NO. 9 MARINE INVERTEBRATES, ALASKA — MacGINITIE 187 



few, if any, walruses are taken. They feed on clams and perhaps to 

 some extent on sausage worms (EcJiiurus echiurus alaskanus) . 



Of least economic value is the polar bear, for it is not prized as 

 food by the natives. The skin is used, though not to the extent that 

 sealskin is. The polar bear is afraid of nothing, for no animal of the 

 Arctic except man is likely to injure it, and the chance of its encoun- 

 tering man in the vast expanse of ice over which it roams is remote. 

 When a hunter is sighted, the bears will walk right up to him to 

 investigate, and Eskimos often let them come as close as 25 or 30 feet 

 before shooting them. Polar bears feed almost exclusively on the two 

 seals mentioned above. They are usually infested with Trichinella 

 worms, but from what source is not definitely known. 



Before leaving the subject of marine mammals, mention should 

 be made of the use of their skins, which supply certain special needs 

 of the natives. (Caribou is the most widely used for clothing, and 

 wolverine fur, which is unique in that it does not allow the breath to 

 freeze on it, is often used to border parka hoods.) 



Skins of the bearded seal are used for many purposes, especially 

 for making soles for mukluks, covering boat frames, and making 

 thongs to be used as ropes and cords. Skins of the little harbor seal 

 are made into air floats that are attached to harpoon lines for float- 

 ing whales so they can be located after they have died. Walrus skins 

 are also utilized in various ways. 



All these marine mammals, upon which the Eskimos are so de- 

 pendent for food, clothing, and implements, are in turn dependent, 

 either directly or indirectly (but largely directly), upon the marine 

 invertebrates for food. 



DISCUSSION 



It is the practice in many ecological investigations to count every 

 animal in every haul and give the total weight of each species. From 

 the results the "dominant" animal is selected and the animals to be 

 found at certain depths are listed. This is very time-consuming, and 

 the results do not justify the amount of time spent. 



There are many factors in addition to the type of bottom and the 

 depth that determine the number of animals taken in any one dredge 

 haul. Some, such as certain snails and ophiurans, congregate for mat- 

 ing, and a dredge haul through a congregation of such animals would 

 give an entirely erroneous idea of the "dominant" animal in that lo- 

 cality. Others, such as certain sea urchins, habitually move about over 

 the ocean bottom in colonies, and might be at one place one day and 

 at another several weeks later. Sometimes an animal is vastly de- 



