Fish Biology and Behaviour

The Differnt Forms and shape of Fish

As evolution past through today there are many different shapes and forms of fish that can be found. Each with its abdaptaions which provides ach fish the tools for thier specilised habits and to embrace each habitat. Below is a list and information about different fish shapes.


Fusiform is the most common shape in fish species. This body shape makes the fish hydromatic Which means the fish is very streamlined in water, so the fish with this shape can swim fast in open water. For example the Greater Amberjack Seriola dumerili which is amember of the tuna familly: Carangidae has a fusiform shape. It swims in fast open water so that it can catch shoaling fish such as mackeral or sardines, the Greater Amberjack has also a lunate shaped caudal fin. The Lunate caudal fin is a rigid fin with less suface area whick means that there is less drag so that the fish can have great acceleration. Greater Amberjacks are shoaling fish which enables them to spear head on larger shoals of smaller fish such as sardines and cause confusion in their behaviour


Fish with a flat body such as plaice are known as Depresseform. here are many varieties of fish that are a depressifiom shape such as skates, rays, and flat fish. fis like plaice and soles generally have camoflage atern to blend in the substrate, either to hide from predators or to abush prey items. manta rays are a sepessiform on a large scale. This makes it easier to travel long lond distances buy just gliding in the water where currents are strong such as the gulf strea. Manta Rays follow the currents to find the richest plankton grounds.


Filiform fish have slender bodies with a larger head dor camouflage thenselves into seaweeds for example pipefish. Also this bodyshape alows the fish to dart throught the water at ease. The Pipefish lives amongst seaweeds and corals and merge themselves in the seaweed to hide from pradators. Pipefish feed on zoo Plankton and coral larvae.


Aquilliform Fish are eel shaped in which they are elongated in which enables them to hide in holes in the sea bed from sunken ships, coral reefs and cliffs walls. As for the European Eel Anguilla anguilla are able to cross land to reach their feedin grounds and to migrate to their breeding grounds using a snake like motion. The European Eel can be found in many freshwater pools and rivers reaching place far from a river body since their ability to breeth air. They body shape of anguilliforms are extremely flexable and move and swim snake like.


Sagittiform fish are arrow shaped with the dorsal fin near the caudal fin which enable fish to lunge at prey. This form is usually found in predator fish like pike and killifish. With pike tend to rivers and ponds and near weed so that they can ambush their prey often taking large fish and shoaling fish. The markings on pike make them camourflaged in reedbeds which helps with ambushing prey.


Fish with compressed shapes have flat, vertical bodies, with one eye on each side. They swim upright and can be very thin. They usually live in reefs where their flat bodies can slip in and out among the corals, sponges, and rocks, keeping hidden from predators. Angelfish, surgeonfish, and butterflyfish are all compressed fish.


A leptocephalus (meaning "slim head") is the flat and transparent larva of the eel, marine eels, and other members of the Superorder Elopomorpha. Fishes with a leptocephalus larva stage include the most familiar eels such as the conger, moray eel, and garden eel, and the freshwater eels of the family Anguillidae, plus more than 10 other families of lesser-known types of marine eels. These are all true eels of the order Anguilliformes. The fishes of the other four traditional orders of elopomorph fishes that have this type of larva are more diverse in their body forms and include the tarpon, bonefish, spiny eel, and pelican eel.

Leptocephali (more than one leptocephalus) all have laterally compressed bodies that contain transparent jelly-like substances on the inside of the body and a thin layer of muscle on the outside. Their body organs are small, and this combination of features results in them being very transparent when they are alive. They also lack red blood cells until they begin to metamorphose into the juvenile glass eel stage when they start to look like eels.

Leptocephali differ from most fish larvae because they grow to much larger sizes (about 60–300 mm and sometimes larger) and have long larval periods of about 3 months to more than a year. They move with typical anguilliform swimming motions and can swim both forwards and backwards. Their food source was difficult to determine because no zooplankton, which are the typical food of fish larvae, were ever seen in their guts. It was recently found though, that they appear to feed on tiny particles floating free in the ocean, which are often referred to as marine snow. Leptocephalus larvae live primarily in the upper 100 meters of the ocean at night, and often a little deeper during the day. Leptocephali are present worldwide in the ocean from southern temperate to tropical latitudes, where adult eels and their close relatives live.

This particular type of fish larva is poorly understood, partly because they are very fragile and eat particulate material instead of zooplankton, plus their good swimming ability enables them to avoid most standard sized plankton nets used by marine biologists. A video recording of a naturally swimming leptocephalus filmed at night off the Island of Hawaii shows an example of their swimming behavior


Elongate, compressed and deep-bodied, ribbon-like, e.g. ribbon fishes, oarfishes


A spherical shape, e.g. in porcupinefish.