INVERTEBRATES AND FISHES 

 COLLECTED IN THE ALEUTIANS 



1936-38 



By Victor B. Scheffer, Biologist 



Introduction 



In the expeditions to the Aleutian Islands conducted by the 

 Fish and Wildlife Service from 1936 to 1938, chief emphasis was 

 placed on investigations of birds and mammals. Limited studies 

 were made of the lesser forms of animal life that inhabit the sub- 

 arctic waters of the Northeast Pacific and the Bering Sea and 

 that live on the shores and slopes of the islands. With relation 

 to the birds and the mammals, the myriad lesser organisms may 

 collectively be termed the "supporting fauna." 



One must actually visit the northern seas to realize the abun- 

 dance of small animal life in the water and along the shore — 

 abundance not of kinds but of numbers. From the deck of a ship, 

 it is often possible to see swarms of reddish microcrustaceans 

 drifting along on the surface of the water in such profusion that 

 they impart a reddish cast to the water. At night, the churn 

 of the ship's propeller sometimes turns up a glowing wake as it 

 brings countless bodies of luminescent organisms to the surface. 

 These organisms are recovered in the stomachs and crops of 

 auklets and petrels. Where the ocean currents cause an upwell- 

 ing of water rich in plankton, shearwaters and fulmars flock to 

 the scene and baleen whales soon appear. On one occasion, at 

 Unimak Pass, it was estimated that the surface of the ocean for 

 15 square miles was covered with feeding shearwaters, each sepa- 

 rated from its neighbor by 10 or 20 feet. If the carcass of a 

 bird or fish, weighing about 5 pounds, is lowered to the bottom 

 of the sea and hauled up on the following day, the bones usually 

 will have been picked clean by small amphipod crustaceans. 



On certain of the Aleutian beaches that are covered with flat, 

 shingly rocks the size of a man's hand, it is possible to uncover 

 as much as a half pint of amphipod crustaceans or sand fleas hid- 

 ing beneath a single rock. Such organisms, on islands with ex- 



365 



