A Brief Introduction
Fish are a vast species that encompass the entire world. They live in every type of water body in every region of the world. Their main enemies are overfishing practices, ecological changes, temperature changes due to climate change, and other harmful human activities like dams and reservoirs. It is essential to respect their habitats and continue to explore underwater for more discoveries.
Fish are among the first vertebrates which came to life on Earth. These creatures hold a basic blueprint for all the different kinds of body structures found on our planet and have evolved into different types of unusual species. If we look at the first record of other species’ evolution from fish, it will go back to 500 million years. Today, there are more than 32,000 known fish species in the world.
The Primary Enemies of Fish
Fish are a vast species of aquatic beings that encompass the whole world. These creatures thrive on all sorts of water bodies in every part of the world. The main enemies of fish are temperature changes because of climate change, ecological changes, overfishing practices, and other harmful activities of humans, such as the construction of reservoirs and damns. We must leave their habitats undisturbed while discovering and exploring the world underwater.
The Main Types of Fish
There are three primary kinds of jawed fish which descend from their jawless ancestors. They are cartilaginous fish, plated skin fish, and bony fish. Almost 84% of all fish species fall under the category of bony fish. One hundred eight of the remaining species known to us are lampreys and hagfish, while the other 970 include rays, sharks, and chimeras. Plated skin fish are now extinct, and we just have lampreys and hagfish from that category today.
Also called broadbills, swordfish are saltwater fish and the only species from the Xiphiidae family. These giant predatory fish migrate during the change of seasons. These famous sports fish usually possess elongated round bodies. They live in tropical and temperate regions of the Atlantic, Pacific and Indian Ocean. Their long ‘sword’ helps in wounding their prey animal for an easy catch and meal. Thanks to their long body structures, swordfish are fast and agile creatures that further help catch prey. They can reach up to a whopping speed of 97 kilometres an hour. They can survive for as many as nine years if they can escape being hunted by humans for food and sport.
Belonging to the Gadidae family, Atlantic codfish are mainly hunted by humans for food. ICUN has labeled them vulnerable due to over-fishing because of human consumption. They come in brown and green colours with spots on their dorsal side. They can survive for 25 years. They live close to the shoreline and main continental shelf; hence, they make for an easy catch for humans. Weighing up to 40 kg, they can be 61 cm-1.2m long.
Pelagic fish are commonly called mackerel, and they come from the Scombridae family. Found in temperate and tropical seas across the globe, mackerels live along the coasts or off-shore. Their bodies have black stripes running vertically, and they migrate in huge schools for scaring away predators. The large mackerel like tuna, dolphins, whales, seabirds, and sharks, as well as the Atlantic cod, often prey upon the small mackerel. All kinds of predators usually attack these perfect forage beings, and even humans capture them for their high content of Omega-3 oil.
Hailing from the Salmonid family, rainbow trout fish lives in the Pacific Ocean in Asia and North America. They prefer cold water and generally come back to the fresh waters for spawning. They have a broad red stripe on the lateral line that is spread from the tail to their gills. Steelheads are the freshwater kinds of rainbow trout, and Washington has these as their official state fish. They usually weigh up to 2.3 kilos, but some breeds can even be 20 kg in weight. Forty-five countries across the globe hunt these fish for food and sport. An introduced population can have adverse effects on the new habitat. Endangered Species Act has listed their breeds as either threatened or endangered.
Belonging to the Salmonidae family, Atlantic salmons are ray-finned fish found in the rives of the North Atlantic, North Pacific Ocean and the northern regions of the Atlantic Ocean. These get hunted for recreational and commercial activities. Salmons are a little territorial in nature and can get aggressive towards each other occasionally. They also form a school at times. These carnivorous fish feed on stoneflies, caddisflies, mayflies and black flies. There has been a reduction in their number due to hunting and habitat destruction. Various conservation efforts are performed for saving the Atlantic salmon from imminent extinction.
