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Pelagic accumulations of fish are formed above the underwater mountains of the Whale Ridge in the evening and at night, but not observed during daylight hours. The study of such an accumulation above one of the mountains reveals its structure. The central part of the cluster consists of splendid alfonsino Beryx splendens, silver scabbardfish Lepidopus caudatus and oilfish Ruvettus pretiosus tend to keep on the periphery of the splendid alfonsino accumulation . Previously, it was found that food of splendid alfonsino, silver scabbardfish, rosefish Helicolenus mouchezi, Richardson’s boarfish Pentaceros richardsoni, and Cape bonnetmouth Emmelichthys nitidus consisted of organisms forming sound-scattering layers (SSL) above the underwater mountains. The composition of food and the daily dynamics of feeding of the listed commercial fish species indicate that they use two feeding tactics. In the first case, rosefish, Richardson’s boarfish, and Cape bonnetmouth forage for most of their food during the day at the bottom, when the SSL-forming organisms descend to the top of the underwater mountain during the diel migration. In the second case, splendid alfonsino, silver scabbardfish, and oilfish as part of a structured pelagic aggregation feed at night on the organisms rising into the upper layers of the water and forming sound-scattering layers. This tactic expands the possibilities for feeding fish that form pelagic aggregations in the dark hours of the day and allows the use of organisms both brought by the current to the mountain top and those that descended here earlier during the diel migration and then stayed until the beginning of the evening.

The feeding characteristics of rosefish Helicolenus mouchezi , pelagic armourhead Pentaceros richardsoni , and the Cape bonnetmouth Emmelichthys nitidus nitidus inhabiting the Valdivia Seamount (central part of the Walvis Ridge) have been studied. In the daytime, these fish form schoolings at the top of an underwater rise; the organisms of the macroplankton, pyrosome Pyrosoma atlanticum and the appendicular Fritillaria sp., form the basis of their food spectra. These macroplankton species descend down to the sea bottom during the diel vertical migration of organisms that form the sound scattering layers. Bottom organisms are found in small numbers in the food spectrum of rosefish only. At night, when the organisms of the sound scattering layers migrate to the surface, the schoolings of the studied fish species at the summit of the seamount disintegrate, their feeding intensity decreases, or they stop feeding at all.