Nearshore fish, sometimes called
littoral fish, live close to the shore. They are associated with the
intertidal zone, or with
estuaries,
lagoons,
coral reefs,
kelp forests,
seagrass meadows, or rocky or sandy bottoms, usually in shallow waters less than about deep.
Intertidal fish Intertidal fish are fish that move in and out with the
tide in the
intertidal zone of the
seashore, or are found in
rock pools or under rocks. The
intertidal zone of rocky shores can contain indentations which trap pools of salty water, called
rock pools. Living in these habitats are communities of hardy plant and animal species specially adapted for coping with the volatile environment around them. The plants and animals interact with each other and with the rock pool to form miniature
ecosystems, easily accessible to students and a source of fascination for young children. Plants such as
seaweeds, cnidarians such as
sea anemones, arthropods like
barnacles, and
molluscs such as the common
limpet and the
common periwinkle can be permanent residents of rock pools. But most rock pool animals, such as
crabs,
shrimp and fish are just temporary residents, occupying a rock pool only until the next tide takes them to a new location. Some rock pool fish which are temporary residents include the
long-spined sea scorpion, the pipefish worm, the
rock goby and the common
lumpsucker. However some other rock pool fish are territorial in nature, and will stay with the same pool for extended periods. Examples are the
common blenny and its near relative the
butterfish. • The common
blenny, also known as the shanny, is found in northern temperate waters. They hide under rocks and in crannies in rock pools when the tide is out. They feed on green seaweed and invertebrates such as barnacles. They can crawl on dry land, using their paired fins. About long, they have smooth skin, without scales, and are covered with soft slime. The slime prevents them drying if they are stranded on a shore between tides. So long as their skin stays moist, they can breathe out of water. They are sometimes called "sea frogs" because they bask in the sun on weeds outside the water, and like frogs, jump to safety when disturbed. They can change their colour to match their surroundings. The female lays eggs in crevices or under stones and the male guards them until they hatch. In the winter, when storms can be severe, they move out of their rock pools into the shallows. The common blenny is bold with strong teeth, and will bite humans if it feels threatened. • The
rock goby is a small fish, about , found in northern temperate waters. It is coloured black with white blotches, and hides under stones and amongst seaweed. It is a temporary resident of rock pools when the tide is out. The female rock goby lays eggs on the underside of rocks and shells and then leaves them. The male guards the eggs until they hatch. First-year rock gobies often visit rock pools in winter when the older fish have left. File:Australian blenny.jpg|Australian
blenny File:Gobius_paganellus.jpg|
Rock goby File:Long_Spined_Scorpion_Fish.jpg|
Long-spined sea scorpion File:smooth lumpsucker.jpg|Smooth
lumpsucker inflated in a defensive response • The
long-spined sea scorpion, a small stout fish which grows about long, is another temporary resident of rocky pools. They have large black eyes, a large mouth, and four long spines—two on each side on the gill cover—that stick out when the fish is removed from the water. They also have an organ like a finger on each side of their mouths which helps them catch prey. Because of their broad heads, they are also called "bullheads". They have a variety of effective camouflaged colours ranging from shades of browns with cream blotches, to orange and red with white blotches. They can also change their body colour to match their surroundings. They are found around the coasts of Northern Europe in shallow rocky waters hiding amongst seaweed. They are also found in rock pools and sometimes in waters deep. Long-spined sea scorpions lay eggs amongst seaweed or attached to rock crevices. The young hatch after two or three weeks, and go through several development stages before maturing into adults. •
Lumpsuckers are found in temperate northern waters. They live on the seafloor, and are temporary residents of rocky pools in late winter and early spring when they spawn. The body of the lumpsucker is scaleless and covered with small lumps. They have a large sucking disc on their underside which they use to cling to surfaces. They are normally a blue to slate-grey colour, and are effectively camouflaged to look like stones. They are portly, nearly spherical, poor swimmers, reaching lengths up to . After the female lumpsucker lays eggs, the male takes over, clamping itself to a rock where it guards the eggs. When they hatch, lumpsuckers look like tiny tadpoles. They remain in shallow water and rock pools, hiding amongst seaweed and rocks, until they grow up.
Estuarine fish of the
Klamath River is a transition zone between a
freshwater river environment and a
saltwater marine environment. Due to
land runoff, river mouths and estuary waters can be turbid and nutrient rich, sometimes to the point of
eutrophication.
