Pelagic Zone

The pelagic zone is divided by depth: epipelagic (0–200 m, photic zone), mesopelagic (200–1,000 m, twilight zone), bathypelagic (1,000–4,000 m), abyssopelagic (4,000–6,000 m), and hadopelagic (below 6,000 m). Pelagic fish are typically streamlined, silver-sided (countershading), and lack a benthic anchor. The mesopelagic zone hosts the greatest biomass on Earth — dominated by lanternfish and bristlemouths performing the largest daily vertical migration on the planet, ascending to feed at the surface at night and descending to avoid predators by day. This biological pump transfers enormous amounts of carbon to the deep ocean.