Methods of fish farming. Fish farming is the
commercial production of fish, usually in tanks or enclosures,for the
purpose of human consumption. the most important fish species used in
fish farming includes carp, salmon, tilapia and catfish.in fish farming,
natural members is generally referred to as a fish hatchery.
the
pesistent increase in the damand of fish and fish protein,have resulted
to overfishing in wild fishing.fish farming have been a good alternative
to provide fish consumers with enough fish to eat. fish farming is also
another alternative to fish marketers.However, farming carnivorous
fish, such as salmon, does not always reduce pressure on wild fisheries,
since carnivorous farmed fish are usually fed fishmeal and fish oil
extracted from wild forage fish.
Two categories of fish aquaculture
the two
major categories of aquaculture includes
1)extensive aquaculture
2)intensive aquaculture
extensive
aquaculture based on local photosynthetical production and intensive
aquaculture, in which the fish are fed with external food supply.
In
extensive aquaculture the major problem to the fish growth is the
unavailablility of adquate food supply by natural sources, commonly
zooplankton feeding on pelagic algae or benthic animals, such as
crustaceans and mollusks. Tilapia species filter feed directly on
phytoplankton, which makes higher production possible. The
photosynthetic production can be increased by fertilizing the pond water
with artificial fertilizer mixtures, such as potash, phosphorus,
nitrogen and micro-elements. Because most fish are carnivorous, they
occupy a higher place in the trophic chain and therefore only a tiny
fraction of primary photosynthetic production (typically 1%) will be
converted into harvest-able fish.
Another issue is the risk of
algal blooms. When temperatures, nutrient supply and available sunlight
are optimal for algal growth, algae multiply their biomass at an
exponential rate, eventually leading to an exhaustion of available
nutrients and a subsequent die-off. The decaying algal biomass will
deplete the oxygen in the pond water because it blocks out the sun and
pollutes it with organic and inorganic solutes (such as ammonium ions),
which can (and frequently do) lead to massive loss of fish.
In
order to tap all available food sources in the pond, the aquaculturist
will choose fish species which occupy different places in the pond
ecosystem, e.g., a filter algae feeder such as tilapia, a benthic feeder
such as carp or catfish and a zooplankton feeder (various carps) or
submerged weeds feeder such as grass carp.
In the intensive
systems fish production per unit of surface can be increased at will, as
long as sufficient oxygen, fresh water and food are provided. Because
of the requirement of sufficient fresh water, a massive water
purification system must be integrated in the fish farm. A clever way to
achieve this is the combination of hydroponic horticulture and water
treatment, see below. The exception to this rule are cages which are
placed in a river or sea, which supplements the fish crop with
sufficient oxygenated water. Some environmentalists object to this
practice.
The cost of inputs per unit of fish weight is higher in
intensive fish farming than in extensive fish farming, especially
because of the high cost of fish feed, which must contain a much higher
level of protein (up to 60%) than cattle food and a balanced amino acid
composition as well. However, these higher protein level requirements
are a consequence of the higher food conversion efficiency (FCR—kg of
feed per kg of animal produced) of aquatic animals. Fish like salmon
have FCR's in the range of 1.1 kg of feed per kg of salmon[citation
needed] whereas chickens are in the 2.5 kg of feed per kg of chicken
range. Fish don't have to stand up or keep warm and this eliminates a
lot of carbohydrates and fats in the diet, required to provide this
energy. This frequently is offset by the lower land costs and the higher
productions which can be obtained due to the high level of input
control.
Aeration of the water in fish farming
Aeration
of the water, as fish need a sufficient oxygen level for growth. This
is achieved by bubbling, cascade flow or aqueous oxygen. Catfish,
Clarias spp. can breathe atmospheric air and can tolerate much higher
levels of pollutants than trout or salmon, which makes aeration and
water purification less necessary and makes Clarias species especially
suited for intensive fish production. In some Clarias farms about 10% of
the water volume can consist of fish biomass.