These saltwater fish from the Scombridae family have 15 species in total. Their sizes vary from the Atlantic bluefin tuna to the bullet tuna. On average, they can survive for five decades and keep their body temperature higher than the waters around them. These agile predators swim fast because of their sleek and streamlined bodies. They are among the fastest swimming pelagic fish and can move up to 75km per hour. Many of the tuna breeds are nearing extinction because of overfishing, as these are famous game fish.
The Great White Sharks are a more giant mackerel species and live on coastal surface water in Earth’s major oceans. These sharks are famous for their size, and the male of the species are smaller than their female counterparts. They can weigh around 2,000kg and can reach about 6.1m in length. They can live for as long as 70 years and even more in the wild. They take around 26 years for reaching sexual maturity. The rare Killer Whales are the only natural predators of the shark. After popular movies like Jaws portrayed sharks as ‘man-eaters’, humans fear these even though sharks don’t prefer humans as their prey.
Red mullet fish are usually found in the Black Sea, the Mediterranean Sea and the eastern North Atlantic Oceans. The demersal fish scours and scavenges the seabed in search of small lobsters, crabs, marine worms, shellfish, as well as dead fish for eating. They weigh about 55g and can be 18 inches long. The Mediterranean region loves red mullet as a delicacy, and there are several ways of cooking it. All through history, these fish have been prized, and the Ancient Romans even reared them in ponds.
Generally called the Asian Sea bass, barramundi fish belong to Catadromous species. These are found in the Indo-West Pacific region of Southeast Asia extending to Northern Australia. Barramundi is pretty popular in Thai cuisine, and the locals call these fish ‘pla kapong’. They have a huge mouth, elongated bodies and their upper jaw extends way behind their eyes. Hunted for food and sport, they are found in freshwater and saltwater. They can get 1.8m long and can weigh around 60 kg. These demersal creatures are found in coastal water, rivers, estuaries, and lagoons. They generally swim in clear or turbid water with temperatures ranging from 26 °C to 30 °C.
Commonly called the dolphin fish, mahi-mahi fish dwell close to the waters’ surface and are ray-finned. These are usually found in temperate, tropical and subtropical off-shore waters across the world. They can survive for five years and are carnivorous fish feeding on crabs, mackerel, zooplankton, squid, and flying fish. They belong to the Coryphaenidae family. Their name translates to ‘very strong’ and originates from the Hawaiian language. They possess one long dorsal fin which moves from their head to their tail.
Females have rounded heads while the males sport prominent foreheads. They come in dazzling, vibrant colours of deep greens, bright blues, and golden flecks—their colour changes when they go out of the waters. The golden spots fade into muted yellow-greys when they are about to die.
Anchovies are really tiny foraging fish from the Engraulidae family. These can enter the brackish waters but are usually found in the marine. One anchovy species from South America is restricted only to the freshwaters. These have more than 140 species in the Black Sea, Mediterranean Sea, Pacific Ocean, Indian Ocean and the Atlantic Ocean.
Haddocks are saltwater fish from the Gadidae family. Native to North Atlantic Ocean and its surrounding seas, these are generally bred in northern Europe. Haddocks are essential for the fisheries and are usually sold as fresh, smoked and frozen food. These have an elongated, tapering body which is similar to other codfish. They have small mouths, three dorsal fins and snout-like profiles. These come in a variety of colours like black, brown and dark grey.
Red Seabream Fish
Belonging to the Sparidae family, the red sea bream family, these demersal lives in the subtropical waters with 10-200 metres’ depths. These are mostly found in northeastern regions of the South China Sea. Red seabream fish is regarded as a cuisine in Japan and the Japanese call it madai. They eat madai at essential festivals and events like New Year’s Eve and weddings. On average, they are 54 cm long, but 100.cm is the most oversized length ever recorded. Their diet mainly constitutes of molluscs, worms, crustaceans, echinoderms, along other fish. They are found on shallow seas and reefs.
Gold Line Fish
A seabream fish species, gold line fish, are also called dream fish, cow bream fish, and Salema porgy fish. These fish have very unusual gold stripes running down the lengths of their bodies. These fish are not for commercial consumption as they induce hallucination in people and potentially unsafe. They can leave traumatic and frightening psychedelic effects on humans. The hallucinations take two hours to get induced after the fish consumption and can last for up to 36 hours. Hallucinogenic symptoms are all thanks to their diet, which comprises phytoplankton or particular algae.
