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UNIT - ONE

Introduction of aquaculture and fisheries

Learning outcomes

After completion of this lesson students should know about,

 General introduction to fish, fisheries and its types.

 General characteristics of indigenous and improved fish species with their

habit and habitat.

 General principle of aquaculture, farm design and pond construction.

Fish

Fishes are the first successful class of the chordates. They are aquatic cold blooded

vertebrates which breathe by means of pharyngeal gills, propelling and balancing

themselves by means of fins. About 40,000 living spp. of fish are found in the world.

Fisheries

Aquatic organisms, which are exploitable by the public as a common property

resource with or without appropriate license is known as fishery. For example:

Riverine fisheries, lake fisheries, fishing on rice fields, wetlands etc. Fisheries can

be divided into 3 types

a) Capture fisheries

b) Enhance fisheries

c) Culture fisheries or aquaculture

A. Capture fisheries:

The capture fisheries are characterized by the following:

 No stocking

 No management practices (eg. fertilization, liming, monitoring etc.)

 Only harvesting.

 Artificial feeding should not provide.

B. Enhance fisheries

The characteristics of enhance fisheries are as follows:

 Only stocking.

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 No management practices (eg. Monitoring & supervision, fertilization, Record

keeping, liming etc.)

 Harvesting.

C. Culture fisheries or aquaculture

Aquaculture is derived from two words ‘Aqua’ means water and ‘culture’ means

farming. Thus, aquaculture is the farming of aquatic organisms: fish, mollusks,

crustaceans, aquatic plants, crocodiles, alligators, turtles, and amphibians. Farming

implies some form of intervention in the rearing process to enhance production, such

as regular stocking, feeding, protection from predators, etc.

1.1 Basic principles of fish culture

Fish Culture is being one of the most productive cultural practices. Therefore, fish

culture is very common and widely practiced in most countries of the world. This

fish culture practice do not only produces nutritious food improving nutritional status

but also helps in generating income and provide job opportunities to the number of

the people. The fish culture is comparatively easier, thus a person affords to look

after larger production areas in compare to other agricultural activities. Moreover,

by this practice system, fish is produced at low level in lower cost and the increased

in production give economic benefit to the grower. The construction of a water body

in the form of small or big pond size do not only facilitates to carry fish culture but

it also helps in conserving water to use as per the need arises e.g. to fight against the

fire or to save the major agricultural crop by irrigation in drought condition.

Sustainable fish culture requires following points that should be followed;

 Production technology should follow scientific manner.

 It should be fully developed and feasible.

 It should be socially acceptable and economically viable.

 Water quality should be managed properly and regularly.

 It should not provide hazardous effect to the environment.

 Feeding should be based on water temperature, body weight and growth stage

which will minimize the losses and maximize the profit.

 There should be appropriate stocking density & harvesting techniques.

 There should be good disease management practices.

Aquaculture and Fisheries : Grade 10 3

 Production technology includes the fish husbandry, seed storage, growth,

harvesting facility and culturing of species.

 All the production technology should be ecofriendly & maintain species

diversity.

 Always stock healthy, disease free, true to type seed.

1.2 Habit & habitat of improved fish varieties

Habit may be define as a usual way of behaving something which dose in regular

and repeated way.

A habitat is an ecological or environmental area that is inhabited by a particular

species of animal, plant or other type of organism. The term typically refers to the

zone in which the organism lives and where it can find food, shelter, protection and

mates for reproduction, utilizing the qualities the species has adapted to survive

within the ecology of the habitat. It is the natural environment in which an organism

lives, or the physical environment that surrounds a species population.

Habit and habitat of fish species helps to know about the nature of fish varieties. It

also helps to know about their origin, growth habit, food, shelter, environmental

requirement as well as their reproduction behavior. it also helps to differentiate the

warm and cold fishes within a improved species.

Habit and habitat of major carps (Indian and Chinese carps)

Carp are a large freshwater fish native to central Asia. Introductions in many

countries have helped to make carp the most widely distributed fresh water fish in

the world. They are extensively farmed in Europe, Asia and the Middle East, and are

a popular angling fish in Europe. Carp are very versatile, and can live in a great

variety of habitats including highly degraded areas. Carp are usually found in still

or slowly flowing waters at low altitudes, especially in areas where there is abundant

aquatic vegetation. They are also found in brackish lower reaches of some rivers and

coastal lakes.

They are capable of tolerating a wide range of environmental conditions. They have

a greater tolerance of low oxygen levels, pollutants and turbidity than most native

fish, and are often associated with degraded habitats, including stagnant waters.

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Changes to water flows, declining water quality and other changes to river habitats

over the past few decades have negatively affected many native fish while favoring

carp. Carp are omnivorous, and their diet varies depending on what is available. They

consume a range of small food items such as mollusks, crustaceans, insect larvae and

seeds. These food items are sucked up (along with mud and water) from the bottom

and filtered out using the gill rakers.

Under suitable conditions, carp are highly prolific. They mature early as early as 1

year for males and 2 years for females and the females produce large numbers of

sticky eggs (up to 1.5 million for a 6kg fish).

Habit and habitat of indigenous fish

Rohu

Rohu is a fish of the carp family found commonly in rivers and freshwater, lakes and

around Southeast Asia, Pakistan, Nepal, Myanmar and Bangladesh in addition to

Thailand. Rohu is the natural inhabitant of freshwater sections of the rivers. Rohu

thrives well in all fresh waters below an altitude of approximately 600 m. Rohu is a

bottom feeder and prefers to feed on plant matter including decaying vegetation.

