OP-ED: In-pond raceway system
A climate-smart aquaculture technology
In-pond raceway system or IPRS is a highly sophisticated innovative aquaculture technology, where optimal water chemistry is ensured by maintaining interrupted water flow and waste disposal management,
It eventually allows a suitable environment for super high density fish stocking.
Fishes are stocked in the channels or raceways installed in the pond.
Water chemistry, especially sufficient dissolved oxygen, is supplied round the clock.
In quest of climate change adaptation and growing concern on land and water resources scarcity, this is an environment friendly aquaculture technology that can help to ensure quality and safe seafood for human consumption.
Fish production from IPRS may vary 50-100 Ton/ha, even more depending on species types which is much higher than any other aquaculture systems.
Recent introduction of such an advanced technology in northwestern Chapainawabganj district can be considered as a golden milestone in aquaculture progress and mechanization in Bangladesh.
It also sounds that in near future Bangladesh can play a frontline role in global freshwater aquaculture.
IPRS was first invented in 2005 in Auburn university at Alabama in the USA by a research team headed by Professor Dr. Jesse Chappell and was first introduced in 2007 in a commercial catfish farm.
Thereafter during 2013-14 it was further adopted in China.
This super intensive aquaculture technology was extended in Vietnam, Mexico, India, Egypt and Pakistan in 2016, 2017, 2018, 2018 and 2019 respectively.
In the near future, IPRS technology is going to be introduced in Thailand, Cuba and some other countries of the globe.
Generally, in pond aquaculture fish production is 10-15 metric ton/ha, but with IPRS 50-100m.ton/ha, even more fish production is possible depending on different fish species.
Various types of fish species of different sizes can be cultivated at the same time in the same pond.
Principles of IPRS
Main principle of IPRS is to establish raceways/ channels in a big pond and maintain continuous water flow in those raceways.
Outer area of the raceways is also facilitated by continuous circular water flow.
At the same time, a mechanized feeding system and removal of all waste materials are also ensured.
Sufficient dissolved oxygen supply, continuous water exchange in the raceway and regular removal of pollutants make the system similar to a natural water stream.
Fishes feel convenient, swim freely as they are in their natural home. So they can be cultivated at super high density.
Salient feature of IPRS
Salient features of an IPRS are air-lift, bottom aeration, cells and waste collection arrangements that make this system unique ensuring optimal water chemistry that allows super high density stocking.
White water unit
This unit is the heart of IPRS located at the starting point of the race way.
Its main function is to circulate oxygenated water through the raceway.
In this unit a powerful air lift device or air blower is used that moves the water and passes through the raceway.
Thus water from outside continuously enters the raceway.
At the same time, it works for aeration.
As continuous water flow remains in the channels, fishes get a natural stream like environment so they enjoy spontaneous swimming and their health condition remains good.
Each air lift has a high power (2.2/2.5kw) blower.
With a highest 3kps pressure a blower can generate 230 cubic meter air flow.
There are more than 4 diffuser grids where tube aeration takes place.
In each cell air flow or water flow can be controlled individually thus oxygen supply in each cell is ensured.
This unit has a capacity to pass 15000-liter water per hour through a single cell or raceway that also helps to generate some plankton and beneficial bacteria.
Due to water current organic waste and other solids are accumulated in the waste channel or sludge unit located at the finishing line of the raceway.
Bottom aeration system
At the bottom of each cell there is a separate and independent aeration facility which is known as bottom aeration.
By this system along with horizontal aeration a vertical mixing also takes place that ensures booster aeration in the whole system which makes possible homogeneous water quality in all along the raceway.
High quality blower metal hose, PVC hose, bottom and aero tube aeration tubing are the parts of this system.
Waste collection system
This system acts as a toilet for the fishes where all waste is accumulating and mechanically removed.
This unit is also known as a sludge unit.
A cleaner made of stainless steel, hose and driving system are the main components of this system.
All waste derived from the raceway are accumulated in this unit and then periodically removed outside.
This waste can be used in agricultural crops as organic fertilizer.
These channels or cells made of concrete, permanently fixed at the bottom of the pond, are usually known as raceway.
Fish are stocked in these channels. Usually 3 raceways can be built in 2.0 ha pond area.
In Alabama, USA measurements of the raceways were 7.71m × 4.88m × 1.22m, in Egypt 12.0m × 3.0m ×1.5m, in Campeche, Mexico 5.0m × 25.0m × 1.2m and in Vietnam 25.0m × 5.0m × 2.0m. In our project this measurement is 25m× 5m× 2.5m.
To feed the fish demand or smart feeder is set at the outset of each raceway.
Feeding also can be done manually.
But auto feeding is better than manual feeding, as proper or homogeneous distribution of feed and proper hygiene only can be maintained by smart feeders.
Internet control system
Through the internet, control system implementation of all major activities including monitoring can be done.
Electricity is the lifeline of an IPRS.
It is a completely energy dependent technology.
As fishes are stocked in super high density so the total system can collapse if electricity fails even only for an hour.
So three layered energy supply security should be ensured.
In alternate electricity options oxygen supply is carried on so that emergency treatment can be done in case of diseases.
Because in this case water flow is stopped but oxygen supply remains uninterrupted.
As a result, if necessary medication is possible in treatment.
Besides these there are four powerful air lifts fixed at the four corners of the pond by which a gentle water flow is continued through the whole pond.
Some extra aerators are set up at suitable locations of the pond that supply continuous oxygen and remove noxious gases.