COMMON INDIAN FISHES

The subcontinent of India has a large number of rivers besides lakes, backwaters, lagoons and swamps. The two largest rivers, the Ganges and the Indus, originating from the Himalayan mountain ranges flow down through the entire length and breadth of Northern India and finally enter their respective estuaries to reach the sea. Peninsular India also has large rivers like the Godavari, the Krishna and the Kaveri besides innumerable smaller ones. The total length of rivers in India is estimated at about 27,360 km. All these rivers, their tributaries, canals and irrigation channels have roughly an area of 1,12,650 sq. km. and afford a wide variety of habitats to fishes.

India is bordered on the east by the Bay of Bengal and on the west by the Arabian Sea, the two merging on the southernmost tip of the peninsula with the Indian Ocean. India, thus, has a coastline of about 4,700 km. The continental shelf bordering the Indian coast has a total area of about 2,59,000 sq km. This vast area is the home of infinite varieties of marine fishes. Beyond the continental shelf lie the oceanic waters, home of some of the large sharks and rays, as well as bony fishes like the tunas, sail fishes and sword fishes. Thus, the total area of freshwater and marine resources of India exceeds several million square kilometers but at present not more than one million sq km are being exploited.The fishes are classified broadly into ...

• Elasmobranchs

• Teleosts.

ELASMOBRANCH FISHES

As already explained, sharks and rays constitute the cartilaginous group, whose members are mainly denizens of the seas and oceans, except a few interesting estuarine and migratory species.

Super order Pleurotrotremata Or Sharks

On account of their large size and predacious habits, sharks are more prominent and better known. The present-day sharks are classified under three major groups or orders, viz., (i) Notidanid or Hexanchid sharks; (ii) Galeoid or Lamna-like sharks; and (iii) Squaloid sharks. All are represented in the Indian seas.

Notidanid or Hexanchid sharks are rare and are considered the most primitive. Gill-slits may be 6 or 7 pairs. The dorsal fin single. The only member found in India is Heptranchias platycephalus. This shark has an elongate body, with a round or obtuse snout. Eyes without nictitating membrane. Spiracles small. Seven pairs of gill-clefts.

Galeoid sharks (Lamniformes) are the largest group and include all the well known sharks of the world. Gill-clefts 5; 2 dorsal fins; one anal fin; no spine. The members of this suborder fall under six distinct families, viz., Odontaspidae, Lamnidae, Orectolobidae, Scyliorhinidae, Carcharhinidae, Sphyrinidae.

Family : Odontaspidae (Sand Sharks)

Carcharias tricuspidatus, known as Wagir in Bombay, is the only member of this family recorded in India. Found off Bombay and Sind coasts. Average size 3.5 m but may attain 6-metre length. Ferocious and dangerous to man and other fishes.

Family: Lamnidae (Mackerel Sharks)

Popularly known as mackerel sharks, on account of the perfection and similarity of body-shape to the teleost fish, mackerel. Latona is a well-known member. Carchardon is another example and is popularly called man-eater as it is known to attack human beings. Both these sharks do not occur in the Indian seas, however, Isurus (commonly called Porbeagles) and Alopias (Thresher sharks) are the only Lamnid sharks recorded in India.

Family Orectolobidae is a large and varied one. Oreclolobus, the carpet-shark, is a noted member. In India the following genera are recorded. Chiloscyllium, Nebrius, Stegostoma, and Rhincodon, the last being the, most well-known.

Rhincodon typus Smith or whale shark is known as Karanj or Bahiri in Bombay. As the common name indicates, this shark resembles whales in size. In fact, Rhincodon is the largest fish known in the world today, measuring about 15.2 metres. The Indian species, however, ranges from 4 to 9 metres. They are surface swimmers and feed on plankton. They are very rich in liver oil and are economically very important. Related to this is a small whale shark, 2-9 metres long, Nebrius ferrugineum, common in Bombay where it is known as Sunera. It is also rich in liver oil. Another Indian member is Stegostoma varium commonly called Tiger shark, because of its vivid stripes and markings like those of a tiger. It grows to 5.5 m in length and is valued for its flesh and oil. Common at Madras and Trivandrum.

Family Scyliorhinidae is a large family of I 1 or 12 genera. The most important commercially is Carcharhinus or Blue sharks. They are elegant, blue-coloured sharks. About 12 species are found in the Indian seas. They are more abundant on the Malabar coast.

Carcharhinus gangeticus is found in the Bay of Bengal and in all the large rivers. Those living in the Ganges ascend upstream and are among the few sharks adapted to freshwater. All species of Carcharhinus are valuable sources of liver oil and are caught in plenty for the extraction of oil. Another important example is Scoliodon, popularly known as dog-sharks or dog-fishes. Theyare comparatively small, ranging from 0.6 to 0.8 m long.  There are two or three species which are esteemed as food as well as sources of oil. On account of its small size, 27 coliodon is the most popular shark for type-study in biology in colleges throughout India. Reference may also be made to caleocerdo, another member of this family, found along both the Malabar and the Coromandel Coasts. They are medium-size fishes 3.6 to 4.2 m long and yield large quantities of oil.

