 said to coincide with that at Ipswich, spawning taking place throughout the coldest 

 part of the year, when the temperature ranges from 0.56 to 3.05° C. 



COD AND HADDOCK EGGS 



As haddock eggs in their early stages are indistinguishable from cod eggs, dis- 

 tribution charts must be interpreted in the light of our knowledge of the probable 

 points of origin and the direction of the drift. Were there no drift, it would be pos- 

 sible to determine the relative percentage of cod and haddock eggs containing late 

 embryos and then assume that the earlier stages were present in the same propor- 

 73363—28 2 



