Window-pane Oysters on the verge of extinction in Goa

 Harvesting window-pane oysters has been a traditional livelihood for the fishing community in Zuari river estuary in Goa.  Besides a livelihood source, window-pane oysters were the basis of a thriving cottage industry. Today due to indiscriminate marine infrastructure, water pollution, overfishing and changing natural habitat, this precious marine resource has almost become extinct in most of its traditional habitat areas, except in a single bay at Chicalim, where indiscriminate exploitation is threatening its very brooding stock.

Besides being a livelihood source for innumerable families of the fishing community, window-pane oysters were the basis of a thriving cottage industry in Goa.  For more than 400 years during Portuguese in Goa, window-pane oyster shells were exported to Brazil.  The oyster shells were extensively used in Goa as window-panes at a time when glass was not yet popularly used. Later houses of aristocratic families and well-off families typically used the shiny translucent oyster shells to decorate window panes despite the availability of glass.  Shells of these bivalves were also used to make handicrafts like lampshades, jewellery, while the occasional pearls found within the oysters were used in traditional medicine.

But all that is turning into history now.  Says Dr. Baban Ingole, senior marine scientist at Panaji-based National Institute of Oceanography ”  Mushrooming of shipyards, water pollution and unrestricted fishing has changed the natural habitat of this bivalve.  Despite being declared as a Schedule IV species under the amended Protection of WilldLife Act, 1972, and despite a ban on its commercial exploitation by the Ministry of Environment & Forests, unrestricted harvesting  continues at Chicalim, its only habitat area,  which threatens the very brooding stock of this precious marine resource.  Its limited occurance  and  restricted distribution demands strict regulations on its harvesting”

Window-panes oysters take about 4-5 yrs to mature fully when their muddy brown shells turn translucent white. The flat part of the shell is cut to fit into wooden window pane frames  traditionally  used  in Goan homes. “Warmer waters due to global warming  and increasing acidification of the oceans due to increased carbon emissions may have contributed to changing natural habitat and their proliferation.  Increasing water pollution and extensive marine infrastructure like shipyards and ports have certainly affected their growth profile” says Dr. Ingole.

However there is a silver lining to the story – the Chicalim Villagers Action Committee (CVAC) are demanding governmental action to  save the ‘manvi’ as the oysters are locally called.  Says Rui Araujo, Secretary, CVAC, ” We are not demanding a complete ban on harvesting the oysters, but strict harvesting regulations and the declaration of Chicalim Bay as a non-industrial area”

The strategy is likely to save the brooding stock at Chicalim bay and also ensure sustainable harvesting, thus saving both the livelihood of numerous families as well as this   marine resource from extinction.