[33] HISTORY OF THE MACKEREL FISHERY. 123 



" The effect of temperature on the local movements of the mackerel 

 may be recognized in the process employed by fishermen to ' raise' mack- 

 erel by toll-bait, and luring them seawards. The mackerel follow the 

 bait for some distance from shore, where suddenly they cease to bite and 

 disappear. They probably find long exposure to the warm temperature 

 of the surface waters unsuited to their habits, and sink to a cooler zone. 



" Hence the reason why a ' mackerel breeze,' mixing the heated surface 

 water with the cooler understratum, is favorable to prolonged mackerel 

 fishing with bait. The mixing i)roduced by agitation cools the surface 

 and permits the fish to feed for a lengthened period."* 



" The mackerel, like the herring and the cod, seeks cold water for its 

 spawning grounds wherever the Labrador current exercises its influence. 

 Between Block Island and Roman's Land, where the spawning grounds 

 on the United States coast south of Cape Cod are alleged to exist, a 

 thin wedge of the Labrador current stretches far into Long Island 

 Sound ."'t 



"In Massachusetts Bay, where a mackerel spawning ground also 

 exists, as also in the vicinity of Stellwagen Banks, the temperature when 

 observed by Dr. Packard in September ranged from 41^ to 45 degrees, 

 and the fauna resembled the cold-water species on each side of Jeffrey's 

 Ledge. On George's Shoals the marine life is said by Verrill to be the 

 same as that found in the deefjer muddy parts of the Gulf of Saint Law- 

 rence, and indicates a temperature not above 40 degrees, and probably 

 considerably lower. Bradelle Bank, according to Mr. Whiteaves, pre- 

 sents the phenomenon of a small stony patch, tenanted by an assemblage 

 of marine animals which usually inhabit very cold water, and are almost 

 entirely surrounded by another series, which are for the most part prev- 

 alent where the bottom is warmer and more affected by surface condi- 

 tions of temperature.| 



" Wherever the areas are situated where young mackerel are found 

 in the summer, we find near at hand a cold-water zone, either existing 

 as a part of the Labrador current at the surface, or brought up from 

 greater depths by banks and shoals. On the coast of Prince Edward 

 Island, and in the gulf generally, the cold water lies frequently near the 

 shore, because the diurnal tides mix the strata warmed during the day- 

 time with the cold underlying strata. In the estuary of the Saint Law- 

 rence Dr. Kelly found the surface temperature 57 degrees Fah. on the 



*It is often the case that a school of mackerel may be kept alongside of the vessel 

 for many hours at a time, even during the hottest days of summer, though generally 

 at such times they will not bite very much. For this reason, therefore, the fishermen 

 do not usually endeavor to keep the fish alongside of their vessels, but prefer instead 

 to change their position and try to secure a new school of mackerel. This action on 

 the part of the fishermen, just referred to, may have led to the belief that their move- 

 ments were caused by the disappearance of the fish from the vessels' side instead of 

 on account of the disinclination of the mackerel to take the hook. — J. W. Collins. 



tHind, Fisheries of British North America. 



t Professor Verrill, page 485, Report of the United States Commissioner of Fish and 

 Fisheries, 1871-'72. 



