(750) m is an intermediate layer without clear domination of representa- 

 tives of any one feeding group. At depths from 750-1000 m to 3000 m in 

 the tropics, zoophages play a significant, usually dominant, role. 

 Deeper, euryphages dominate. 



Basic trophic complexes of macroplankton and nekton at various depths . 

 The vertical zones of the oceanic pelagic zone correspond to the trophic 

 complexes of macroplanktonic and nektonic organisms occupying the higher 

 levels of the food chain (Parin, 1970, 1971; Borodulina, 1974). 



The epipelaqic complex consists of (holoepipelagic) crustaceans, 

 constantly inhabiting this biotope (euphausi ids , less frequently shrimp), 

 cephalopods, fish, sea snakes and chelonia and many whales, as well as 

 the interzonal animals which rise to the surface at night to feed (nycto- 

 epipelagic species). The second level predator niche here is occupied 

 primarily by macroplanktonic organisms and relatively small fish (in the 

 higher latitudes, until recently baleen whales were extremely important); 

 at higher levels, only nekton are represented (large fish, dolphins, etc.). 



An independent trophic complex can be distinguished in the tropical 

 area in the boundary layer between the epipelagic and mesopelagic zone, 

 at a depth of 100-300 m. This complex combines second and third level 

 planktophages, constantly present at these depths (certain euphausiids 

 and hyperiids, juvenile squids and fish, mature fish from the families 

 Sternoptychidae, Scopelarchidae, etc.) or numerous euphausiids, shrimp 

 and myctophids, migrating here at night from the mesopelagic zone to 

 feed. All these animals, including the interzonal migrants, serve as 

 food for such nektonic predators as fish from the families Paralepididae, 

 Bramidae, Gempylidae and a number of species of squid from the families 

 Ommastrephidae and Onychoteuthidae, which are themselves eaten by the 

 alepisaurs, large ("level") tuna and marlins, sharks and bottlenose 

 whales (but not'the sperm whale). All of these, except for the alepisaurs, 

 are genetically related to the epipelagic area (which is indicated in 

 particular by the fact that smaller species of tuna and the juveniles 

 of larger tuna and marlins inhabit the surface levels), and their departure 

 from the upper layers is energetically justified by the richer food avail- 

 able in the boundary area between the epipelagic and mesopelagic biotopes. 

 The epipelagic and interzonal organisms rarely form a part of the food of 

 these predators (Fig. 5), since they feed in this layer during the daylight. 



In the mesopelagic zone itself, coexist two trophic complexes--the 

 stable complex, consisting of nonmigrating or short-range migrating animals, 

 and the migrating ("strata!") complex, including organisms which perform 

 daily vertical movements as a part of the migrating sonic scattering 

 layers (SSL). Both complexes consist primarily of macroplanktonic (or 

 micronektonic) crustaceans, cephalopods and fish, primarily third or fourth 

 level predators; the true nektons are very scarce in the mesopelagic zone, 

 the most important of them being the sperm whales, which feed in this layer. 



The special trophic complexes of the deep layers of the oceanic pelagic 

 zone--the bathypelagic and abyssopelagic zones--are combined by their 



46 



