Biology of cultivated Indigenous and exotic fish species

Common carp

• Two varieties are under culture in Nepal i.e. Scale carp or German carp ( Cyprinus carpio var. communis) and Mirror carp or Israeli carp (Cyprinus carpio var. specular) with the body covered unevenly with few large shiny scales.
• Is characterized by a flat and deep body, short and small head, protractile mouth, and pairs of maxillary barbells.
• The dorsal fin is long with a sharp spine.
• The bottom feeder is omnivorous and feeds on insect larvae, worms, and mollusks and accepts formulated feed also.
• Multiple breeders can breed up to 5 times a year.
• Sexual maturity is attained in the first or second year.
• Breeds easily in ponds without hypophysation.

Grass carp ( Ctenopharyngodon Idella)

• An exotic carp was brought to Nepal from India and Japan in 1967 and 1968 respectively.
• The body is elongated and cylindrical with large, greenish scales.
• Head broad, barbells absent and mouth sub-terminal with upper jaw slightly longer than the lower jaw.
• Usually, it has a toothless mouth but has specialized pharyngeal teeth for grasping aquatic vegetation.
• Gill rakers are short and sparse.
• Colum/marginal feeder and herbivorous.
• Digestion is incomplete and about half the food material ingested is excreted as feces.
• One of the fast-growing fish attains 1-2 kg in the first year.
• The largest size is 1.5m and 50 kg.
• Seasonal breeder, matured in 2-3 years and induced breeding is done by hypophysation.
• Breeding season is April/May when the water temperature is 22-27⁰

Silver carp ( Hypophthalmichthys molitrix)

• Exotic fish were introduced in Nepal from India and Japan in 167 and 1968, respectively.
• Fish is characterized by a flat and laterally compressed body covered by small silvery scales.
• Head small, barbells absent, mouth upturned with lower jaw longer than upper and the abdominal keel is complete.
• Gill rakers are long and dense, connected and covered with a spongy sieve membrane.
• Surface, phytoplankton feeder with young fry feed on zooplankton.
• Growth in the first year is 1-2 kg, largest size attains 40-50 kg.
• Seasonal breeder, matured in 2-3 years and induced breeding is done by hypophysation.

Bighead Carp ( Aristichthys nobilis)

• Exotic fish were introduced to Nepal from America and Hungary in 1969 and 1972, respectively.
• The body is flat, laterally compressed, and covered by small slivery scales brownish above.
• Headlong and massive, barbels absent, mouth large, upturned with lower jaw longer than upper, and the abdominal keel is incomplete.
• The posterior margin of the pectoral fin extends beyond the base of the pelvic fin.
• Surface zooplankton feeder.
• Growth in the first year is 1-2 kg, largest size attains 40-50 kg.
• Seasonal breeder, matured in 2-3 years and induced breeding is done by hypophysation.
• Docile and hardy fish for transportation and handling.

Rohu ( Labeo rohita)

• Tasty among the cultivated carp in Nepal.
• Characterized by an elongated and cylindrical body, small or pointed head, sub-terminal mouth, and one pair of maxillary barbels.
• The lips are thick and fringed.
• The body color is dull reddish on the sides and whitish on the belly.
• Column feeder feeds on plant matter including decaying vegetation.
• Growth is slow in the first year ( 900 g), the largest size attained is 1 m and 30 Kg.
• Seasonal breeding and induced breeding is done by hypophysation.
• Breeding season is from June to August.

Catla/ Bhakur ( Catla catla)

• Fast-growing fish among the indigenous cultivated carp.
• Deep, laterally compressed body with a massive head and large upturned mouth.
• Barbels are absent and lips are non-fringed.
• The body color is grayish to silvery on the upper sides and whitish on the belly.
• Surface, zooplankton feeder but young ones feed both zooplankton and phytoplankton.
• Growth in the first year is 1-1.5 kg.

Mrigal/ Naini ( Cirrhinus mrigala)

• Characterized by an elongated and cylindrical body, small head, and sub-terminal mouth with thin non-fringed lips.
• One pair of small barbels are present.
• The upper jaw is longer than the lower jaw.
• The body color is grayish on the dorsal side and whitish on the belly but is not pinkish as rohu.
• Bottom feeders, are omnivorous and feed on detritus, mud organisms, decaying plant and animal matter, however, young ones feed on zooplankton.
• The largest size attains is 90 cm and 30 kg.

Nile tilapia ( Oreochromis niloticus)

• Native to Northern and Central African rivers.
• Was first introduced to Nepal from Thailand in 1985.
• Characterized by the presence of long spiny dorsal fin, interrupted lateral line, and the presence of distinct black stripes on the body and tail.
• The body color of the adult male is the reddish underside and red coloration at the tip of the causal fin while the adult female is the yellowish underside and brownish with stripes on the dorsal surface.
• Can grow up to 500 g in one year and is a prolific breeder.
• Can attain sexual maturity and spawns at ages of 4-6 months and size of less than 50 g.
• Breeding mayn’t occur every month, but under favorable environmental conditions, a female will normally produce several batches of young in a year.

