Large tracts of abandoned shrimp ponds remain, unsuitable for most uses because of unfavourably altered soil chemistry and limited dispersal ability of propagules, the World Bank in a recent publication warned.
The publication titled ‘Priorities for Sustainably Managing Sri Lanka’s Marine Fisheries, Coastal Aquaculture, and the Ecosystems that Support Them,’ dated September 2021, but released on the WB website recently said the other biggest environmental impact resulted from locating the water intake and wastewater discharge in the same source near one another.
Hence, the spread of the outbreaks of viral diseases in shrimp farms, namely the white spot disease and the yellow head disease, amply demonstrates the importance of physical planning, environmental regulation and good industry standards for the long-term financial viability and sustainability of the aquaculture industry for it to serve as a cornerstone of rural economic development and poverty reduction, it said.
Additionally, the external costs associated with the removal of coastal habitats, which provide environmental services and maintain ecological balance, for the development of shrimp ponds, were overlooked in project valuation and issuance of industry licences by the Government of Sri Lanka (GoSL) and its allied agencies, the WB report said.
Elaborating on the genesis of the shrimp farm industry, the WB said shrimp farming in Sri Lanka began on the Eastern Coast in the 1970s, however, it was soon abandoned because of the civil conflict.
It however said the industry was later revived in the 1980s along the coastal belt between Chilaw and Puttalam in the North Western Province, where it grew rapidly under the impetus of a rising global demand for shrimp.
Aided by the ample availability of suitable habitat as well as quick access to infrastructure, the industry saw a rapid and uncontrolled growth between 1992 and 1996. Small-scale farmers developed in clusters, encroaching on lagoons, mangroves, mudflats, salt marshes, and coconut estates.
Shrimp production peaked by 1998, with the number of farms reaching 1,400 with over 70 hatcheries, and with a total area of 4,500 hectares. Some enterprises produced 8,000–9,000 kilogrammes per hectare per year, stocked at three–40 shrimp per cubic metre in classical earthen ponds.
This rapid rise however was also followed by a rapid decline due to two major outbreaks of viral diseases, the white spot disease and the yellow head disease, forcing 70-90 per cent of the farms to collapse in a very short time.
In some farms along the Puttalam Lagoon, shrimp mortality reached 100 per cent. Losses due to the white spot disease were valued at Rs 1 billion and the two diseases together caused an approximate 70 per cent drop in export volumes. The resulting financial burden was debilitating on the farmers. Subsequent problems with disease led to the abandonment of many shrimp ponds, leaving behind denuded and unproductive landscapes.
Poor site selection and lack of environmental planning and industry regulation had created ideal conditions for the industry’s downfall. It was further estimated that 47 per cent of all farms, on the average smaller than two hectares, were operating without proper licences.
Large tracts of healthy coastal habitats, such as mangroves, salt marshes, seagrass beds, and mudflats, were converted to shrimp ponds. Around Puttalam Lagoon, for example, more than a third of mangroves have been cleared for shrimp ponds since the early 1990s.
Similar findings emerged from Chilaw Lagoon, where 57 per cent of mangroves have been cleared for shrimp ponds since the 1990s, but by 2006, 75 per cent of these ponds had been abandoned. A study on the loss of salt marshes in Puttalam Lagoon notes a loss of 51 per cent between 1981 and 1992.
Meanwhile, a noteworthy omission in this WB document is the impact of Indian fisher poaching on Sri Lankan fishers.
By Paneetha Ameresekere