THE SEA FISHERIES OF EASTERN NORTH AMERICA. 57 



The capture during the summer and autumn of fishes of the south- 

 ern coast as far east as Long Island Sound, Vineyard Sound, and Buz- 

 zard's Bay, is not a matter of surprise. . 



The influence of temperature upon the movements of fishes, as al- 

 ready stated, is seen both in different parts of the coast and at differ- 

 ent altitudes in the same region. 



Oceanic currents also have more or less influence upon the distribu- 

 tion of fishes. This, however, depends more upon the pursuit by them 

 of the less independent algae, jelly-fish, crustaceans, ascidians, &c, that 

 float hither arid thither with the tide. 



The apparent clearness of the water is also a factor in this consider- 

 ation, various species preferring one extreme or the other, and coming 

 inshore or near the surface with this variation. 



The temperature of the atmosphere probably influences the move- 

 ments of fish only so far as it affects the temperature of the water itself, 

 the surface strata being, of course, heated or cooled very readily with 

 variation of the air in this respect. The clearness of the sky and the 

 consequent amount of light has a very decided influence on some fishes, 

 especially the pelagic species, invertebrates too being affected in a sim- 

 ilar manner. A bright sunny day will frequently call up forms that 

 are never seen at any other time, while others again only approach 

 the surface on cloudy days or even in the night exclusively. The action 

 of the winds of the ocean is also to be considered in this connection, al- 

 though possibly more is due to local currents as affecting the water 

 than anything else. It is not impossible that variation in temperature 

 may have great influence upon some fishes provided with air-bladders, 

 by which the depth of immersion can be conveniently graduated. 



In what way the influeuce of aerial currents or winds are felt by fish 

 is difficult to say. Von Frieden, however, as the result of a comparison 

 between the actual catches of herring by the German fishermen and the 

 records of the corresponding days and hours, has come to the conclu- 

 sion (Circulaire des Deutschen Fischerei-Vereins, 1874, p. 200) that the 

 best results always followed with the wind from the northwest, and that 

 generally northern winds were better than southern, and western bet- 

 ter than eastern. 



The reproductive instinct.— It is under the stimulus of the re- 

 productive instinct that many of the more notable movements of fish 

 take place, although by what prescience they are enabled to understand 

 that the interests of their progeny require a change of abode, and es- 

 pecially from salt water to fresh, it is, of course, impossible to explain. 

 The anadromous movements, or the ascent of rivers by salmon, shad, 

 and fresh- water herring, &c, all in countless myriads, and with almost 

 unerring regularity, are notable examples. It was formerly supposed 

 that these fish moved in great bodies along our coast, sending off de- 

 tachments into the mouths of the rivers as they went by. The more 

 rational hypothesis now is that they live -in the deeper waters of the sea 



