294 NATUEAL HISTORY OP AQUATIC ANIMALS. 



other surface feeders swim open-mouthed against the wind. Dr. Brown states that the right 

 whale and most of the whale species feed in a similar manner. The right whale feeding swims 

 leisurely at the rate of about four miles an hour. Mackerel, when feeding, come often by millions, 

 like a swiftly moving ripple on the water, with eager, staring eyes and mouths distended to entrap 

 the floating prey. Many of the free-swimming pteropoda are active only during the night-time, 

 sinking during the day to a certain zone of depth. 



"The effect of currents and tides, assisted by winds, is to drive these free-swimming forms 

 towards the different shores and into land-locked or sheltered bays. On the shores of the open 

 sea a continued land breeze drives them far out to sea, and the fish following them will be lost to 

 view. Off the coast of the United States the Mackerel ground is not unfrequently found near the 

 summer limit of the Gulf Stream where wide-spreading eddies prevail, caused by the meeting of 

 the great Labrador current flowing in an opposite direction, or the surging up of the arctic under- 

 flow. In these vast eddies the temperature is greatly reduced by the mixing of almost ice-cold 

 water from beneath with a warm overlying stratum. 



"It is here, too, that the free-swimming mackerel food will congregate, sometimes at the sur- 

 face, at other times at different depths, dependent upon the temperature of the mixed waters. In 

 the vicinity of the south edge of the Grand Bank of Newfoundland the line of contact between the 

 Arctic and the Gulf Streams is sometimes very marked by the local currents which ' boil and form 

 strong eddies.' The line of contact of the two great cold and warm currents is continually chang- 

 ing for hundreds of miles with the varying seasons, and under the influence of winds ; hence, also, 

 the changes in geographical position and in the depth or zone of the open-sea mackerel grounds.' 



"Inshore the floating and free-swimming food is drifted to and fro by winds and tides, and 

 great accumulations are sometimes thrown up upon the beaches in windrows after storms. This 

 floating and swimming food gathers in eddies, either near the coast line or at the junction of 

 opposing tidal waves or currents. Hence, along sheltered and embayed coasts, confronting the 

 open sea in the vicinity of banks where great tidal currents and eddies are formed, or in the gulf 

 and estuary of the Saint Lawrence, where two opposite and wholly different tides dragging along the 

 coast line approach to meet, there will be the mackerel ground of the fishermen, but not necessarily 

 at the surface." 



The winged pteropods very properly form an important part of the mackerel food, as they 

 sink and rise with changes of the temperature of the zone or sheet of water in which they are 

 feeding. 



Eeprodtjction. — Although little is actually known concerning the spawning habits of the 

 Mackerel compared with those of fish which, like the shad .and the salmon, have been artificially 

 propagated, it is perhaps safe to say that the subject is understood in a general way. The testi- 

 mony of reliable observers among the fishermen of our coast and the coast of the British Provinces 

 indicates that the spawning takes place in rather deep water all along the shore from the eastern 



' There are no mackerel-fisliing grounds ■within 300 miles or more of the Grand Bank, and certainly none nearer 

 than 400 miles of its southern edge. It is possible that mackerel have occasionally been seen, or stray specimens 

 captured, nearer the Grand Bank than this, but no mackerel fishermen would think of trying for these fish east of 

 the west coast of Newfoundland. There are but two instances on record where mackerel fishermen have gone so far 

 east as that. Whatever influence may be exerted upon other forms of ocean life by the meeting of the Gulf Stream 

 and the Arctic Current, it can be quite safely asserted that the Mackerel are never found in summer near the junction 

 of these currents, excepting, perhaps, on the southern edge of George's Bank and off the south shoal of Nantucket. 

 These localities are the nearest mackerel-fishing grounds to the Gulf Stream of any on the United States coast. And 

 even here Mackerel are rarely or never taken nearer' than fifty or sixty miles from the northern edge of the stream.^ 

 J. W. Collins. 