Found in North Atlantic regions, Pollack fish is from the Pollachius genus. These fish generally live in the rocky areas of waters, and the juveniles love rock pools. They are also called lythe, saithe, and silver bill. These whitefish can be as long as 105cm, and their weight can reach 21 kg. They have white bellies with greenish-black color on the lateral line. Norway and Britain serve Pollack in a lot of restaurants as their white flesh have a strong flavor. (See How Do Fish Sleep with Their Eyes Open?)
Usually called Mola Mola, ocean sunfish are the heaviest bony fish ever known. They can weigh as much as 1,000 kg. These live in tropical and temperate waters across the world. Ocean sunfish have laterally flattened bodies and feed on sea jellies which are poor in nutrition. So, they eat the sea jellies in large portions for maintaining their mass. A single spawn may have 300,000,000 eggs that are the most eggs among the entire known vertebrate. They have few natural predators, but sharks, sea lions, and killer whales can eat them. People in Japan, Korea, Taiwan, and other regions of the world consider the ocean sunfish a delicacy.
Northern Red Snapper
Native to the Atlantic Ocean, northern red snappers live around shipwrecks and reefs. They have large scales, spiny dorsal fins, laterally compressed bodies and sloped profiles. They also have sharp, needle-like teeth and can live for as many as 100 years. These can be 39 cm long and 38 kg in weight. They are famous for their vivid light red colour with an intense pigment on their back that can fade away with age. They possess 8-9 anal soft rays, 14 dorsal rays, two anal spines and ten dorsal spines.
Bonitos are medium-sized, ray-finned predatory fish from the Scombridae family. They inhabit open waters, which are at least 30m in depth. The Pacific and Atlantic bonito come in a darkish shade, and their meat generally comes in a firm texture with a moderate fat content. People usually eat them baked, grilled as well as pickled. A young or small bonito is generally lighter in colors and is used as an affordable substitute for skipjack tuna at times. Atlantic bonito lives in the Mediterranean Sea and the Black Sea.
These fish feed on other fishes and squid, sand lances, mackerel, silversides, alewives, and menhaden. They weigh around 1.8-2.3 kilos and can be 40-45cm long. Their maximum weight can be 9.4 kilos and 100cm, the full length.
Clownfish belong to the subfamily of Amphiprioninae and are actually known as anemonefish. They are capable of forming symbiotic mutualisms with sea anemones in the wild. They come in shades of yellow, black, red, orange, depending on their species and can also have white patches or bard on the bodies. Native to the cold waters such as the Pacific and the Indian Ocean, clownfish can be 7-16cm in length. Most of these fish are restricted to the smaller areas, but some move towards the larger regions.
Usually, they inhabit the bottom of various sheltered reefs in shallow lagoons or shallow seas. These are protandrous hermaphrodite and can be male or female all through their lives. Clown fish’s number in captivity has hiked after popular films like Finding Nemo and Finding Dory released. In both the movie, the main characters were clownfish.
Native to the Indian Ocean, Pacific Ocean, Hawaii Islands, Austral Islands and the Red Sea, the emperor angelfish is among marine angelfish species. It thrives in wide areas and hence, has a pretty stable population. They are neither reducing in numbers nor under any threat of being extinct. These carnivorous fish feed on sponge algae, small invertebrates, as well as some plants. The female and male generally go to the water surface for mating and spawning. This leads to the eggs being sent along with the currents to various regions across the world.
This lowers the chances of them being eaten by the predators living in the reefs of deep waters. The fish sports an unusual pattern of vibrant designs and colors that makes these a favourite of photographers, artists and aquarists alike. The juvenile emperor angelfish have a dark blue body with blue and white rings. The adults, on the other hand, have yellow and blue stripes and jet black eyes.
The bluefish, sadly, is the single remaining species of the Pomatomidae family. These marine pelagic fish thrive in temperate and subtropical waters. These are hunted for sport and food across the world. Bluefish have moderately proportionate bodies and an expansive, forked tail. Their pectoral fins and spiny first dorsal fin are folded back in the grove. With a dorsal grayish blue-green in color, their lower sides and the bellies are white. The average weight of a bluefish is 9kg which can reach up to 18 kg.