The risk of
infections by parasites like fish lice, fungi (Saprolegnia spp.),
intestinal worms (such as nematodes or trematodes), bacteria (e.g.,
Yersinia spp., Pseudomonas spp.), and protozoa (such as Dinoflagellates)
is similar to animal husbandry, especially at high population
densities. However, animal husbandry is a larger and more
technologically mature area of human agriculture and better solutions to
pathogen problem exist. Intensive aquaculture does have to provide
adequate water quality (oxygen, ammonia, nitrite, etc.) levels to
minimize stress, which makes the pathogen problem more difficult. This
means, intensive aquaculture requires tight monitoring and a high level
of expertise of the fish farmer.
water quality
Control of
water quality is crucial. Fertilizing, clarifying and pH control of the
water can increase yields substantially, as long as eutrophication is
prevented and oxygen levels stay high.Yields can be low if the fish grow
ill from electrolyte stress.
Composite fish culture
The
Composite fish culture system is a technology developed in India by the
Indian Council of Agricultural Research in the 1970s. In this system
both local and imported fish species, a combination of five or six fish
species is used in a single fish pond. These species are selected so
that they do not compete for food among them having different types of
food habitats.[8][9] As a result the food available in all the parts of
the pond is used. Fish used in this system include catla and silver carp
which are surface feeders, rohu a column feeder and mrigal and common
carp which are bottom feeders. Other fish will also feed on the excreta
of the common carp and this helps contribute to the efficiency of the
system which in optimal conditions will produce 3000–6000 kg of fish per
hectare per year.
One of the largest problems with freshwater
pisciculture is
that it can use a million gallons of water per acre (about 1 m³ of
water per m²) each year. Extended water purification systems allow for
the reuse (recycling) of local water.
The largest-scale pure fish
farms use a system derived (admittedly much refined) from the New
Alchemy Institute in the 1970s. Basically, large plastic fish tanks are
placed in a greenhouse. A
hydroponic bed
is placed near, above or between them. When tilapia are raised in the
tanks, they are able to eat algae, which naturally grows in the tanks
when the tanks are properly fertilized.
The tank water is slowly
circulated to the hydroponic beds where the tilapia waste feeds
commercial plant crops. Carefully cultured microorganisms in the
hydroponic bed convert ammonia to nitrates, and the plants are
fertilized by the nitrates and phosphates. Other wastes are strained out
by the hydroponic media, which doubles as an aerated pebble-bed filter.
feed in fish farming
The
issue of feeds in fish farming has been a controversial one. Many
cultured fishes (tilapia, carp, catfish, many others) require no meat or
fish products in their diets. Top-level carnivores (most salmon
species) depend on fish feed of which a portion is usually derived from
wild caught (anchovies, menhaden, etc.). Vegetable-derived proteins have
successfully replaced fish meal in feeds for carnivorous fishes, but
vegetable-derived oils have not successfully been incorporated into the
diets of carnivores.
Secondly, farmed fish are kept in
concentrations never seen in the wild (e.g. 50,000 fish in a 2-acre
(8,100 m2) area. with each fish occupying less room than the average
bathtub. This can cause several forms of pollution. Packed tightly, fish
rub against each other and the sides of their cages, damaging their
fins and tails and becoming sickened with various diseases and
infections. This also causes stress.
Other potential problems faced by
Aquaculturists
are the obtaining of various permits and water-use rights,
profitability, concerns about invasive species and genetic engineering
depending on what species are involved, and interaction with the United
Nations Convention on the Law of the Sea.
In regards to
genetically modified farmed salmon, concern has been raised over their
proven reproductive advantage and how it could potentially decimate
local fish populations, if released into the wild. Biologist Rick
Howard did a controlled laboratory study where wild fish and GMO fish
were allowed to breed. The GMO fish crowded out the wild fish in
spawning beds, but the offspring were less likely to survive. The
colorant used to make pen-raised salmon appear rosy like their wild
cousins has been linked with retinal problems in humans.
For more information on fish farming call mr ifeanyi 07062626974 or visit more posts on newsworldng.com
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