Aquaculture in India has evolved as a viable farming practice over last three decades with considerable diversification in terms of species and systems, and has been showing an impressive annual growth rate of 6-7%. While the carp-based freshwater aquaculture, mainly constituted by the Indian major carps, viz., catla, rohu and mrigal, has been contributing over 90% of the aquaculture production satisfying the domestic need, the shrimp-based coastal aquaculture with only about 5% share contributes much of the export earnings.It Includes Marine and Inland
Pelagic fish live in the pelagic zone of ocean or lake waters - being neither close to the bottom nor near the shore - in contrast with demersal fish, which do live on or near the bottom, and reef fish, which are associated with coral reefs The marine pelagic environment is the largest aquatic habitat on Earth, occupying 1,370 million cubic kilometres (330 million cubic miles), and is the habitat for 11 percent of known fish species. The oceans have a mean depth of 4000 metres. About 98 percent of the total water volume is below 100 metres, and 75 percent is below 1000 metres.
Marine pelagic fish can be divided into pelagic coastal fish and oceanic pelagic fish. Coastal fish inhabit the relatively shallow and sunlit waters above the continental shelf, while oceanic fish (which may well also swim inshore) inhabit the vast and deep waters beyond the continental shelf. Pelagic fish range in size from small coastal forage fish, such as herrings and sardines, to large apex predator oceanic fishes, such as the Southern bluefin tuna and oceanicsharks. They are usually agile swimmers with streamlined bodies, capable of sustained cruising on long distance migrations.
The Indo-Pacific sailfish, an oceanic pelagic fish, can sprint at over 110 kilometres per hour. Some tuna species cruise across the Pacific Ocean. Many pelagic fish swim in schools weighing hundreds of tonnes. Others are solitary, like the largeocean sunfish weighing over 500 kilograms, which sometimes drift passively with ocean currents, eating jellyfish
Coastal fish (also called neritic or inshore fish) inhabit the waters near the coast and above the continental shelf. Since the continental shelf is usually less than 200 metres deep, it follows that coastal fish that are not demersal fish are usually epipelagic fish, inhabiting the sunlit epipelagic zone. Coastal epipelagic fish are among the most abundant in the world.
They include forage fish as well as the predator fish that feed on them. Forage fish thrive in those inshore waters where high productivity results from the upwelling and shoreline run off of nutrients.
Some are partial residents that spawn in streams, estuaries and bays, but most complete their life cycle in the zone.
Oceanic fish inhabit the oceanic zone, which is the deep open water which lies beyond the continental shelves. Oceanic fish (also called open ocean or offshore fish) live in the waters that are not above the continental shelf. Oceanic fish can be contrasted with coastal fish, which do live above the continental shelf. However, the two types are not mutually exclusive, since there are no firm boundaries between coastal and ocean regions, and many epipelagic fish move between coastal and oceanic waters, particularly in different stages in their life cycle. Oceanic epipelagic fish can be true residents, partial residents, or accidental residents.
True residents live their entire life in the open ocean. Only a few species are true residents, such as tuna, billfish, flying fish, sauries, commercial pilot fish and remoras, dolphin, ocean sharks and ocean sunfish. Most of these species migrate back and forth across open oceans, rarely venturing over continental shelves. Some true residents associate with drifting jellyfish or seaweeds. Partial residents occur in three groups: species which live in the zone only when they are juveniles (drifting with jellyfish and seaweeds); species which live in the zone only when they are adults (salmon, flying fish, dolphin and whale sharks); and deep water species which make nightly migrations up into the surface waters (such as the lantern fish).
Accidental residents occur occasionally when adults and juveniles of species from other environments are carried by accident into the zone by currents
The huge ocean sunfish, a true resident of the ocean epipelagic zone, sometimes drifts with the current, eating jellyfish
The giant whale shark, another resident of the ocean epipelagic zone, filter feeds on plankton, and periodically dives deep into the mesopelagic zone.
Lantern fish are partial residents of the ocean epipelagic zone. During the day they hide in deep waters, but at night they migrate up to surface waters to feed.