Thriving mostly in loose groups, these fish are very strong and aggressive. They are known for swimming fast and preying on the forage fish. They attack these fish in feed frenzies. They also feed on shrimp, squid, anchovies, grunts, weakfish, jacks and menhaden. They can even gobble their own juveniles and have cannibalistic eating habits.
Siamese Fighting Fish
Also called Betta fish, Siamese fighting fish is among the prettiest fish species of the world. Thanks to their vibrant and unique colors, people love these fishes in their aquariums. They belong to the Gourami fish family and are extremely territorial in nature. The males of this species are supremely aggressive. They can be seen fighting to the death if any other male Siamese fish enters their tank. In small aquariums, even the females tend to turn hostile towards the other fish of the same species. These fish are found in Thailand, Laos, Vietnam, and Cambodia. They inhabit floodplains, canals, and rice paddies. IUCN has listed the Siamese fighting fish as a vulnerable fish species because of the aquarium trades.
The European carp, colloquially called the common carp, live in freshwater beds like huge lakes and rivers across Europe and Asia. Common carp have adapted to varying environments and been domesticated across the world. Yet, the IUCN still considers their wild populations vulnerable. These are supremely invasive in nature and can even go on harming new habitats if they are not in proper control. They can easily survive for 45-47 years with no issues. They lay close to 300,000 eggs in one spawn.
Goldfish are freshwater fish and are among the most common species used in the aquarium trade. Native to East Asia, the selective breeding of goldfish started in Ancient China some thousand years back. Since then, various breeds have emerged, and they all vary in size, shape, fin, body, and colors. You can see them in black, orange, yellow, white, brown, and red.
Belonging to the Cichlid fish family, and are called by various common names such as tiger Oscar, velvet cichlid, and marble cichlid. These are native to the tropical regions of South America, and they are frequently sold as food in these areas. Other regions of China, Australia, and the United States, have also domesticated the Oscar fish. The United States, as well as Europe, often uses this fish in their aquariums. Living up to 10 to 15 years, Oscar fish possess a territorial behavior.
Also called Sheatfish, Wels catfish is a massive species of catfish. These are native to Central, Southern as well as Eastern Europe. Initially regarded as a prized sport fish, Wels catfish are now available all across the Eurasia region. These live in freshwater, and you can recognize them by their elongated whisker-like features, flat heads, and wide mouths. They can survive for as many as 60 years if they are safe from their predators and have abundant food.
Belonging to the Percidae fish family, sauger fish are freshwater fish. These are native to North America and account for the highest numbers of migratory percid of that region. They possess two dorsal fins; one is soft-rayed while the other is spiny. These predatory fish have adapted well to their habitat and can swim across fast currents without dragging their bodies much. They can weigh around 300-400 grams and are usually dark, brassy in color. They typically inhabit huge rivers which have pools.
The pools need to be 0.6m or even more in-depth. This freshwater fish mainly rely on other fish for their food and eat invertebrates and smaller fish for survival. Thanks to overexploitation, habitat loss, migratory barriers, and entrainment in the irrigation channels, sauger fish are steadily depleting in numbers.
The Northern Pike
The Northern pike belongs to the Esox genus of fish and is carnivorous in nature. They thrive on the brackish and fresh waters of our Northern Hemisphere and can grow up to a relatively big size. On average, their length can go up to 40 to 55 cm. The biggest pike of the world ever recorded was in 1986. It weighed a whopping 25 kilos! Northern pike fish come in olive green colors with yellow and white shading across their bellies. Their fins have some dark spots, while the flank possesses light spots. The fins can also be red in color at times. Thanks to a mutation in pike, some of these fish can also be silver in colors with bluish silver spots.
