Due to the enormous nutritional value with extraordinary taste, ability to prepare to suit any cuisine, not having any cultural taboos and with excellent health benefits have contributed to the unparalleled demand for shrimp in the present world as an irreplaceable food commodity.
The incredible demand for this unique product has resulted in the popularisation of shrimp farming, though the same product is caught from the mighty ocean as a natural product.
It is never an exaggeration of the said demand, since a basic principle of economics has been proved wrong by this specific food item. This is because, when the shrimp supply increases, the retail price also increases, since housewives who go to the market are compelled to buy this product once they see the eye-catching shrimp heaps available for marketing, even though this was never an item in the list.
Since it is a fact that Asians were always eating the tastiest food, this habit would have led to the commencement of shrimp aquaculture in Southeast Asia more than 600 years ago. Though shrimp farming originated in Southeast Asia, commercial shrimp farming showed rapid growth since the 1960s.
The first landmark momentum in shrimp farming technologies occurred in Japan in the late 1930s, along with the understanding of the complete life cycle of the shrimp, which resulted in successful induced spawning for the first time in the world and rearing of larvae in millions for culture purposes.
Though, World War II had an impact on the further development of the technique, within two decades following the war, it was developed more with appropriate techniques for larval rearing and grow-out phases, which remain the basis of shrimp farming technology.
Initially, these technological inventions were transferred to other countries such as the United States and Taiwan. Meanwhile, finding the more favourable climates, greater availability of land resources and identification of more suitable species led to the present level of development of this business.
Today, owing to the huge demand and million-dollar profit margin, shrimp farming is expanding rapidly and shrimp products are placed second among the most traded aquaculture produce. Globally, shrimp production has increased by 18 percent compared to that in 2017, while over 3.4 million tons of shrimp harvest is marketed each year at an estimated wholesale price ranging between US$3,800 and 8,800 per MT.
Shrimp production in the world has now been increased up to 4 million MT, compared to around 1.7 million MT produced in 1980, where about 80 percent of world shrimp culture production comes from the Asian countries.
Shrimp farming and current status in Sri Lanka
Being a South Asian country, Sri Lanka also embraced the regional trend of culturing Black Tiger shrimp (Penaeus monodon) in the late 1970s on the Eastern coast of the island by four large-scale multi-national companies and a few medium-scale entrepreneurs, however, without the involvement of the Government.
With the onset of terrorism in the country in the early 1990s, this venture got shifted to North-Western province. Blessed with estuaries, lagoons, mangrove swamps, tidal flats and freshwater resources such as Kala-Oya, Ma-Oya and Modaragam, together with the unique extensive area formed as a result of the Dutch canal carrying brackish water in the supra-tidal zone were the main reasons for this shift.
Retired public servants, private companies and those who had money and guts to invest in a risky venture including those who had political influence were the main entrepreneurs.
The courage to take risk in investing in this new business venture, ability to invest a few million rupees (those days of course), and having the capacity to acquire a few hectares of private or Government land were the only limitations for these entrepreneurs.
However, those limitations were not able to limit the number of investors, since finally around 1,400 farms were established in such a short period of time in the North-Western province, without any scientific basis and in an uncontrollable manner.
Nevertheless, though unscientific, this development finally made the shrimp industry to become one of the main constituents in fisheries export products and around 50 percent of the total export earnings from fisheries came from this industry in the mid 1990s.
The extent of the unscientific investments could be easily explained, since the outlet of one farm (which carried polluted water) was the inlet of the adjoining farms. Necessity of the scientific basis for these aquaculture systems was proved by the eruption of different shrimp diseases immediately, finally completely devastating the industry even faster than the commencement.
The up and downtrend as indicated in the figure 1, which has been published by the National Aquaculture Development Authority (NAQDA) in 2021 indicating the annual shrimp production of Sri Lanka over the years, clearly testify the disease influence on the production and proves beyond any doubt the mandatory role of scientific methodology in human investments.
