192 



FISHERY BULLETIN OF THE FISH AND "WILDLIFE SERVICE 



The only regular seasonal migrations that the cod 

 within our Gulf are known to carry out are: (a) 

 their concentrations on their spawning grounds, 

 followed by their dispersal therce after they are 

 spawned out; and (b) a tendency of the fish 

 living closest in shore and shoalest to shift depth 

 with the season, according to the temperature of 

 the water. Thus the cod tend to work in shore, 

 and shoaler, around Massachusetts Bay in autumn, 

 to work out into deeper (herce cooler) water 

 again for the summer. On the other hand, local 

 fishermen report that the cod abandon the 

 shoalest (7-10-fathom) parts of Nantucket Shoals, 

 after the water there has been chilled by the first 

 heavy snows, to congregate from January until 

 April in the deeper (12-20-fathom) channels 

 (warmer in this case.). 



Spawning grounds and season. — Thanks to 

 Earll's painstaking studies, and to the large scale 

 on which the Bureau of Fisheries subsequently 

 collected and hatched cod eggs at the Gloucester 

 and Woods Hole hatcheries, the spawning season 

 and the major spawning grounds of the cod are 

 fairly well known for the coastal waters between 

 Nantucket Shoals and the Bay of Fundy. 



According to the reports of fishermen and to 

 W. F. Clapp's first-hand experience, large bodies 

 of cod spawn on the eastern part of Georges Bank 

 east of Georges shoal, centering at about latitude 

 41°21' to 41°31', longitude 66°50', to 67° F. in 

 about 35 fathoms of water. Vague rumors are 

 our only indication as to where and when cod 

 spawn on other parts of Georges; they may do so 

 there, wherever the water is shoaler than 35 to 40 

 fathoms. And there is every reason to suppose 

 that they spawn regularly on Brown's Bank, 

 though we have no definite record of it. 



The broken bottom of Nantucket Shoals, east 

 and south of Nantucket Island (fig. 94), has long 

 been known as a center of abundance for ripe cod 

 fish in late autumn and early winter. 



So far as we can learn few cod, if any, spawn on 

 the sandy bottom along the outer shores of Cape 

 Cod. But great numbers of ripe fish congregate 

 in Massachusetts Bay on well-defined grounds 3 

 to 10 miles offshore, extending from abreast of 

 Sandwich (some 12 miles south of Plymouth) to 

 Minots Light off Cohasset. Years ago many 

 cod also spawned over a small area off Boston 

 Lighthouse and thence northward toward Bakers 

 Island. Few breeding fish have been reported 



there of late, however, probably because this 

 general locality has been used as the dumping 

 ground for the refuse from Boston, but a few 

 still spawn on various small rocky patches off 

 Gloucester. 



Figure 94.- — Chief spawning grounds of cod in the western 

 side of the Gulf of Maine. 



The Ipswich Bay region, where large schools of 

 ripe cod gather in winter and spring, is probably 

 the most important center of production for the 

 inner part of the Gulf of Maine north of Cape Ann, 

 but this ground, like the Massachusetts Bay 

 spawning ground, is limited to a rather small and 

 well defined area extending only from a few miles 

 south of the Isles of Shoals to abreast of the 

 mouth of the Merrimac River and (less produc- 

 tively) to Cape Ann, chiefly within 4 to 6 miles of 

 land. A glance at the chart (fig. 94) will show how 

 limited the more important breeding grounds of 

 the southwestern part of the Gulf of Maine are in 

 extent (not more than 300 square miles in all) 



