Fish are found in almost every marine environment, from the deepest ocean trenches to mountain streams high above the sea level. They have been used as a major source of food since the beginning of recorded history.
Traditionally, extant fish species are divided into three classes. These are Agnatha (jawless fish), Osteichthyes (boneless fish), and Chondrichthyes (cartilaginous).
About 33,600 different species of fish are known. No other vertebrate group show such species diversity. However, a far more detailed scheme also exits. Since it’s impossible to pin down all, we have made a list of 12 most common fish species on Earth.
12. Siamese Fighting Fish
A Siamese Fighting Fish | Image Courtesy: Daniella Vereeken/Flickr
Scientific Name: Betta splendens
Conservation Status: Vulnerable
The Siamese fighting fish, commonly known as the betta, is a common sight in aquariums around the world. Though betta specimens in aquariums often exhibit vibrant colors, they are usually dull brown and grey in appearance. On average, a Betta measures about 6.5 cm in length.
Bettas are territorially aggressive species. Both male and female bettas show a high level of aggression against each other, especially when confined to a small area. The species is native to Mainland Southeast Asian countries including, Thailand, Laos, Cambodia, and Vietnam.
A common goldfish
Scientific Name: Carassius auratus
The goldfish is perhaps the most common aquarium fish in the world. If you have or ever had an aquarium, there is a big chance that you kept a goldfish as a pet.
Based on bodily characteristics and coloring, goldfish can be classified into 300 varieties. Most of the well-known goldfish varieties originated from China, where they were selectively bred for the first time about 1,000 years ago.
Carassius auratus is also one of the most well studied freshwater fish species. Multiple research has shown that goldfish have powerful cognitive and learning abilities. In one such study, researchers found that goldfish can differentiate between different colors and shapes. They also have a memory span of three months.
10. Wels Catfish
A wels catfish near Leipzig, Germany | Image Courtesy: Dieter Florian
Scientific Name: Silurus glanis
Lifespan: 50 Years
Wels catfish, sometimes called sheatfish, is one of the extant species of catfish found in slow-flowing rivers and lakes around the Eurasian region. A small number of wels catfish live in Chernobyl’s long-abandoned cooling ponds. Surprisingly, they appear to be somehow unaffected by radiation.
At its full extent, a wels catfish can measure up to 5 m in length and 300 kg in weight. It is the largest freshwater fish found in Eurasia. Large wels catfish (above 15 kg) are a popular target for sport fishing due to their aggressive nature.
A swordfish on deck | Image Courtesy: NOAA
Scientific Name: Xiphias gladius
Lifespan: 9 Years
Swordfish are recognized by their long, pointed beak or bill (rostrum). As a migrant species, swordfish are widely found in tropical as well as temperate regions of the world. They are known for their speed and agility, which allows them to catch prey more efficiently.
The largest swordfish, on record, measures about 4.5 meters in length and 650 kg in weight.
Like few shark species, swordfish depends on the environment to regulate their body temperature. A specialized heating organ helps them raise the temperature to 15 degrees in tissues located around their eyes. Out of 25,000 species of bony fishes, Swordfish is one of the only 22 species that possess such heating mechanism.
8. Atlantic Cod
A female Atlantic cod in captivity | Image Courtesy: Bruce McAdam/ Wikimedia Commons
Scientific Name: Gadus morhua
Lifespan: 25 Years
The Atlantic cod, or simply cod, is among the most consumed fish (by humans) in the world. They are found on both sides North Atlantic Ocean as well as parts of the Arctic Ocean including the North Sea and Baltic Sea.
The species can be recognized by a notable white stripe that runs along its lateral line and dark spots on the upper body. An average Atlantic cod measures about 1.2 meters in length and 40 kg in weight. The largest known cod on record, however, weighed about 96 kg.
The Atlantic cod population registered a steep decline in the 1990s, due to its overfishing in the latter half of the 20th century, and it is still unable to fully recover.
7. Atlantic Mackerel
Atlantic mackerel | Image Courtesy: Petar Milošević CC BY-SA 4.0
Scientific Name: Scomber scombrus
The Atlantic mackerel is known by many names such as Scottish mackerel, Boston mackerel or just mackerel. They are commonly found in temperate waters of the North Atlantic ocean. A mature Atlantic mackerel can grow up to 30 cm in length, however, the largest spotted specimen was about 60 cm long.
