THE SEA FISHERIES OF EASTERN NORTH AMERICA. 55 
seasons are caused by the reproductive instinct, by conditions of. tem- 
perature, and by search for food. They are also to a less degree 
affected by the pursuit of predaceous fish and other fellow occupants 
of the ocean and by the action of man. 
_ Temperature of the water—The most important of these agencies is 
probably that of temperature; since while there are certain species 
that appear to be quite insensibkle to considerable variations in this 
respect, the distribution of others is largely dependent upon the degree 
of heat in the water. Certain fishes, such as the cod and herring, are 
to be taken only in cold water, the herring usually at a temperature not 
exceeding 50° to 55°; the cod ata still lower degree. This relation- 
ship has an important bearing upon the herring fisheries; since, when 
the heat of the surface water is above the degree indicated, herring 
are seldom seen; as this decreases they make their appearance. This 
is so well established that now the herring fishery on the coast of Scot- 
land is largely regulated by the temperature observed, and when it is 
decidedly above 55° the herring are not looked for. 
On the coast of the United States there are two well-defined regions, 
one bounded to the south by Cape Cod and the other having this 
boundary as its northeastern limit. A few stragglers may be found 
occasionally on either side; but practically the cape constitutes the 
boundary line. 
As a general rule the winter temperature of the ocean at different 
points along the New England coast is about the same, the surface 
water as well as that at the bottom showing the minimum degree down 
to absolute freezing. During this season, therefore, all the more delicate 
_ fish leave either to go south or off the shore until they find the tempera- 
ture they require; possibly, however, not until they reach the edge of 
the Gulf Stream. The summer temperatures, however, vary extremely, 
and these variations are accompanied by the presence or absence or 
fish of different kinds. On the south side of New England the warmest 
temperatures observed were in Peconic Bay, where, in August, 1874, 
the bottom temperature was from 71° to 725°, the surface temperature 
in one instance being as high as 74°. Here the same southern types of 
marine animals were predominant. 
At Wood’s Holl, in 1873, the mean temperature at the bottom in 
June was 61.7°, and in July 69.59, and in August 70°, or an average 
of 67°. The surface was sometimes a few degrees higher. 
Elsewhere on the south side of New England the bottom temperature 
ranged from 61° to. 65° off the coast of Connecticut, in from 4 to 20 
fathoms; in rather deeper water from 58.5° to 649. Off Cox’s Ledge 
it was 50° at 52 fathoms in August, and off several miles northwest of 
Block Island it was 45.59 at 47 fathoms, this being accompanied by a 
somewhat different fauna. In general, we may say that south of Cape 
Cod, while the inshore surface of the water during midsummer ranges 
from 62° to 70°, at a greater distance outward, up to perhaps fifteen or 
twenty miles, it ranges from 62° to 68°, and that at the bottom, inside 
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