Through semi-intensive farming, vast areas were deprived of beneficial mangroves, at the same time pumping enormous quantities of protein-rich feeds as well as excreta. With time, the unavailability of the natural cleaning process powered by mangrove vegetation, led to culturing of shrimps in polluted waters, which resulted in inevitable disease prevalence, finally with the almost total drastic collapse of shrimp farming in the 1990s.
During 1988–1990, 1996 and 1998, Sri Lanka witnessed three significant shrimp disease outbreaks due to the epizootic viral diseases, namely, Monodon Baculovirus (MBV), White spot syndrome virus and Yellow-head virus respectively, each of which resulted in the industry’s massive collapse.
Emergence of White-spot virus disease in 1996 caused losses of SLR 1,000 million. In 1998, due to the Yellow-head virus epidemic, about 85 percent of farms were abandoned, which resulted in approximately 70 percent drop in exports.
However, Sri Lanka has been gradually growing its shrimp farming industry in a favourable direction since 2004 and in 2019, has exported 1780.5 MT of shrimps with a value of SLR 3.235 million, the details of which are shown in figure 2 as published by NAQDA in 2021.
Detrimental effects of shrimp farming
Shrimp farming is not an exception to the rule “nothing is perfect in this world”. That means everything has both advantages as well as disadvantages. Therefore, due to different reasons as stated below, disadvantages of shrimp farming appeared even in Sri Lanka, which extends from economic to environment-based factors.
Socio-economic factors
Ignoring rational farming practices to maximise profits has been a major course for the spread of diseases that has led to considerable economic losses. Stocking shrimp in higher densities and moving for an extra cycle than the recommended, significantly contributed to spread of diseases mainly due to pollution of water.
This condition often got aggravated, since the majority of the farmers directly discharged the used water to the common waterways, by not using the sedimentation tanks, which were constructed solely for purification purposes of this polluted water.
As the bulk of the processed shrimp is eaten mostly by the rich, who often munch instead of eating, feeding pattern of shrimps has become the same. This munching behaviour has caused enormous difficulties to the culturists, as only around 40–60 percent of feed is consumed by the shrimps in water circulating culture systems.
Protein-rich, expensive feed must be available whenever a shrimp needs, as otherwise, it will predate on the weaker, since they are cannibalistic. This has resulted not only in making shrimp culture expensive, but also cultured water becoming excessively polluted.
Non-use of suitable nets for filtering the incoming water to culture ponds led to the entry of wild fish and other animals, which carried different pathogens, thus causing disease to the cultured shrimp.
Irrational water management due to different reasons including aforesaid incorrect and irrational culture practices eventually led to the pollution of water in the aquatic resources, whose water was used in culture ponds.
Addressing excessive application of different organic and inorganic chemicals such as antibiotics and pesticides for shrimp farming purposes, which are finally released to the common waterways, has led to the pollution of the entire aquatic resources including canals and lagoons.
This has caused a significant impact on both biotic and abiotic ecosystems, thereby directly affecting the fish production in these resources. Finally, this also has caused hardships to local fishermen and others, mainly due to a reduction in fish production, who were directly using these resources for their livelihood and this was a common experience even in Sri Lanka.
The challenges faced by the native people are a long list. Since private farms recruited most of their staff including workers from outside due to different reasons, the pains of the locals can be understood easily.
Some of their fishing areas including mooring facilities for their fishing crafts were completely lost due to shrimp farming, thereby affecting even the living conditions and earnings. In addition, once these common pool resources were “privatised”, the physical and mental pains experienced by the local community are also not difficult to visualise.
In addition to the low fish production, the construction of shrimp farms all over the area led to the closure of traditionally used access roads, which were used not only for daily activities but also for easy movement to boat anchoring places and their cultivation. Not only adults but also children were affected as they lost most of their playgrounds (as well as access roads), which disrupted early childhood development.
