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Prawns and Shrimps (Dendrobranchiata Sergestoidea, Penaeidae)
Prawns and Shrimps (Dendrobranchiata Sergestoidea, Penaeidae)
Prawns and shrimps are small aquatic animals belonging to the sub-phylum of Crustaceans, which include other marine animals like Crabs, Lobsters and Crayfish. The Prawns and Shrimps are common names and scientific term, hence the Shrimps and Prawns are often used interchangeably as there is really no universally agreed distinction between them. Shrimps and prawns are found in both brackish and freshwater bodies and are found in virtually all the marine bodies of the world.
They often range in sizes from really minute to quite large, often weighing as much as 15pounds. Shrimps and Prawns are low in calories and are sources of unsaturated fat which makes them good for the human body. Although previously consumed as an exotic food, it is now more commonplace in the diet of man, its increasing consumption amongst the average populace has not reduced its market value as it remains the most valuable sector of the global seafood industry, with a worth of over $18 billion in the year 2002.
Additionally, the sector is also experiencing tremendous growth, with an annual growth rate of 3%. Considering all these factors the future looks bright for Shrimp/Prawn farming.
Source: Daily mail
Shrimp Farming and Production
Shrimps were originally produced from wide capture (artisanal and commercial Shrimp farmers) and traditional Shrimp farming, but these methods of production cannot meet the global demand, as a result of the decline in Shrimps produced through wide capture. In an effort to meet increasing demand, emphasis is being placed on artificial farming and it now accounts for about 50% of global Shrimps production.
Nigeria is one of the countries with abundance natural supply of Shrimps with an annual production of 12,000 metric tons. However, with the decline in global wide capture there is a need to supplement production with Shrimps aquaculture and Nigeria is regarded as a potential frontier in Shrimp farming because of its numerous coastal and mangrove areas.
Shrimp Farming Basics
Shrimp are typically grown in brackish water, Swimming pools and other containers with significant depth are all suitable vessels for raising freshwater shrimp but they do not yield the best results. For the production of large quantities of healthy crustaceans, a pond is more suitable. A female shrimp lays thousands to millions of eggs, which hatch after about a day. The nauplii, as the hatched shrimp is called, are fed algae and brine shrimp nauplii. The nauplii develop into young shrimps after about 12 days, The nauplii can be kept in nurseries before being transferred to the pond or can be kept in an acclimation tank to prepare them for transfer in grow out ponds, such transfer usually occurs around the 25th day. The young shrimp stays in the pond till maturity which spans for about three to six months after hatching, after which they are harvested by either draining the pond or by the use of nets.
Shrimps farming methods
Traditional /extensive method-this is the simplest Shrimp aquaculture approach where Shrimps are farmed with minimum intervention. The farm is situated in coastal or mangrove areas and the seed stock for production is acquired from the wild, as a result the supply is season dependent. The average stocking density is usually low (between 3000-5000fry per hectare) and a yield between 500-800kg/ha/year. The ponds are often irregular in shape and size and fall between 3-20 hectares. In this method, the use of pump is not employed and water exchange is left to tidal action.
Semi-intensive method-In this farming method, the improvement over the traditional approach is in the introduction of a systematic pond configuration. The ponds are generally rectangular in shape with typical sizes of about about 1–3 hectares and water depth of 0.80 to 1.2 meters. Each pond has separate inlet and outlet gates to facilitate water exchange, pond preparation and harvesting. A diagonal ditch, 5–10 meters wide and 30–50 cm deep extending from inlet to outlet is also constructed to facilitate drainage of water and collection of Shrimp during harvest. The ditch also serves as a refuge for the Shrimps during sunny days. This method involves higher stocking rates, use of supplementary feed and the implementation of a regular water management scheme. Current practices vary from country to country. The typical rate of stocking fry for semi-intensive culture operation varies from 20,000 to 50,000 fry per hectare. Supplementary feed is given daily in addition to the existing natural food produced through the application of fertilizers. This operation also requires the use of a water pump to facilitate water exchange.
Intensive Shrimp Farming: this is the most financially rewarding method of Shrimp farming as it promises more yield and more return on investment.
The aim of the intensive Shrimp farming is to hasten the Shrimp growing cycle, to produce Shrimps of uniform size and also to increase yield per hectare. In this farming system, conditions must be controlled to achieve the aforementioned goals.
A farming technology called Galveston or “clear water” hatchery employs intensive control to breed shrimp in industrial scale. Large-scale hatcheries usually augment young shrimp diet of algae with commercial feed. They use big tanks that could hold up to 30 tons.
As conditions are highly controlled, it is possible to produce seed stock all year round and to stock shrimp at higher densities. As it is possible to stock more shrimp per unit area, the pond used could be smaller. In this setup, aeration is needed to keep oxygen supply at the desired level to avoid a situation where shrimps die from lack of oxygen. High water exchange is also necessary in getting rid of wastes materials from the water. Lastly, there is a need for round-the clock monitoring. Survival rates and yield are higher for this kind of farming. Understandably, production cost is also higher.