During a spawning season, a female Atlantic mackerel can produce as much as 450,000 eggs. Every year, about one million tonnes of Atlantic mackerel are caught by fisheries.
One of the reasons why the species is in such high demand is because it is extremely rich in vital nutrients such as vitamin b, selenium, and Omega 3 fatty acid.
6. Neon Tetra
A Neon Tetra | Image Courtesy: Holger Krisp/Wikimedia Commons
Scientific Name: Paracheirodon innesi
Lifespan: 5-10 Years
The neon tetra is a popular aquarium fish, known for its vibrant color pattern. They are native to both clearwater and blackwater streams in the Amazon basin but are also available in various Southeast Asian countries where they are farm-grown. The maximum length of a neon tetra is about 3.5 cm.
The species can be easily distinguished by two iridescent horizontal stripes on each side. The first is a shiny blue stripe that extends from its eye to adipose fin. The second one is a thick red stripe that originates from the middle of the body and ends near the back of its tail. These iridescent stripes become dull or grey at night.
5. Common Carp
A wild common carp | Image Courtesy: Wikimedia Commons
Scientific Name: Cyprinus carpio
The common carp is a popular type of fish, used both as a food and in sport. Though common carp is native to Asia and Europe, it has been successfully introduced in other regions of the world.
There is a striking difference in shape and size between domesticated and wild common carp. The domesticated ones tend to be bulky and larger sometimes as much as 4 times the wild common carps. The largest known specimen of the species weighed around 45 kg.
In a year, a single female common carp can lay close to one million eggs but only a few survive as they fall victim to a wide range of fungal and bacterial infections. Common carp are known to interbreed with goldfish.
Despite its popularity as fish food, the common carp is recognized as a pest in some parts of the world due to its highly destructive and invasive nature. In Australia, authorities are working on a few methods that would restrict their explosively growing population.
Scientific Name: Pangasius bocourti
Basa is a widely consumed (by humans) fish species found mostly in mainland Southeast Asia. Regionally, the species is known by different names. In the UK, they are popularly known as “river cobbler”, while in Australia, they are called basa fish or swai.
In North America, the basa (from its native region) is mostly avoided. Environmental Research organizations like OceanWise, a part of the Vancouver Aquarium, have raised concerns about the potentially negative impact of basa on its immediate environment.
Various aquariums in the United States and Canada recommend hobbyists to avoid basa fish among other species.
3. Nile Tilapia
A Nile Tilapia | Image Courtesy: Wikimedia Commons
Scientific Name: Oreochromis niloticus
Nile tilapia is among the most important food fishes in the world. The species is native to northern Africa, though populations of Nile tilapia have been introduced in various other parts of the world. A Nile tilapia averages about 60 cm in length and rarely exceeds 5 kg in weight.
It appears, from various paintings, that the species was well known to the Ancient Egyptians. One such illustration is found on ancient Egyptian tomb depicting fish, most possibly tilapia, in a man-made pond.
Nile tilapias are highly social. They even exhibit social hierarchies, where males are more dominant and usually have control over mating and food.
A brown trout | Image Courtesy: U.S Fish and Wildlife Service
Trout is a common name used to acknowledge a wide number of freshwater fish species that belong to three different genera; namely Salmo and Salvelinus, and Oncorhynchus.
Patterns and coloration on trouts can vary based on their immediate environment, and many of its species exhibits intense coloration when they are about to breed. Apart from a few, all trout species are morphologically different from each other but show no signs of major genetic differences.
Lake trout, which is widely popular in North America, can weigh more than 30 kg.
A cherry hybrid salmon | Image Courtesy: Wikimedia Commons
Like trout, salmon is a member of the family Salmonidae. There are about nine species of salmon, all of which come from two different genera. Few other fish species are called salmon in different parts of the world but are not salmon (for example, Australian salmon and Hawaiian salmon).
Today, salmon species are farmed extensively in different regions of the world but they are native to the Atlantic and Pacific oceans. Most of the salmon species are anadromous; a migration pattern in which fish migrate from ocean up onto freshwater to hatch or spawn.
It is a popular belief that anadromous salmon returns to the exact same spot where they hatched. Tracking and behavioral studies have shown this to be true for the most part.