Family: Sphyrinidae (Hammer-headed sharks)

Hammer-headed sharks are notable exhibits in large marine aquaria on account of their bizarre appearance. The head of this shark is flattened in front and expanded sideways, thus resembling a hammer. The eye is located at the tip of each lateral extension of the head. These sharks are ferocious and lash at their prey with their heads. They are caught for their oil, although the yield is comparatively low. Four species have been recorded in the Indian seas, the most important being Sphyrna blochii (synonymous with Zygaena blochii, Day) found in the Bay of Bengal and off the Bombay coast.

The third major group of sharks are the Squaloids composed of three families. Family Squalidae consists of small-sized sharks resembling the dog-fishes. One of the distinguishing features is the absence of the anal fin. Either of the dorsal fins is preceded by a spine and the group is, therefore, commonly referred to as spiny dog-fishes. There is a tendency for the snout to become spatulate and the spiracles larger. The two well-known members are Centrophorus and Centroscyllium; both are abundant in the Bay of Bengal and the Arabian Sea.The other two families, Squatinidae and Pristiophoriclae, are not found in India.

Superorder Hypotremata Or Batoidei (Rays)

Rays which constitute the second major group of Elasmo-branchs are distinguished from sharks by a dorso-ventrally flattened body with five gill-openings, which are situated on the under surface of the body. Indian seas are rich in them. Typical rays are classified under the order Batea [Rajiformes), while those with electric organs are referred to under Narcohatea (Torpedeniformes). The well-known members of Batea are described below.

Family: Pristidae (Saw fishes)

These fishes are characterised by the possession of an elongated, toothed, saw-like rostrum, with which it attacks other fishes. There are two species in India, Pristis cuspidatus and Pristis microdon; both are invaluable for liver oil of high vitamin value. Pristis should not be confused with the saw-shark Pristiophorus, which has a toothed rostrum. The shark can be distinguished by its lateral gill-openings. Both are dangerous to man.

Family: Pdtinobatidae (Guitai Fishes)

These are rays with a depressed body, a tapering snout and an elongated caudal region, thus resembling the musical instrument, the guitar. There are three genera in India. Rhynchobatux, the larger of the two, is about 2.5 m long, with liver weighing about 4 kilograms and is caught for the extraction of liver oil. Its flesh is also useful as food, either in the fresh or dried state. The other genera are Rhina and Rhinobatos which are smaller types and used mainly as food.

Family: Dasyatidae

These are the famous rays which can inflict wounds on their victims by means of the sting on the tail. The sting is a modified spine, provided with poison glands and may be 1 or 2 in number. There are several genera and species in the Indian seas of which Dasyatis is the best known.

The other genera of sting-rays are Gymnur, Urogymnus and Taeniura. Sting-rays though smaller in size are valuable in commercial fisheries. Their flesh is edible and liver yields a fair amount of oil.

Family: Rhinopteride (Cow Rays)

These are rays in which the head is divided into two rounded lobes by a deep notch and resembles Somewhat a cow's head. The disc-like body is quadrangular. The tail is long and whip-like. These fishes are about a metre long. They are considered economically not profitable as the oil content is low. There are four species of Rhinoptera in India.

Family: Myliobatidae (Eagle Rays)

In these fishes, the pectoral fins resemble the outspread wings of an eagle and hence the popular name. Tail is whip-like and bears a spine. Two species are commonly found in India. Aetomylaeus nichofii (Syn. Myliobatis niehofii, Day) occurs in the mouth of the Ganges and Chilka Lake and also along the east and west coasts. . Etobatis narinari is the spotted Eagle Ray and is the only species found in the Indian seas.

There are several well-known species of the Narcobatea or Torpediniformes in India, of which a few may be mentioned here.

Torpedo marmorata is the common or Marbled Electric Ray measuring about 30-50 cm across the body, The electric organs are two large bodies in the gill region.

Arcine brunnea (Annandale) is the popular Electric Ray of the coastal waters from Bombay to Hooghly.

Narke dipterygia Schn. is found on the Coromandel coast and also in estuaries of West Bengal and Orissa.

TELEOST FISHES

  The common bony fishes of India will be dealt with under two headings.

• Fresh-water

• Marine

Fresh-water

  The carps and catfishes of the order Cypriniformes or Os tario-physi constitute about 64% of the fresh-water fishes of India and are very important food fishes. The carps and their allies form the division Cyprini, consisting of about 200 genera.

Family: Rhinopteride (Cow Rays)

These are rays in which the head is divided into two rounded lobes by a deep notch and resembles somewhat a cow's head. The disc-like body is quadrangular. The tail is long and whip-like. These fishes are about a metre long. They are considered economically not profitable as the oil content is low. There are four species of Rhinoptera in India.

Family : Myliobatidae (Eagle rays)

In these fishes, the pectoral fins resemble the outspread wings of an eagle and hence the popular name. Tail is whip-like and bears a spine. Two species are commonly found in India. Aetomylaeus nichofii (Syn. Myliobatis niehofii, Day) occurs in the mouth of the Ganges and Chilka Lake and also along the east and west coasts. Aetobatis narinari is the spotted Eagle Ray and is the only species found in the Indian seas.

There are several well-known species of the Narcobatea or Torpediniformes in India, of which a few may be mentioned here.

Torpedo marmorata is the common or Marbled Electric Ray measuring about 30-50 cm across the body, The electric organs are two large bodies in the gill region. Arcine brunnea (Annandale) is the popular Electric Ray of the coastal waters from Bombay to Hooghly.

Narke dipterygia Schn. is found on the Coromandel coast and also in estuaries of West Bengal and Orissa.