Salinisation of their agricultural lands and drinking water supplies, damages caused due to flooding as a result of obstructions to canals and streams led to conflicts with the investors. These activities led to poor earnings due to loss of resources, loss of freedom mainly due to residing of outsiders in their territories and affected their day-to-day living and socio-cultural factors.
Ecological concerns
Shrimp farms are mostly abandoned due to operational, economic and hygienic issues, and the soil of those farms remains hyper-saline, acidic and degraded.
As a result, these farmlands cannot be used for other purposes such as agriculture, without following an unbearable restoration procedure and will remain the same for a longer period.
In addition, lime and other chemicals used in aquaculture to remediate the soil have changed their physico-chemical properties, thus exacerbating the problem. e.g., of the 1,140 ha of coastal lands in the Puttalam District, which were utilised for shrimp farming, today 90 percent are unproductive. Abandoned ponds could not be utilised even for extensive agriculture practices and only a marginal percentage of lands located in the supra-tidal zone have been converted into coconut plantations. In addition, about 10 ha have been converted into saltpans.
The precious mangrove forest system has been severely affected in the island due to those unplanned, poorly managed, illegal as well as irrational shrimp farming. Those entrepreneurs who were interested in shrimp farming utilised cheaply available intertidal zone resources extensively to establish their shrimp farms, which were the mangrove areas.
The most significant damage to the mangrove ecosystem in the Puttalam district was during the 1992–1998 period, where more than 50 percent of mangroves had been used for shrimp aquaculture. According to available records, between 1998–2000 periods, 13.71 km of mangrove forests had been destroyed due to the construction of shrimp ponds.
Indispensable mangrove forests provide various food resources (critical in the coastal aquatic food chains), breeding grounds, shelter and protection for many aquatic faunas, especially to fin-fish as well as shell-fish species and hence are priceless assets to subsistence and commercial fisheries. Thus, the destruction of mangrove forests has significantly affected traditional fish farming and has severely affected the entire brackish water ecosystem.
Moreover, mangrove vegetation offers many more benefits such as providing breeding grounds for birds and other wild fauna including reptiles and mammals, acting as a carbon sink, purification of water and protecting against salt intrusion, protection of nearby beaches and coral reefs, supplying nutrient resources and land stabilisation, acting as a physical barrier against the high energy waves such as tsunami and storm surges during the extreme weather conditions and thereby protect the coastlines and human settlements.
In addition, mangroves also provide enormous benefits to the local people by supplying firewood, edible plant parts, construction material, medicinal and other non-timber forest products.
However, due to different reasons including unscientific farming, aforementioned invaluable benefits of mangrove forests had been ignored.
Rather than the mangrove forests, destruction of other ecologically sensitive habitats such as lagoons, estuaries and mudflats also have been recorded due to the irrational shrimp farming practices. If the same shrimp culture methodology is extended to other parts of the island, it will lead to an inestimable disaster in Sri Lanka.
For example, release of used water from shrimp farms into the natural ecosystems, which always include pathogen intact feces, will lead to destruction of entire brackish water resources as well as highly productive coastal resources.
Nutritionally enriched effluent can cause eutrophication to the natural water bodies, where such incidents have been often reported in intensive shrimp farming countries like China, Brazil and Bangladesh.
Eutrophication causes the development of harmful algal blooms (HAB), which contributes to biodiversity losses and is now becoming a global concern. The formation of HAB with the mass accumulation of cyanobacteria leads to the release of cyanotoxins, which are extremely toxic to the aquatic fauna as well as flora and ultimately lead to biological desertification.
Strategies to overcome the present disastrous situation
As emphasised above, unscientific and improper management strategies are the main reasons for the irreparable environmental damage, which has taken place in the entire shrimp farming areas of Sri Lanka.
In addition, poor enforcement of the existing regulations has significantly contributed to this damage, especially to the mangrove resources. Responsibility of managing the adjoining mangrove reserves present in each and every shrimp farm as a buffer zone should be handed over to the specific shrimp farm management and strict monitoring of it by the authorities is an easy and effective means in safeguarding these mangrove resources. Adhering to Environment Impact Assessment (EIA) and science-driven Ecological Risk Assessment (ERA) procedures must be strictly monitored, without any bias, irrespective of the farm size.