The Tench Fish
Usually known as the Doctor fish, tench fish live in brackish freshwaters and belong to the Cyprinid family. These fish are native to the Eurasian region and can be seen in the Yenisei River to the British islands. They live in slow-moving waters such as lakes and lowland rivers. Their olive green skin is in the shape of the common carp fish. They have square tail fins, and their fins are round in shape. The heaviest tench fish ever recorded was in 2001, and it weighed close to 7 kg. The male tench fish are usually smaller in size than the females, and even their fins slightly differ.
European eels are snake-like fish that belong to the catadromous family of fish. These can be 1.5m long and can survive for as many as 80 years in their captivity. One European eel was even recorded to have lived for a whopping 155 years! The European eel is now listed as a critically endangered species because of a decrease in 90% in merely 40 years. This has happened because of parasites, natural alterations in water flow, overfishing, and barriers to their migration such as reservoirs and dams.
The Guppy Fish
Popularly called the Million fish or the Rainbowfish, guppy fish are among the world’s most widely spread tropical fish. These are very popular in freshwater aquariums because of their attractive and vibrant colors on their tails and patterns and designs of spots across their bodies. Guppy is a very adaptable fish and can live in many varying ecological environments and conditions. The male guppies have smaller caudal fins and dorsal fins than the female ones.
Cisco fish belong to the Coregonus genus of fish. These are salmon fish but differ from the other salmon species of fish as their lower, and upper jaws are generally of the same lengths, but they have more gills than their counterparts. North America recently saw the evolution of this freshwater fish in the lake herring fish species. These can be as much as 40 cm in length and usually weigh close to 5 pounds.
On average, they can grow up to 28-38 cm in length. The slender bodies of these fish help them in swimming away from the predators. These silvery fish sport an incredibly beautiful pinkish iridescence on their side, making the Cisco fish so unique. These are freshwater fish surviving on zooplankton, insect larvae as well as fish larvae and eggs. They can even feed on minnow and other such smaller fish.
The black crappie is the common name given to Pomoxis nigromaculatus. These freshwater fish live in North America. These are darker than white crappie and have bluish-black spots on their bodies. Apart from that, the two species and only species of the crappie fish are pretty similar. Black crappies possess silvery-gray bodies covered with dark spots. This makes them different from all other fish in the water bodies. Their length can reach up to a maximum of 19.3 inches and can weigh up to 6 pounds.
Black crappies are found in the navigation pools of lakes, reservoirs, borrow pits and large rivers of North America and Canada. These usually eat small crustaceans and plankton, but the larger crappies can also feed on minnows, shad, and other such small fish.
Brown Bullhead Catfish
Brown bullhead is the common name given to Ameirus nebulosus. These catfish belong to the Ictaluridae family. Native to North America, brown bullhead catfish makes for a significant clan symbol for the Ojibwe group of Native America. These can be as long as 21 inches and come in shades of dark brown-green. They do not have any scales on their bodies, and their bellies are generally cream or white in color. These are omnivorous fish who are opportunistic bottom eaters. They feed on algae, crustaceans, mollusks, insects, crayfish, and many other tiny fish.
Their eyesight is very poor, and they depend on their pretty sensitive barbells for locating prey. The brown bullhead catfish usually live in slow-moving streams which are low in oxygen and have muddy conditions. You can also spot them in ponds and lakes.
Gold shiners are a type of cyprinid fish native to Quebec and eastern regions of North America. These make for a good baitfish and are mostly used for that purpose. This is because they have a lot of predators. These are the most popular fish cultured in the ponds of the region. Golden shiner is a tiny fish that usually grows to 7.5-12.5 cm in length. They have dark or olive green colors, and their bellies are silvery white. These are freshwater fish mostly feeding on algae, plants, zooplankton, and insects. Their eyesight is pretty sharp, which helps in locating their prey. These fish love the weedy regions and can survive in turbidity and low oxygen content. (See What is Blobfish (Psychrolutes marcidus)?)
The largemouth bass is the Micropterus salmoides, a gamefish native to the United States and Northern Mexico. These live in freshwaters and are carnivorous in nature. They have an olive-green body covered with dark black blotches. The largest largemouth bass fish ever recorded weighed 25 pounds and was 29.5 inches in length. They can live for as long as 10-16 years, depending on the abundance of food and the environment. These fish usually feed on small shrimp, scuds, insects, and small baitfish.