Estuaries are partly enclosed coastal bodies of water with one or more
rivers or
streams flowing into them, and with a free connection to the open sea. These
brackish water habitats form a transition zone between river environments and ocean environments, and
ecological successions can form along the way. Estuaries are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries productive natural habitats. Fishes that spend time in
estuaries (or
river mouths) need to be
euryhaline (tolerant to a range of salinities). Estuaries provide an unstable environment for fish, where the salinity changes and the waters are often muddy and turbulent. In warmer climates, estuaries have
mangroves around their edges. At times there may be only a few different fish species present in an estuary, but seasonal migrants, including
eels,
salmonids, and some
forage fish such as
herrings and
sprats increase the
diversity in the estuary. River estuaries form important staging points during the migration of
anadromous and catadromus fish species, such as
salmon and
eels, giving them time to form social groups and to adjust to the changes in salinity. Salmon are anadromous, meaning they live in the sea but ascend rivers to spawn; eels are catadromous, living in rivers and streams, but returning to the sea to breed. Besides the species that migrate through estuaries, there are many other fish that use them as "nursery grounds" for spawning or as places young fish can feed and grow before moving elsewhere. For example,
herring and
plaice are two commercially important species that use the Thames Estuary for this purpose.
Mangrove swamps are associated brackish water habitats. Many, though not all, mangrove swamps fringe estuaries and lagoons where the salinity changes with each tide. Among the most specialised residents of mangrove forests are
mudskippers, fish that forage for food on land, and
archer fish, perch-like fish that "spit" at insects and other small animals living in the trees, knocking them into the water where they can be eaten. Like estuaries, mangrove swamps are important breeding grounds for many fish, with species such as
snappers,
halfbeaks, and
tarpon spawning or maturing among them.
Coral reef fish support flourishing ecosystems,
paradoxically in clear, low nutrient waters, along tropical continental coasts and around volcanic islands.
Coral reef fish are numerous and diverse. In tropical waters, coral reef fish live amongst or in close relation to
coral reefs. Coral reefs form complex
ecosystems with tremendous
biodiversity. Coral reef fish can be particularly colourful and interesting to watch. Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well camouflaged. Reef fish have developed many ingenious specialisations adapted to survival on the reefs. Coral reefs occupy less than one per cent of the surface area of the world oceans, yet they provide a home for 25 per cent of all marine fish species. Coral reefs often depend on other habitats in the surrounding area for the supply of nutrients, such as
seagrass meadows and
mangrove forests. Seagrass and mangroves supply dead plants and animals which are rich in nitrogen and also serve to feed fish and animals from the reef by supplying wood and vegetation. Reefs in turn protect mangroves and seagrass from waves and produce
sediment for the mangroves and seagrass to root in. is an
anthias. They are hermaphrodite, and swim in "harems".
Anthias are members of the family
Serranidae and make up the subfamily Anthiinae. They are widespread in tropical waters. They have been called the "quintessential
reef fish", and make up a sizeable portion of the colourful
fishes seen swarming in
coral reef photography. Anthias are mostly small, peaceful, beautiful and popular as
ornamental fish. They are mainly
zooplankton feeders. Anthias
shoal and school in large numbers, operating more intimate "harems" within the schools. These harems contain a dominant and colourful male, between 2 and 12 females — who operate a hierarchy among themselves — and one or two "subdominant" males, often less brightly coloured and non-territorial. Within the swarm of females, territorial males perform acrobatic U-swim displays and vigorously defend an area of the reef and its associated harem. Anthias are
protogynous hermaphrodites. All anthias are born female; if a dominant male perishes, the largest female of the group will often change into a male to take its place. This may lead to squabbling between the next largest male and the transforming female, whose hormones are now surging with testosterone. This can turn quite vicious in the limited confines of captivity. has a false
eyespot on its sides, which can confuse prey and predators
Butterflyfish are group of about 120 species belonging to the family Chaetodontidaeof Perchiformes. They include
bannerfish and
coralfish. They are widespread on coral reefs. Butterflyfish are mostly between in length. The largest species, the
lined butterflyfish and
saddle butterflyfish, grow to . Many species are brightly coloured and strikingly patterned, though other species are dull in colour. Many have eyespots on their flanks and dark bands across their eyes, not unlike the patterns seen on
butterfly wings. Their deep,
laterally narrow bodies are easily noticed through the profusion of reef life. The conspicuous colouration of butterflyfish may be intended for interspecies communication. Butterflyfish have uninterrupted
dorsal fins with
tail fins that may be rounded or truncated, but are never forked. Generally diurnal and frequenting waters of less than (though some species descend to ), butterflyfish stick to particular home ranges. The
corallivores are especially territorial, forming mated pairs and staking claim to a specific coral head. Contrastingly, the
zooplankton feeders form large conspecific groups. By night butterflyfish hide in reef crevices and exhibit markedly different colouration. Their colouration also makes butterflyfish popular
aquarium fish. However, most species feed on
coral polyps and
sea anemones, which can result in problems for the hobby aquarists.