Large epipelagic predator fish, like this Atlantic blue fin tuna, have a deeply forked tail and a smooth body shaped like a spindle tapered at both ends and counter shaded with silvery colours. Small epipelagic forage fish, like this Atlantic herring, share the same body features listed for the predator fish above. Epipelagic fish inhabit the epipelagic zone. The epipelagic zone is the water from the surface of the sea down to 200 metres. It is also referred to as the surface waters or the sunlit zone, and includes the photic zone. The photic zone is defined as the surface waters down to the point where the sunlight has attenuated to 1 percent of the surface value. This depth depends on how turbid the water is, but in clear water can extend to 200 metres, coinciding with the epipelagic zone. The photic zone has sufficient light for phytoplankton to photosynthese.
The epipelagic zone is vast, and is the home for most pelagic fish. The zone is well lit so visual predators can use their eyesight, is usually well mixed and oxygenated from wave action, and can be a good habitat for algae to grow. However, it is an almost featureless habitat. This lack of habitat diversity results in a lack of species diversity, so the zone supports less than 2 percent of the world's known fish species. Much of the zone lacks nutrients for supporting fish, so epipelagic fish tend to be found in coastal water above the continental shelves, where land runoff can provide nutrients, or in those parts of the ocean where upwelling moves nutrients into the area.
Drifting Sargassum seaweed provides food and shelter for small epipelagic fish. The small round spheres are floats filled with carbon dioxide, which provide buoyancy to the algae.
Epipelagic fish are fascinated with floating objects. They aggregate in considerable numbers around objects such as drifting flotsam, rafts, jellyfish and floating seaweed. The objects appear to provide a "visual stimulus in an optical void". Floating objects can offer some protection for juvenile fish from predators. The availability of lots of drifting seaweed or jellyfish can result in significant increases in the survival rates of some juvenile species.
Many coastal juveniles use seaweed for the shelter and the food that is available from invertebrates and other fish associated with it. Drifting seaweed, particularly the pelagic Sargassum, provide a niche habitat with its own shelter and food, and even supports its own unique fauna, such as the sargassum fish
DEEP SEA FISH
Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the ocean. The lantern fish is, by far, the most common deep-sea fish. Other deep sea fish include the flashlight fish, cookie cutter shark, bristle mouths, anglerfish, and viperfish. Only about 2% of known marine species inhabit the pelagic environment. This means that they live in the water column as opposed to the benthic organisms that live in or on the sea floor.Deep-sea organisms generally inhabit bathypelagic (1000m-4000m deep) and abyssopelagic (4000m-6000m deep) zones. However, characteristics of deep-sea organisms, such as bioluminescence can be seen in the mesopelagic (200m-1000m deep) zone as well. The mesopelagic zone is the disphotic zone, meaning light there is minimal but still measurable. The oxygen minimum layer exists somewhere between a depth of 700m and 1000m deep depending on the place in the ocean.
In the deep ocean, the waters extend far below the epipelagic zone, and support very different types of pelagic fishes adapted to living in these deeper zones. In deep water, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. Its origin lies in activities within the productive photic zone. Marine snow includes dead or dying plankton, protists (diatoms), fecal matter, sand, soot and other inorganic dust. The "snowflakes" grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor. However, most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres of their journey, that is, within the epipelagic zone. In this way marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems: As sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source.
Some deep-sea pelagic groups, such as the lantern fish, ridgehead, marine hatchet fish, and lightfish families are sometimes termed pseudoceanic because, rather than having an even distribution in open water, they occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes. The phenomenon is explained by the likewise abundance of prey species which are also attracted to the structures
India is blessed with vast inland water resources in the form of rivers, estuaries, natural and manmade lakes. The Inland water bodies have been divided into five riverine systems and their tributaries extending to a length of about 29,000 km in the country - Indus, Ganges, Bramhaputra, East flowing riverine system and West riverine system. All these rivers, their tributaries, canals and irrigation channels have and area of roughly 13000km. These water bodies harbor the original germplasm of one of the richest and diversified fish fauna of the world comprising 930 fish species belonging to 326 genera. The major river systems of India on the basis of drainage can be divided broadly into two major rivers systems. They are (i) Himalayan rivers system (Ganga, Indus and Bramhaputra) and (ii) Peninsular river system (East cost and West coast river system).