Irrational semi-intensive farming has become the method to culture shrimp in Sri Lanka, though it welcomes viral diseases, since complete eradication of the virus is not on the agenda, yet.
The present culture method of managing these viral diseases without complete eradication is a high-risk venture. As adult shrimp live under natural conditions in crystal clear offshore waters in the oceans at very low densities, farming them in polluted waters having carriers of pathogens and in extremely high densities is a desperate attempt.
On the other hand, the immense land area, which must be utilised under semi-intensive farming, which is the main cause for the destruction of significant areas of invaluable mangrove resources, is another factor to be considered.
Already, this industry has extended to the Mullaitivu District and other areas of the Batticaloa District in the same manner as commenced in the Chilaw area, utilising extensive areas of inter-tidal zone destroying mangroves.
Destruction of wild-life protected areas for shrimp farming is a common news item. In addition, semi-intensive shrimp farming requires resources in vast amounts, resulting in low productivity and profitability.
Mandatory
Attempting to popularise Litopenaeusvannamei (formerly Penaeusvannamei) instead of Penaeus monodon, could be a great movement taken by Sri Lanka recently, as it allows to get a higher harvest and income owing to lower production cost and less land and water need due to excessively high stocking densities possible, to get an optimum harvest compared with P. monodon.
Nevertheless, the mandatory disease prevention steps, if not taken, would lead to disease outbreaks, which has already been recorded worldwide, even with aquaculture of L. vannamei, as they are also susceptible to bacterial and viral infections once tamed to the pond environment.
The main cause for the disease outbreaks is associated with the essential intensified cultivation systems, which physically as well as physiologically cause stress due to higher density along with differences in salinity, temperature, and dissolved oxygen concentrations compared with the natural systems, which always enhance disease susceptibility.
Black gill, IHHNV (Infectious Hypodermal and Hematopoietic Necrosis Virus), White muscle, White gut and Muscle cramp syndrome have been recorded as the major diseases in Indian L. vannamei farming, and hence mandatory preventive steps must be taken, since P. monodon culture was seriously affected due to transfer of pathogens, which were present in post-larvae brought from India.
White fecal matter syndrome is one of the diseases that Sri Lanka never witnessed and there is sufficient potential to introduce such pathogens to the local culture systems. This disease causes death of P. monodon and all other crustaceans likely to be prone to the infection.
The continued importation of post-larvae of L. vannamei is a matter of concern, and it is essential to take appropriate steps to overcome this, especially with proper coordination with different institutes of the same ministry, which is a primary cause of the poor management observed in Sri Lanka at large. In order to reduce the prevalence of the disease, NAQDA has laid several managerial strategies including mandating the assessment of post-larvae quality.
However, the adapted procedures are questionable, mainly because the same criteria were applied to quality asses P. monodon post-larvae as well. L. vannamei being another species, the physiological differences may require entirely different criteria for the prevention of disease conditions and therefore the application of methods suitable for P. monodon may not be effective.
Hence, correct quality assessment methods and implementation of latest guidelines identified in the world must be experimented and suitably applied urgently, before it is too late. As random sampling methods have failed in this scenario, it is essential to have efficient, but scientific and simplified methodologies to detect the disease-causing pathogens.
Therefore, immediate steps must be taken through proper coordination among the different organisations involved in this lucrative business venture and reap the much needed foreign exchange, while causing minimum environmental pollution with the least use of lands, through the application of super-intensive technologies observed in the world. Adoption of such a system in Sri Lanka would be the only path to solve the present socio-economic problems observed in shrimp farming and to gain the much needed foreign exchange.
A.K. Hasith Priyashnatha
Eastern University, Sri Lanka
Udeni Edirisinghe
Postgraduate Institute of Agriculture/Science, University of Peradeniya, Sri Lanka