How to start fresh water Shrimp Business
Establishing a fresh water shrimp business requires some effort and certain factors should be considered before starting up as they determine the eventual success of the business. Some of these important factors are discussed below;
Choosing the right location
The first step in starting a shrimp farm is choosing the location, the location of a Shrimp farm is essential because location affect the survival, growth and yield of Shrimps been farmed. In siting a Shrimp farn, the following are some of the factors to consider;
-Proximity to marine water: Warm, brackish water is required for the cultivation of shrimp; hence, the proximity to ocean water is a prerequisite for starting a Shrimp farm.
-Soil and topography of the area: Soil of the proposed location is of utmost importance. The soil should have enough clayey content to ensure that the constructed ponds can hold water. The soil should also be tested to determine its acidity, level of fertility, amount of organic load and physical composition as these factors play a huge role in the quality and yield of the Shrimps.
-Ease of access to Shrimp larvae: The ease of access to Shrimp larvae reduces the cost of transportation and also reduces the handling stress the animals will be subjected to.
Construction of pond and creation of a suitable ecosystem
In constructing a Shrimp farm, it is necessary to construct two interconnected farms or ponds, this is to aid the convenient transfer of the mature shrimp from one farm to another. In the case of an extensive farm, which is located along a coast or a mangrove, the tides will provide the required water exchange, but in case of an intensive farm located away from the coast, care needs to be taken to keep the water aerated at all times. Most intensive farming practices employ the use of pumps/paddle wheels to keep the oxygen level in the water constant as well as remove impurities, thus ensuring a better yield. Building a gate system for the exchange of fresh ocean water if your farm is located near the ocean makes sense, and it will save you a lot of maintenance headache. For sustainable shrimp ecosystem, the pond should be stocked with algae and phytoplankton: also, the water must always be tested to ensure it is free from harmful bacteria and chemicals before introducing the shrimps. The pH level of the pond must be greater than 6.5 and less than 10 ( although the optimal range is between 7.5 and 8.5); the pond must be free of other animals such as frogs, small fishes etc. which are predators that might prey on the Shrimps.
It should be noted that newly dug ponds yield poor results in the first year due to lack of build-up of algae or insect larvae for the shrimp to feed on, but consequently there will be marked improvement as a result of the gradual buildup of organic matters.
Feeding and feed regulation
Feeding is an essential part of Shrimp farming, as it is needed to ensure that the Shrimps attain a desired harvesting weight within a specified period of time. It is also part of the major cost incurred in shrimp farm business. The shrimps feeding pattern is dependent on the stage of growth of the shrimp and the farming system being used. At the early stage of growth, shrimps can leave on natural food found in the pond, as such fertilization of the pond to initiate build-up of organic materials such as algae and phytoplankton is important. As the Shrimps mature, supplementary feeding is required because their level of food consumption grows and natural food in their habitat becomes insufficient. Common supplement include dry pelleted feed, rice bran, chopped toad and frogs and household leftovers. Supplementary feed can be administered by the use of feeding trays, automatic machine feeder or by broadcasting the feed.
Harvesting the Shrimps
This is the last stage of Shrimp farming. In ideal situations, it is carried out in October - just as it begins to get cooler; thus, stopping the growth period of the shrimp. Mature shrimps can be culled from the pond prior to this time, leaving smaller ones to be harvested or all the shrimps can be harvested at the same time. The shrimps can either be harvested with the use of nets or they can be harvested by draining the pool. Harvesting is best done in the cool hours of the day, this is to prevent the sun from increasing the temperature and decreasing the volume of the water and the oxygen levels in the water which can kill the Shrimps and lose the business revenue.
Opportunities in Shrimp Farming
The market for Shrimps is a global market, as most Shrimps (both farmed and wild capture) are often exported to countries such as Japan, United States of America and Europe. The major producers of Shrimps, especially farmed shrimps are Thailand and Vietnam, both countries battled a disease called Early Mortality Syndrome (EMS) that brought about significant production loss, this loss has further widened the demand-supply gap, creating room for other countries like Nigeria to step in.
As at 2002, Nigeria raked in an income of $56 million from shrimp farming inspite of the low production levels. With increased production, favorable climatic conditions, stall in wild capture and a wide demand-supply gap, there is the potential for an annual income of over $384 million to be generated from Shrimp production making it a most viable and worthwhile venture.
-Chemonics International: ‘Industry Action Plan for Nigerian Shrimps and Prawns’.
-Fisheries Society of Nigeria (FISON)
-N Zabbey, E S Erondu and A I Hart: ‘Nigeria and the prospect of shrimp farming: critical issues’.
-Professor Anetekhai Martins: Dept. of Fish Science, Lagos State University Ojo
-The Nigerian Tribune, tribune.com.ng
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