Ganges River System:
It is the largest river systems of the world, having a combined length (including tributaries) of 12,500 km. It originates from Gangotri in the Himalayas at a height of about 3129 km above the sea level. After origin it drains the southern slopes of the central Himalayas. Ganga passes through UP, Bihar, some parts of Rajasthan, M.P. and west Bengal and finally joins to the Bay of Bengal. It has a large number of tributaries and ‘Yamuna’ river is one of the major tributaries of this system, which is about 1000 km long. The other tributaries are - Ram Ganga. Gomti, Ghaghra, Gandak, Kosi, Chambal, Betwa and Ken. Further more; it has numerous lakes, ponds and Jheels, both perennial and seasonal areas. It has a total catchment area of 9.71 lakh sq. km and receives an annual rainfall of 25-77 inches.
Fishing gears used :
The principal gears used in Ganga river system are dragnets, cast nets and bag nets.
Godavari River System:
It originates in Doolai hills near Nasik in North Western Ghats. This river system is a part of East coast of pennensular river system, with a length of 1465 km covering the states like Maharastra, Andhrapradesh and Madhyapradesh. It has the primary tributaries like manjira, Wainganga; Subtributaries like paingunga and wardha and minor tributaries like maner and sabari. It drains into Bay of Bengal. It has a total catchments area of over 315,980 sqkm.
i) Temperature - 27.5 to 36.40C
ii) PH - 7.2 to 8.3
iii) Do2 mg/L - 1.26 -18.2
iv) Co2 - 0.0 - 6.6 ppm
v) Bicarbonates - 45.8 -192-2ppm
Fisheries of Godavari River System:
The head waters harbour a variety of game fishes but don’t support the commercial fisheries. The commercial fisheries consist of carps (major caps, Labeo fimbriatus), large cat fish (Mystus spp., Wallago attu; Bagarius bagarius) and fresh water prawn (Macrobrachium rosenbergii). Hilsa formed lucrative -fisheries and the Indian major carps uplanted in the river in the beginning in 19th century are thriving well and contributing to the commercial fisheries.
Fishing gears used:
The principle gear used in Godavari river system are falls under two categories viz. gill nets, which include setgill nets, drift nets, drag gill nets (Benduvala) and the barrier gillnet (Katu vala). Seines include shore seine (Jaruguvala), Large seine (Allui vala) and dragnet castnets are also employed for fishing.
Krishna river system:
The originates in Western Ghats region, south of Poona and finally drains into East coast, with an a length of 1401km covering the state like Maharastra, Karnataka and Andhrapradesh. It has the main tributaries like Bhima (Annual) and Tungabhadra (Perennial). This river system has an total catchments area of 2,33,229 sq km. The physico-chemical characteristics, fish fauna and the fishing gears used similar to the Godavari river system. In general, the physiographic and fish fauna resembles the Godavari river systems. The head waters support rich fishery when compared to mid-stretch, which is rocky and inaccessible. No information is available on its present fishery and catch statistics.
Cauveri river System:
This river system originates from Brahmagiri hills on western ghat, with an elevation of 1340 m extending to a length of 800 km. this river system covering the states the Karnataka and Tamil Nadu finally drains into Bay of Bengal in Thanjavur district of Tamil Nadu. It has the tributaries like Bhavani, Noyil and Amaravathi. This river system has an total catchment area of 4,70000 sq km. The water resources of the river are extensively exploited as numerous reservoirs, anicuts and barrages have been built on the river.
i) Temperature - 26 to 30.90C
ii) PH - 7.6 to 8.5
iii) Do2 mg/L - 1.26 -18.2
iv) Co2 - 0.0 - 6.6 ppm
v) Bicarbonates - 45.8 -192-2ppm