How do deep-sea protacanthopterygian fishes survive where food is scarce?

Deep-sea protacanthopterygian fishes survive in food-poor environments through several biological adaptations that minimize energy expenditure and maximize resource acquisition.1

• Reduced Energy Requirements: The bodies of typical oceanic protacanthopterygians are feebly developed and appear to consist of little more than gelatinous material. Because their skeletons and muscles are reduced, they require very little energy to maintain their bodies.1
• Nightly Migrations: Many deep-sea species perform nightly migrations to the food-rich surface zone to feed, allowing them to exploit resources produced in the sunlit upper layers of the ocean.1
• Benthic Feeding: Species that inhabit the deepest parts of the ocean rely on food that filters down from above. This organic matter becomes concentrated in the ocean’s thin bottom layer, or benthic zone, which allows benthic fish species to maintain a relatively high abundance despite the scarcity of food in the water column.1

These strategies allow these fishes to maintain numerical abundance in an environment where primary food production is limited to the upper layers of the ocean.1