110 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [20] 



tion of tlieir food, and the infinite numbers of these forms of life which 

 exist in the sea, from the coast line to a thousand miles from land, may- 

 be inferred from the fact that, together with fish, they form the great 

 staple of food of seals in northern seas. 



" Dr. Eobert Brown states that during the sealing season in Spitz- 

 bergen seas he has taken out of the stomachs of seals various species of 

 Gammarus {G. Sahi7ii ; G.loricatus; G. pinguis : G.dentatusj G. muta- 

 tus, &c.), collectively known to whalers under the name ' mountebank 

 shrimps,' deriving the designation from their peculiar agility in water.* 



" These small crustaceans are found in countless numbers on the great 

 outlying banks off the ISTorth American coast, and in the Labrador seas 

 they are also in great profusion. 



" It is of special importance to notice that very many if not all of 

 these free-swimming creatures in the sea, from invisible microscopic forms 

 to the largest shrimp, sink to different zones of water or rise to the sur- 

 face with the variations in temperature and changes in the direction 

 and force of the wind. In fine weather when the food is at the surface^ 

 the mackerel, the herriug, and 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 feed- 

 ing, 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 entraii the 

 floating prey. Many of the free-swimming Pteropeda 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 unfreauently 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 underflow. 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 surface, 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 str 3ams 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 changing for hun- 

 dreds of miles with the varying seasons and under the influence of winds; 

 * "On the seals of Greenland." — Dr. B. Brown. 