The full-sized adult bass fish can also eat up bats, small fish, crayfish, frogs, salamanders, and even snakes. They live in reservoirs, lakes, rivers, and other sources of freshwater bodies. These are invasive species as they can multiply rapidly.
Pimephales promelas, commonly called fathead minnow, are generally found in ponds, wetlands, and small lakes. You can also spot them in bigger lakes and streams. They are temperate freshwater fish and live all across central Canada to North America. They serve as good baitfish and can live in varying locations. Minnows are most popular for their production of Schreckstoff, a distress signal when they are under attack. Schreckstoff serves as an n alarm for other minnow fish around that region to flee away. Northern pike, walleye, largemouth bass, and a lot of other fish prey on the minnow.
Fathead minnows are omnivorous fish, and an adult minnow can be 2 to 3 inches long. They swim across dirt and silt to find crustaceans, insects, zooplankton, and other invertebrates underwater. Bottom detritus fathead minnow also feeds on phytoplankton and algae for survival.
Usually called the Yellow Pink, walleye fish lives in North America and Canada. These are pretty similar to blue walleye fish, which have now, presumably, faced extinction. Typically, they grow up to a length of 30 to 50 cm. This is, in fact, less than the potential size of a walleye. These carnivorous fish prey on minnows, leeches, crayfish, ciscoes, and yellow perch. At night, walleye fish swim into shoals and bars for catching their prey. The palatable taste of walleye is what makes them widely hunted. Due to their nocturnal eating habits, fishers can easily catch them at night. Minnows are usually used as baits for luring in the walleye.
Common dace is the popularized name of Leuciscus leuciscus. Primarily, it is a freshwater fish that can also live in brackish waters. These fish are from the Cyprinidae family and are found towards the north of the Alps in Europe and northern Asia. They mostly thrive in rivers and streams, and in many regions, these are used as baitfish. Common dace usually live in still, deep water and love clear streams. They can be as long as 40 cm and can weigh up to 1 kg. They can live for 16 years and are found in huge numbers.
Bigger predaceous fishes usually prey on these common dace fish. These are active and lively fish with a plethora of gregarious habits. Depending on their habitat, common dace can be pretty invasive. They lay pale yellowish eggs and eat worms, snails, larvae, insects, and occasionally, vegetable matter.
Found in North America, banded killifish are from the Fundulus genus. These temperate killifish live in freshwaters and weigh merely a few grams. On average, they can be 10 to 13 cm in length. Their dorsal fins are olive in color, and the ventral fins are white. Blackish and silver-white stripes run through the sides of the fish. The female species are bigger than the males, and their bands are darker on the sides. These fish move in schools and move in groups of three to six fish. Juvenile killifish travel in bigger groups. Their main diet comprises mosquitoes’ larvae, while they also eat insects, nymphs, turbellarians, and other tinier crustaceans.
Both the adult and juvenile banded killifish eat during the afternoons. In 2005, these fish were listed as a vulnerable species as there has been a steady depletion in their numbers over these years. They have to go through habitat degradation because of industrial development, watercraft activities, and a usually decrease in the aquatic vegetation.
The European Chub is the common name given to squalis cephalis. These freshwater species belong to the family of carp. Chubs are stocky in nature and have a huge round head. Their long and cylindrical bodies are covered in brownish-green scales. Their flanks have spots of pale golden shades. Their length can reach up to 30 to 60 centimeters. European chub lives in slow and moderate canals, rivers, and other stagnant waters.
They thrive on barbell regions of rivers where there are higher numbers of riffles and pools. The young chubs are more social than adult chubs which are generally solitary. This helps them in avoiding predators. These fish eat mollusks, worms, crustaceans, and insect larvae. The bigger chubs also feed on frogs, dace, minnows, tiny birds, common roach, as well as berries. Metal and microplastic pollution can contaminate the chub population.
Particles like magnesium, sodium, copper, and plastic are present in regions where the chub habitat gets exposed to industrial waste and garbage. The young and juvenile chub fish are specifically prone to this metal contamination. This can have a huge impact on the mortality rates of these fish.