Rohu attains maturity towards the end of the second year in ponds. The spawning

season of rohu generally coincides with the southwest monsoon. Spawning takes

place in flooded rivers. The fecundity of rohu varies from 226,000 to 2,794,000,

depending upon the length and weight of the fish and weight of the ovary. Spawn

may be collected from rivers and reared in tanks and lakes.

Naini / Mrigal

Mrigal inhabits all the major river systems of India, Nepal, Pakistan, Bangladesh and

Burma. The adult fish feeds upon filamentous green algae, diatoms, pieces of higher

plants, decayed vegetable, mud and detritus. It is basically a bottom feeder and hence

suitable for cultivation with column and surface feeder carps in ponds. Mrigal

usually attains maturity within 1 or 2 years depending upon the agro climatic

conditions of the location. Fecundity ranges between 1, 24,000 to over 1,900,000

depending upon size. Spawning season is linked with the onset and duration of the

southwest monsoon. It does not breed in ponds, but can be easily bred in bunds and

by hypophysation. It is now being induced to breed twice within the same spawning

Aquaculture and Fisheries : Grade 10 5

season. Rearing of seed is usually undertaken in seasonal or perennial undrainable

ponds. Under pond culture conditions it grows to over 1 kg in one year.

Catla/ Bhakur

Catla is the fastest growing Indian major carp species and widely distributed

throughout India, Nepal, Pakistan, Burma and Bangladesh. It inhabits the surface

layer of water and feeds upon plankton. Adult stages are predominantly zooplankton

feeder, occasionally taking in decaying macro vegetation, phytoplankton and smaller

mollusks. It attains maturity in the second year of life and carries over 70,000 eggs

per kg body weight. It naturally breeds in rivers during monsoon season and under

control conditions in bunds as well. It does not breed in ponds. However, it responds

well to hypophysation techniques. Seeds are easily reared in undrainable ponds of

relatively smaller size. Under composite fish culture in ponds it usually grows to

over 1 kg in one year.

1.3 Indigenous & exotic fish species, their identification & body structure

Indigenous fish species

A native fish species that is indigenous to a specific place or regions which are

favorable and suitable to that environment and exist from a long period of time is

known as indigenous fish species.

Table 1: Indigenous fish species of Nepal & their present status

S.N Scientific name Local Name Status

1 Labeo rohita Rohu Well establish, warm water fish

2. Cirrhinus mrigla Naini Well establish, warm water fish

3. Catla catla Bhakur Well establish, warm water fish

4. Tor tor Sahar Confined to research station, cool

water

5. Nelissocheilus

hexagonolepis

Katle Confined to research station, cool

water

6. Labeo dyocheilus Gardi Not in culture

7. Tor putitora Mahaseer Culture in limited scale, cool water

Rohu: - Labeo rohita

Rohu is considered as tastier fish species among the cultivated carps in Nepal. It is

characterized by an elongated and cylindrical body; the body color is dull reddish on

the sides and whitish on belly. The big fish attains to 2' - 3' in length. Head is small

than its body size and other characteristic are as follows:

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 Sub-terminal mouth parts and 1 pairs of maxillary barbells, the lips are thick

and fringed

 Column feeder, herbivorous in feeding nature. The fish feed on small plants

and decomposed materials of the pond and grows to a large size.

 It attains size of 900 gm at first year and up to 30 kg at maturity.

 Sexual maturity is attained towards the end of the second year.

 Rohu is seasonal breeder and artificial breeding is done by hypophysation. The

breeding season is June to August when the temperature is 25-30 ̊c

Fig.1: Rohu (Labeo rohita)

Catla/Bhakur: Catla catla

Catla is a fast growing fish among the indigenous cultivated carps. The barbells are

absent and lips are non fringed. Body color is grayish to silvery on upper sides and

whitish on belly and other characteristic of Catla/Bhakur are as follows:

 Fast growing fish, deep laterally compressed body with massive head.

 Large upturn mouth.

 It is surface Zooplankton feeder but young ones feed both zooplankton and

phytoplankton.

 It attains 1-1.5 kg at first year over 1.5 m length and size up to 45 kg.

 Catle is seasonal breeder and artificial breeding is done by hypophysation. The

breeding season is June to August when the temperature is 25-30 ̊c.

Source : www.google.com.np/search?q=rohu

Aquaculture and Fisheries : Grade 10 7

Source : www.google.com.np/search?q=Catla

Fig.2: Catla/Bhakur(Catla catla)

Mrigal / Naini: - Cirrhinus mrigal

Among indigenous fish species mrigal is next in importance to Rohu and catla for

culture. This fish is characterized by elongated and cylindrical body and other

importance characteristics of the Mrigal / Naini are as follows:

 Small head and sub-terminal mouth one pairs of small barbells are present.

 Thin non fringed lips ,upper jaw is longer than lower jaw

 Marginal and bottom feeder, omnivorous in nature and feeds on detritus mud

organisms, decaying plant and animal matter however young ones feed on

zooplankton.

 Largest size attains up to 90 cm and 30 kg .time maturity and breeding behavior

is similar to rohu and catla.

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