List of largest fish

Lobe-finned fish (Sarcopterygii)

The largest living lobe-finned fish is the coelacanth. The average weight of the living West Indian Ocean coelacanth, (Latimeria chalumnae), is 80 kg (180 lb), and they can reach up to 2 m (6.6 ft) in length. Specimens can measure up to 110 kg (240 lb). The largest lobe-finned fish of all time was Hyneria at up to 5 m (16 ft).

The coelacanth is one of the strangest and most primitive fish

Latimeria chalumnae replica

Hyneria

Lungfish (Dipnoi)

The largest lungfish, the African lungfish (Protopterus aethiopicus), is smooth, elongated, and cylindrical with deeply embedded scales. The tail is very long and tapers at the end. They can reach a length of up to 2 m (6.6 ft) and may weigh as much as 50 kg (110 lb). The pectoral and pelvic fins are also very long and thin, almost spaghetti-like. The newly hatched young have branched external gills much like those of newts. After 2 to 3 months the young transform (called metamorphosis) into the adult form, losing the external gills for gill openings. These fish have a yellowish gray or pinkish toned ground color with dark slate-gray splotches, creating a marbling or leopard effect over the body and fins. The color pattern is darker along the top and lighter below.

Spotted African lungfish, Protopterus dolloi

Ray-finned bony fish (Actinopterygii)

The largest living bony fish (superclass Osteichthyes, which includes both ray-finned and lobe-finned fish) is the widely distributed ocean sunfish (Mola mola), a member of the order Tetraodontiformes. The record size sunfish crashed into a boat off Bird Island, Australia in 1910 and measured 4.3 m (14 ft) from fin-to-fin, 3.1 m (10 ft) in length and weighed about 2,300 kg (5,100 lb).

A sunfish caught in 1910, with an estimated weight of 1600 kg (3500 lb)

The extremely rare king of herrings or oarfish, the longest of all bony fish. As to length, the longest extant bony fish on earth is the king of herrings or oarfish (Regalecus glesne). Slender and compressed, this fish averages over 6 m (20 ft) long at maturity. A specimen caught in 1885 of 7.6 m (25 ft) in length weighed 275 kg (606 lb). The longest known king of herrings, which was hit by a steamship, was measured as 13.7 m (45 ft) long, but unverified specimens have been reported up to 16.7 m (55 ft).

The extremely rare king of herrings or oarfish, the longest of all bony fish.

Much larger bony fish existed prehistorically, the largest ever known having been Leedsichthys, of the Jurassic period in what is now England. This species is certainly the largest bony fish ever and perhaps the largest non-cetacean marine animal to have ever existed. Estimates of the size of this fish range from 21 to 27 m (69 to 89 ft) and mass from 20 to 50 tons. A maximum size of 22 m (72 ft) and 25–30 tons has been deemed to be most realistic.

A 12-metre-long (39-foot-long) Leedsichthys compared to a human being

The remains of a 1000 kg beluga sturgeon, one of the largest bony fish

The Pacific halibut, largest of the flatfish, displays its effective camouflage. 

A large alligator gar, the largest freshwater fish in North America

The largest bristlemouth, the short-tailed barbeled dragonfish

Cartilaginous fish (Chondrichthyes)

The cartilaginous fish are not directly related to the "bony fish," but are sometimes lumped together for simplicity in description. The largest living cartilaginous fish, of the order Orectolobiformes, is the whale shark (Rhincodon typus), of the world's tropical oceans. It is also the largest living animal that is not a cetacean and, like the largest whales, it is a docile creature that filter-feeds on tiny plankton. An average adult species measure 9.7 m (32 ft) long and weigh an average of 9 tonnes. The largest verified specimen was caught in 1949 off Karachi, Pakistan and was 12.7 m (42 ft) long and weighed 21.5 tonnes. Although many are dubious, there are several reports of larger whale sharks, with reliable sources citing unverified specimens of up to 37 tonnes and 17 m (56 ft).

A large tiger shark ranks as the biggest of ground sharks.

Tiger shark measuring 18 FOOT caught off Seven Mile Beach, Australia

The giant guitarfish is largest species in the skate order.

The dramatically large mouth of the basking shark, the second largest living fish.

Spiny sharks (Acanthodii)

The largest spiny shark was Ischnacanthus. Some species were of large size, up to 2 m in length.

Ischnacanthus

Armored fishes (Placodermi)

The largest known fishes of the now-extinct class Placodermi were Dunkleosteus and Titanichthys. These particular animals may have reached lengths of 10 m (33 ft) and are estimated to have weighed in at 3.6 tons.

Dunkleosteus

Titanichthys termieri from Late Devonian of Morocco

Hagfish (Myxini)

The hagfish, which are not taxonomically true fish, are among the most primitive extant vertebrates. There is only one order and family in this animal class. All of the 77 known species have elongated, eel-like bodies but can immediately be distinguished by their strange downward-facing mouth, among other unique morphological features. The largest form is the Goliath hagfish (Eptatretus goliath). This species can range up to 1.28 m (4.2 ft) in length and weigh to 6.2 kg (14 lb).

Pacific hagfish trying to hide under a rock

Lampreys (Petromyzontida) Lampreys (Petromyzontida)

As with the similarly unique hagfish, lampreys appear eel-like in shape but are unique enough to earn their own class. These creatures have cartlaginous skeletons and have been evolving separately from any other group for over 400 million years. They are predatory and often attach themselves to a fish or other small animal and gradually drain blood and organs. The largest species is the sea lamprey (Petromyzon marinus), which can grow to 1.2 m (3.9 ft) and weigh 2.5 kg (5.5 lb).

Sea lamprey

Source: Wikipedia; Picture collected from Internet