Types of aquaculture : agri learner

Types of aquaculture

1. Fish culture in Ponds

Pond systems

It is the most common method of fish culture. Water is maintained in an enclosed area by
artificially constructed ponds where the aquatic animals such the finfish and shellfish are reared.
The ponds may be filled with canal water, rain water, bore well water or from other water sources.
The pond must be constructed after proper site selection. The climate, topography, water
availability and soil quality of the region influence the character of the fish pond.
Based on these factors, ponds are primarily of two types, namely,
1. Watershed pond
2. Levee Pond

Watershed Pond Systems

For watershed ponds, water required to fill and maintain the pond water is entirely sourced
from the watershed runoff, though groundwater (bore well) and surface water (stream and
reservoirs) can be used as additional water sources.
The major factors to be considered are soil type, characteristics, topography and water supplies.
· The soil type influences how well the ponds will hold water; mud and mud-silt type soils
are preferred for pond construction because it prevents leakage. The good quality soil containing a
lower limit of 20 percent clay is necessary for making ponds.
· The topography determines the size and shape of the ponds. The watershed ponds should
not be more than 10 feet deep. The size of the ponds should be less than 20 acres for better
management. Sites, where huge individual ponds could be built, can be divided into smaller ponds
built in series.
· The availability and quality of water determine where and what type of pond should be
made. Growing and harvesting are more challenging in watershed ponds than levee ponds due to
erratic water supplies, uneven bottom and side, and size and excessive depth of the dugout.
· Advantages of this pond system include Construction of Pond is inexpensive, free water is
available and there is less competition for water from other agriculture activities.

Levee Pond Systems

Levee ponds are created in flat land areas where there is inadequate water to fill the ponds from the watershed. The groundwater is typically used to fill the ponds.Prior to building of ponds make sure whether the site is suitable for pond construction by looking at the characteristics of soil type, quality and ground water availability. The type of soil influence the pond productivity and life expectancy. It is necessary to have 20 percent of clay in the soil to prevent the leakage of the pool.

2. Cage culture in Aquaculture

Today cage culture is receiving more attention by both researchers and commercial
producers. Factors such as increasing consumption of fish, declining stocks of wild fishes and poor
farm economy has increased interest in fish production in cages. Many small or limited resource
farmers are looking for alternatives to traditional agricultural crops. Aquaculture appears to be a
rapidly expanding industry and it offer opportunities even on a small scale. Cage culture also offers
the farmer a chance to utilize existing water resources in which most cases have only limited use for
other purposes.

NOTE:

The right choice of site contributes significantly in the success of cage farm. Site selection
is vitally important since it can greatly influence economic viability by determining capital outlay,
by affecting running costs, rate of production and mortality factors.
Ÿ Site selection is a key factor in any aquaculture operation, affecting both success and
sustainability.
· Circular cages of different diameter ranging from 2 m to 15 m, designed for the culture of fishes
such as milkfish, mullet, cobia, pompano, sea bass, pearl spot, shellfishes such as shrimps, crabs
and lobsters were experimented and demonstrated successfully in India by Central Marine
Fisheries Research Institute (CMFRI).
· Stocking of right sized fish juveniles in adequate stocking density is another factor which
determines the success of farming. The stocking density and size of stocked fishes varies with
different species.
· Proper feeding of quality feeds, periodic monitoring and cleaning of cages contributes
immensely to the success of cage farming.
· With proper management of cage erected at an ideal location can yield a production of 20-
40kg/m 3 with various species of fishes.

3. Biofloc culture

It is an innovative and cost-effective technology in which toxic materials to the fish and
shellfish such as Nitrate, Nitrite, Ammonia can be converted to useful product, ie., proteinaceous
feed. It is the technology used in aquaculture system with limited or zero water exchange under
high stocking density, strong aeration and biota formed by biofloc.The culture of biofloc will be
productive in the case of culture tanks exposed to sun.

Biofloc system – the need
Biofloc system was developed to improve the environmental control over the aquatic
animal production. In aquaculture, the strong influential factors are the feed cost (accounting to
60% of the total production cost) and most limiting factor is the water/land availability. High
stocking density and rearing of aquatic animals requires wastewater treatment. Biofloc system is a
wastewater treatment which has gained vital importance as an approach in aquaculture.
The principle of this technique is the generation of nitrogen cycle by maintaining higher C:
N ratio through stimulating heterotrophic microbial growth, which assimilates the nitrogenous
waste that can be exploited by the cultured spices as a feed. The biofloc technology is not only
effective in treating the waste but also grants nutrition to the aquatic animal.
The higher C : N is maintained through the addition of carbohydrate source (molasses) and
the water quality is improved through the production of high quality single cell microbial protein.
In such condition, dense microorganisms develop and function both as bioreactor controlling water
quality and protein food source. Immobilization of toxic nitrogen species occurs more rapidly in
bioflocs because the growth rate and microbial production per unit substrate of heterotrophs are
ten-times greater than that of the autotrophic nitrifying bacteria. This technology is based on the
principle of flocculation within the system.

The biofloc technology has been implemented in shrimp farming due to its bottom
dwelling habit and resistance to environmental changes. Studies have been conducted to assess the
larval growth and reproductive performance of shrimps and Nile tilapia. An improved breeding
performance was observed in shrimp reared in the biofloc system when compared to that of normal
culture practices. Similarly improved larval growth performance was also noticed.

Composition and nutritional value of biofloc
Biofloc is a heterogeneous aggregate of suspended particles and variety of microorganisms associated with extracellular polymeric substances. It is composed of microorganisms such as bacteria, algae, fungi, invertebrates and detritus, etc. It is a protein-rich live feed formed as a result of conversion of unused feed and excreta into a natural food in a culture system on exposure to sunlight. Each floc is held together in a loose matrix of mucus that is secreted by bacteria and bound by filamentous microorganisms or electrostatic attraction. Large flocs can be seen with the naked eye, but most of them are microscopic.

Floc size range from 50 – 200 microns. A good nutritional value is found in biofloc. The dry weight protein ranges from 25 – 50 percent, fat ranges 0.5 – 15 percent. It is a good source of vitamins and minerals, particularly phosphorous. It also has an effect similar to probiotics. The dried biofloc is proposed as an ingredient to replace the fishmeal or soybean in the feed. The nutritional quality is good; however, only limited qualities are available. Furthermore, the cost-effectiveness of producing and drying biofloc solids at a commercial scale is a challenge.