Ichthyology

A fish is an aquatic, anamniotic, gill-bearing vertebrate animal with a tough cranium to protect the brain, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. In a break from the long tradition of grouping all fish into a single class (Pisces), modern phylogenetics views fish as a paraphyletic group that includes all vertebrates except tetrapods. In English, the plural of "fish" is fish when referring to individuals an

Sharks are a group of elasmobranch cartilaginous fishes characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the division Selachii and are the sister group to the Batomorphi (rays and skates). Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period (4

Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2025.

FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web. Over time it has "evolved into a dynamic and versatile ecological tool" that is widely cited in scholarly publications.

thumb|300px|An aquascaping|aquascaped freshwater aquarium Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. It is a practice that encompasses the art of maintaining one's own aquatic ecosystem, featuring a lot of variety with various water systems, all of which have their own unique features and requirements. Fishkeeping primarily serves as a token of appreciation and fascination for marine life and the environment that surrounds such, along with other purposes such as the piscicultural fishkeeping industry, serving as a bran

movement of fishes from one water body to another

biological phenomenon of a group of fish staying together for social reasons

Fauna found in deep sea areas

fish that live all or much of their lives in seawater

hypercarnivorous fish that actively prey upon other fish

young fish

living on, in, or near the bottom of the body of salt- or fresh-water they inhabit (eg: cod, flounder, halibut, sole...)

study of the form or morphology of fishes

detection of weak electric fields, via specialized sense organs and brain structures

Fish living in the pelagic zone of ocean or lake waters – being neither close to the bottom nor near the shore

thumb|300px|Leptocephalus larva A leptocephalus (meaning "slim head") is the flat and transparent larva of eels and other members of the superorder Elopomorpha. This is one of the most diverse groups of teleosts, containing 801 species in 4 orders, 24 families, and 156 genera. This group is thought to have arisen in the Cretaceous period over 140 million years ago.

REDIRECT Underwater acoustics

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measurement of various fish characteristics such as length and weight

nest built by some fish- and frog species to contain their eggs

(Positive) Rheotaxis is a form of taxis, or movement in response to stimuli, seen in many aquatic organisms like fish. It generally involves turning to face an oncoming current. In a flowing stream, this behavior leads them to hold their position rather than being swept downstream by the current. Rheotaxis has been noted in zebrafish and other species, and is found in most major aquatic invertebrate groups. This movement is important for animal survival because the positioning of an animal in the water can increase its chance of accessing food and lower the amount of energy it spends, especial

organism that eats the mud at the bottom of bodies of water

fish used as bait to attract predatory fish

intellectual capacity of fish

thumb|upright=1.35| ---- Fish produce many eggs, typically about 1mm across, and usually release them into the open water column

thumb|The orange chromide, (Pseudetroplus maculatus) will feed on eggs Paedophagy (literally meaning the "consumption of children") in its general form is the feeding behaviour of fish or other animals whose diet is partially, or primarily the eggs or larvae of other animals. However, P. H. Greenwood, who was the first to describe paedophagia, defines it to be a feeding behaviour evolved among cichlid fishes.

Lepidophagy is a specialised feeding behaviour in fish that involves eating the scales of other fish. Lepidophagy is widespread, having evolved independently in at least five freshwater families and seven marine families. A related feeding behavior among fish is pterygophagy: feeding on the fins of other fish.

small fish which are preyed on by larger predators for food

fish that is able to leave water for extended periods of time

thumb | right | alt=this image shows a suckermouth catfish ’s odontodes on its pectoral fins. displaying its teeth-like frills. | The frill-like odontodes on a Guyanancistrus longispinis|suckermouth catfish’s [[pectoral fins]] Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings. They consist of a soft pulp cavity surrounded by dentine and covered by a mineralised substance such as enamel, a structure similar to that of teeth. They generally do not have the same function as teeth, and are not replaced the same way teeth are in mos

reproductive physiology of fishes

alt=Designing and maintaining of Aquarium Tank by the Students of College of Agriculture Yandev. Gboko Benue State|thumb|An aquarist in the process of designing a tank for educational purposes. An aquarist is a person who manages aquariums, either professionally or as a hobby. They typically care for aquatic animals, including fish and marine invertebrates. Some may care for aquatic mammals. Aquarists often work at public aquariums. They may also work at nature reserves, zoos, and amusement parks. Some aquarists conduct field research outdoors. In business, aquarists may work at pet stores, as

ways that fish move

Meristics is an area of zoology and botany which relates to counting quantitative features of animals and plants, such as the number of fins or scales in fish. A meristic (countable trait) can be used to describe a particular species, or used to identify an unknown species. Meristic traits are often described in a shorthand notation called a meristic formula.

Histotrophy is a form of matrotrophy exhibited by some live-bearing sharks and rays, in which the developing embryo receives additional nutrition from its mother in the form of uterine secretions, known as histotroph (or "uterine milk"). It is one of the three major modes of elasmobranch reproduction encompassed by "aplacental viviparity", and can be contrasted with yolk-sac viviparity (in which the embryo is solely sustained by yolk) and oophagy (in which the embryo feeds on ova).