DEEP-SEA FISHES 393 



The deep-sea fishes thus comprise two distinct faunas; and the dis- 

 tinction is emphasized by an actual separation. The bathypelagic zone 

 begins at a depth of about 200 meters where the pelagic zone — which is, 

 so to say, an extension of the layer of water overlying the continental 

 shelf — leaves off. Its lower limit is not so definite, but it is probably at 

 about 2000 meters, and assuredly stops far short of the ocean floor. 

 Between the bathypelagic and abyssal zones lies a thick intermediate 

 mass of water in which only occasional wanderers occur. Though the 

 oceans of the globe contain about 302,000,000 cubic miles of water, 

 really only a little of this enormous space is inhabited. The sea truly 

 teems with fish only at the shore and in the waters over the continental 

 shelves, where such bottom-loving forms as the cod abound. 



The deep-sea environment is the closest approach to nirvana that the 

 earth provides. Below the 200-meter line, which roughly marks the edge 

 of the continental shelf and the limit of the pelagic zone, the seasons 

 cease to exist. Below 400 meters, there are no days — only perpetual night. 

 No plants can grow there, and so it is dog-eat-dog — or dog-eat-carrion, 

 for a considerable part of the food of deep-sea fishes consists of a ghastly 

 rain of invertebrate corpses and vertebrate fragments, drifting down to 

 them from above. 



The currents in the deep waters are nowhere rapid, and toward the 

 bottom the water is quite stagnant over much of the ocean floor — only 

 the slow Antarctic drift has an influence so far down. The constancy of 

 deep-sea conditions is reflected in the homogeneity of the fauna, for 

 about the same assortment of bathypelagic species lives in one ocean as 

 in another. Only in such enclosed holes as the Sulu Sea, and in the 

 Mediterranean, have local, unique faunas developed. 



The striking features of the bathic environment are the high water 

 pressure, the low temperature, and the absence of light. Of these, tem- 

 perature, more than anything else, rules the lives of the deep-sea fishes. 

 Over about half of the total area of the oceans, the bottom temperature 

 stands between 35° and 40° Fahrenheit. At depths of 1000 meters or 

 more, it is usually at the freezing point of fresh water. Near the poles,, 

 the upper layers of water are extremely cold, but are succeeded by 

 warmer layers beneath them, and these in turn by the paralyzing cold of 

 the abyssal drifts. The great 'deeps', scattered here and there over the 

 globe to the number of about fifty, are well below freezing. Some of them 

 sound more than six miles, and their waters remain liquid because of the 

 tremendous pressure. 



