Most of these fish have eggs that float up and develop in surface waters. The bathypelagic-mesopelagic fish Cyclothone may be the most abundant vertebrate on earth. It is small, nondescript, and nobody knows why it is so abundant. Marine mammals Marine mammals are related to land mammals. Baleen whales are filter feeders, taking in huge amounts of water and filtering it forward by pushing with the tongue, skimming off the zooplankton and small nekton.
Gray whales feed on the bottom, filtering small benthos out of the sediments.
Many of these whales undergo extensive migrations - e.g. humpbacks spend winter in HI and summer in AK waters, and gray whales migrate between Baja and Alaska. Whaling has long had a major effect on whale populations, and some were nearly driven to extinction, particularly after the advent of factory ships and harpoon guns. This harvest has been mainly stopped, but not all the whales seem to be recovering. Dolphins and porpoises are rapid swimmers that often form huge pods. They hunt prey by using sonar primarily.