Bottom-dweller fish, also called bottom feeders, are fish that live and feed on or near the bottom of the sea. Scientists refer to these animals using many different names, most names making reference to benthos (the word for the flora and fauna found on the sea or lake bottom or in the sediments of the bottom), calling them groundfish, benthic or benthopelagic fish. The most common examples of bottom dwelling fish are Dragonets, Hawkfish, Sandperches, Lizardfish, Sand Divers, Jawfish, Flatheads, Velvetfish, Flounders and Soles, but some species of sharks also prefer the safety offered by the sea bottom.
Bottom dwelling fish species prefer water beds with a sandy or muddy substrate, usually areas with a maximum depth of around 200 m, where sunshine can still penetrate the water, at least to a certain extent. In coastal areas, they can be found mainly in the immediate proximity of continental slopes. They don’t like deep waters, but they appear around islands where the water is sufficiently shallow.
Many bottom dwelling species are detrivores, which means that they obtain the nutrients they need by consuming the detritus, that is, the plant and animal particles, including the feces decomposing on the bottom of the water. However, there are many bottom-dweller fish that feed on other species living on the bottom of the sea, which makes them carnivorous. Whether carnivorous or detrivores, all bottom dwelling species need a method to cope with the inedible particles they swallow with their food such as sand, that is why all of them are able to pump out indigestible sand through their gill slit.
The body of bottom feeding fish has adapted to the special circumstances they live in. Most species are flat-bodied in order to give the animals more stability while resting on the bottom of the water. Some species, such as stingrays or flatfish, are even able to bury themselves in the substrate, making them not only comfortable in the sand, but also invisible and safe. Some bottom-dwellers have adapted so well to having to obtain their food from the substrate that they even have mouths that point downwards, towards the place where food comes from, while others, notably carnivorous bottom-dweller species such as stargazers have mouths that point upward, enabling them to catch prey swimming above them while they are resting comfortably on the sea bed.
Some bottom-dwelling species such as stingrays, stonefish and some species of velvetfish have more than their body shape to rely on for protection – they are also able to release venom, mostly neurotoxins of various potency, numbing, paralyzing or just causing pain to their predators.
Bottom-dwelling fish species show considerable diversity in terms of the propagation method chosen. Some of them, such as the jaw fish, are mouthbrooders, which means that the females keep their young in their mouth for a while after they hatch to protect them from predators, while others are known to release their eggs, which flow freely until hatching.