Silver barb ( Puntius gonionotus)

• Introduced to Nepal in 1991 from Bangladesh.
• The body is flat, laterally compressed, and covered by large silvery scales, sometimes with a golden tint.
• The head is small, the snout pointed, the mouth terminal, barbells are very minute.
• Very few tubercules are present on the snout which isn’t visible without magnification.
• Herbivorous but feeds on both plant and animal matter including phytoplankton, zooplankton, filamentous algae, higher plant materials, and detritus.
• Adult fish feed on macrophytes.
• Growth in the first year is about 500g, largest size attained at 40 cm and 1.5kg in pond condition.
• Sexual maturity is attained towards the end of the first year and induced breeding is done by hypophysation.

African catfish ( Clarias gariepinus)

• Called ‘Mangur’ in Nepal.
• Has a long and cylindrical body, a flat bony head, and a broad terminal mouth with four pairs of barbels.
• Fish is usually of dark grey or black coloration on the dorsal side, fading to a white belly.
• The dorsal and anal fins are very long and without spines, but the pectoral fins have spines. The caudal fin is rounded.
• Is carnivorous but shows an omnivore feeding habits.
• Hasair-breathing labyrinthine organ ( called rosette or air-tree) arising from gill arches.Hence, able to survive on shallow, muddy water for a long time.
• Able to crawl on the wet ground.
• Growth in the first year is 1.5-2 kg, largest size attains 20-30 kg.
• Seasonal breeder, matured in 1-2 years and induced breeding is dine by hypophysation.

Sahar or Mahseer ( Tor putitora)

• Important edible fish in the rivers and tributaries of Nepal.
• Resembles a typical carp in structure and appearance.
• The body is semi-round and slightly flattened along the ventral surface from near the mouth opening to the anus, and there is sudden tapering of the body just after the anal region.
• Eyes are large, round, and situated more towards the dorsal surface.
• The head is provided with two pairs of barbels.
• The entire body, except the head and fin, is covered with large-sized scales.
• Attains m length and sometimes exceeding 30 kg.
• During spawning season, males develop strong tubercules and are easily distinguished from females.
• Are long-lived and slow-growing fish.
• Feeds mainly on drifting aquatic and terrestrial insects.
• Attains sexual maturity in 2-3 years and breeds in Feb/Mar. Or Oct./Nov.

Rainbow trout ( Oncorhynchus mykiss)

• Native to USA and was introduced to Nepal in 1998 from Japan.
• The body is elongated and laterally compressed with a rounded snout.
• The Upper side of the head is blue-green, yellow-green, or almost brown.
• The sides are silvery and marked with a bright pink-bluish to red band and many small black spots.
• The underside is silvery, white, or grey to yellowish; the dorsal and caudal fins have radiating rows of black spots.
• Highly carnivorous and a predator with a varied diet.
• Feeds on animal matter like insects, mollusks, fish eggs small fishes, etc.
• Needs a high protein content feed for culture.
• Growth is 200-300 g in the first year.
• Seasonal breeder, matured in 3-4 years and induced breeding is done without hypophysation.

Pangas catfish ( Pangasius hypophthalmus)

• Native to rivers of South Asia.
• The body is long and latterly flattened with no scales.
• The head is relatively small.
• The mouth is broad with small sharp teeth on the jaw, vomerine, and palatal bones.
• Eyes are relatively large.
• Two pairs of barbels are present, the upper shorter than the lower.
• Fins are dark grey or black.
• Gill rakers are normally developed.
• Juveniles have a black stripe along the lateral line and another long black stripe below the lateral line.
• However, large adults are uniformly grey and lack the stripping.
• The sides are silvery in color.
• Omnivorous and the diet mainly consists of crustaceans, other fish, and plant matter.
• Seasonal breeder, matured in 2-3 years and induced breeding is done by hypophysation.
• Cultured in high stocking density.

Freshwater prawn ( Macrobrachium rosenbergii)

• Are crustaceans, not real fish?
• Live in freshwater, but their larval stages require brackish water to survive.
• The body is usually greenish to brownish grey, sometimes more bluish and darker in larger specimens.
• Have a hard exoskeleton over a segmented body.
• Have five pairs of legs on the main part of the body, plus five pairs of swimmerets on the abdomen or tail.
• Have stalked eyes and two pairs of antennae.
• Males can reach a body size of 32 cm; females grow to 25 cm.
• Larvae go through 11 distinct stages before metamorphosis, each with several distinguishing features.
• Are omnivorous and bottomfeeders.
• May mature and breed year-round except in colder months.
• Reared artificially in the hatchery by collecting the nauplii that hatch out from eggs released bbybyey berried females
• The larval stage requires brackish water ( 10-15 ppt) to survive.