Clownfish,
anemonefish and
damselfish are among about 360 species classified in the family
Pomacentridae. Most Pomacentrids are associated with coral reefs in the Indo-West Pacific, with a few species occurring in temperate waters. Some species are native to freshwater or brackish
estuarine environments. Most live in shallow water, from , although some species are found below . Most species are specialists, living in specific parts of the reef, such as sandy lagoons, steep reef slopes, or areas exposed to strong wave action. In general, the coral is used as shelter, and many species can only survive in its presence. The bottom-dwelling species are territorial, occupying and defending a portion of the reef, often centred around an area of shelter. By keeping away other species of fish, some pomacentrids encourage the growth of thick mats of algae within their territories, leading to the common name
farmerfish. Different species display a wide range of colours, although some are relatively drab. Pomacentrids are omnivorous or herbivorous, feeding off algae,
plankton, and small bottom-dwelling
crustaceans. A small number eat coral.
Goatfishes are a family Mullidae of about 55 species of perciform fishes, associated worldwide with tropical
reefs. They are typically about 20 cm long, though the
dash-and-dot goatfish, grows to 55 cm. Goatfish are tireless
benthic feeders, possess a pair of long
chemosensory barbels ("whiskers") protruding from their chins resembling a goat's beard. They use these to rifle through the sediments in search of a meal. Like goats, they seek anything edible;
worms,
crustaceans,
molluscs and other small
invertebrates are staples. Many species of goatfish are conspicuously coloured and have the ability to change their colouration depending on their current activity. By day, many form large inactive (non-feeding) schools: these aggregates may contain both conspecifics and heterospecifics. For example, the yellowfin goatfish school with
blue-striped snappers. When they do that, the yellowfins changes its colouration to match that of the snapper. By night the schools disperse and individual goatfish head their separate ways to loot the sands. The diurnal
goldsaddle goatfish changes from a lemon-yellow to a pale cream when feeding. Other nocturnal feeders will shadow the active goatfish, waiting patiently for overlooked morsels. Goatfish stay within the shallows, going no deeper than about 110 metres. Most species do not tolerate
brackish water, so they do not enter
estuaries or the mouths of
rivers.
Other nearshore fish s can provide shelter and food for shallow water fish Other nearshore or shallow water fish live near the shore in depths of less than 10 metres. They occupy the areas over sandy or rocky bottoms, and can be associated with
seagrass meadows and
kelp forests. They can be divided into
demersal fish and
pelagic fish. Demersal fish live on or near the sea floor, while pelagic fish live in the
water column away the sea floor. Examples of such shallow water demersal fish, found in both tropical and temperate waters around the world, are seahorses, triplefins, wrasse and flounder. As demersal fish, all these fish spend most of their time on or near the sea floor. •
Flatfish are superbly adapted
groundfish, found on muddy and sandy sea floors. In many species both eyes lie on one side of the head, one or the other migrating through and around the head during development. Some species face their "left" side upward, some face their "right" side upward, and others face either side upward. Some flatfish can camouflage themselves on the ocean floor. •
Wrasse are a large family of mainly small fish, usually less than long. Most wrasse are loners that prefer habitats such as coral reefs and rocky shores. They live close to the substrate, eating small invertebrates and almost anything else that lurks on the bottom. Many are brightly coloured. They have thick lips and use their sharp teeth to pick small creatures off the rocks. Many smaller wrasses follow the feeding trails of larger fish, picking up invertebrates disturbed by their passing. •
Triplefins are a
family of fish. They are usually found around
coral reefs and rocks, usually in shallow, clear sunlit waters such as lagoons and seaward reefs. Triplefins have three
dorsal fins (hence the name). They are small fish, usually less than six cm long. Brightly coloured, often for reasons of camouflage, they are nervous and retreat to rock crevices at any perceived threat. •
Seahorses are a
genus of fish. They prefer sheltered harbours, estuaries and other shallow coastal waters, where they hunt tiny crustaceans. They bob around in sheltered areas such as
coral reefs,
mangrove stands and
seagrass meadows and
estuaries. They are camouflaged with murky patterns that blend into kelp and sea grass backgrounds. During social moments or in unusual surroundings, seahorses can turn on bright colours. File:Hippocampus.jpg|Seahorse File:Pseudopleuronectes americanus.jpg|Flatfish File:Cleaning station.JPG|Cleaner wrasses working on a
dragon wrasse File:Common triplefin.png|
Common triplefin Examples of shallow water pelagic fish, found in both tropical and temperate waters around the world, are grey mullet, sprats and garfish. As pelagic fish, all these fish spend most of their time living in the
water column away the sea floor. • The
grey mullet are medium size fish, typically about long. They are often caught with
seine nets. • The
garfish is a long, slender fish, looking like a spear, which feeds on seagrass fragments, shrimps and crab larvae. In turn it is preyed on by larger fish and, since it is often near the surface,
cormorants and
gannets. File:Mucep u0.gif|Grey mullet File:Belone belone1.jpg|
Garfish ==Coastal pelagic fish==