The Unwritten Rules of Oyster Fishing

For World Ocean Day, Aaron Savio Lobo studies the fascinating rules of oyster fishing, and the surprising role they play in creating a more sustainable future .

If there is one thing the COVID-19 pandemic has exposed, it is our heavy reliance on the global food network and the ease with which it can break down. It has also given us the opportunity to reflect on how our food is produced, and the cost (most often hidden) of its production. This is particularly true for the seafood sector which has been globally marred by overfishing, human-rights violations and the wanton destruction of marine ecosystems. Sourcing locally has never been more important than it is today. However, most of our local, traditional food systems will struggle to meet the demand if not adequately strengthened and incentivised.

Summers in Goa are typically shellfish months — a time to enjoy the diversity of clam, mussels and oysters, grown and matured to full size. As May heats up and urraq (the lighter and fruitier version of cashew feni) drinking is at its peak, I especially look forward to eating calvam (oysters) and shinaneo (green mussels). I must confess that while I love the Goan style — rawa fried shinaneo — I am not a huge fan of Goan oyster bhaaji, which I find to be overpowered by xacuti masala. I resort to cooking oysters myself.

Both oysters and mussels are available in plenty at the numerous fish markets in the state during this season, but I prefer to go straight to the source — Pradip’s home along the Nerul creek. Pradip and his family have been harvesting oysters for years now, and usually sell them at the Nerul market, or near the bridge.

Freshly shucked plump Brackish river oysters

Harvesting Oysters
In Goa, while both men and women are involved in harvesting oysters, there is typically a difference in the way they do it. Women can be seen chipping for hooded oysters (Saccostrea cucullata) with their sickles, on the exposed rocky rubble at low tide; while the men paddle out in their canoes with long bamboo poles, into the deeper waters of the creek, inhabited by the large Brackish water oyster (Magallana bilineata). They then push their poles into the creek’s soft floor, which supports them as they lower themselves several feet below, to the bottom of the creek. Here, they sift through the soft sediments with their hands, emerging every couple of minutes with one or two large oysters. They use gloves to protect themselves from the razor-sharp oyster shells, which are often further encrusted with other oysters and barnacles. To make sure the oysters are alive and full, they tap the shell on the sides of their canoes. A hollow sound indicates they are dead and empty — therefore, to be discarded. They do occasionally bring up entire rocks — an oyster cluster! And if they get lucky, discarded car tyres encrusted with 20 or more large oysters. Paradoxically, this trash also serves as a substrate onto which the oyster larvae attach themselves and grow.

Many of Goa’s oyster collectors live in clustered hamlets of brightly coloured houses along the banks of creeks and backwaters. While men and women are both involved in the collecting, it is generally the women that do the shucking (removal of the oyster meat from the shell), cleaning and discarding the shells just outside their homes, along the banks of these creeks. During the summer months, piles of oyster shells are a characteristic installation outside the homes of many of these creek fishers, exposed at low tide. The tides later disperse these empty shells back into the creek, where they become an extremely important substrate onto which free-swimming oyster larvae attach themselves, at which stage, they are called ‘spat’. Some of the large shells and oyster rock clusters are known as ‘mother shells’ (Calvam Hadde in Konkani, or Corpam for oyster shells). They are critically important as they provide a larger surface area onto which young oyster larvae can attach and grow. As a rule, Goa’s oyster fishers would shuck these mother shells while they were out collecting in their canoes, or as soon as they got back to shore, to return the mother shells to the environment. This helps sustain future production of oysters in the area.

However today, it is not just the people who live along the creek that harvest oysters. Being a tourist state, oysters and mussels are in very high demand, bringing collectors from other parts of Goa in large numbers, to these oyster-rich areas. A large part of the problem is that they take more than just oysters. These tidal flats and the shellfish they support are open access resources, which means anyone can harvest as much as they want — a common problem faced in coastal and marine spaces that leads to overexploitation. To make transport easy, these collectors gather entire rocks, complete with mother shells and all, which they then fill into empty cement bags, transporting them back to their respective villages, often in the hinterland with no access to a creek or backwater. These missing dead shells would have performed yet another important function. Built of calcium carbonate, the alkali slowly leeches into the water neutralising the acid levels in the estuary. This is extremely important as acids in the water can dissolve the shells of crustaceans and molluscs (snails, clams and oysters) exposing them to the elements and making them vulnerable to predators. Who would have imagined the removal of oyster shells could be linked to decline in oyster production world over? For the same reason, reintroducing oyster shells (shell planting) is a common method used to restore degraded oyster beds. However today, our oceans are becoming so acidic that even this practice is not enough to restore balance. Ocean Acidification is the result of increasing levels of CO2 in the atmosphere, primarily linked to the burning of fossil fuels, which then dissolves in seawater. This acidification threatens the lives of many of our seafood favourites including lobster, crab, shrimp, oysters, clam and others — basically everything that has a shell. We now need these shell resources in our oceans more than ever before.

Men duck dive for the large Brackish water oysters in the Nerul creek

A Sustainable Choice
Oysters collected and farmed the right way are a very sustainable seafood option. They are lower down the food chain and their populations can recover well, even after a heavy collection, if allowed sufficient time. They also make good candidates for aquaculture. They are filter feeders, which means they obtain their food by sucking in large quantities of water through their gills; algae and plankton suspended in the water get trapped in their gill mucous, and ultimately make their way into the digestive tract. Simply put, farmed oysters do not need to be fed, and can be a low-cost enterprise. In contrast to this, the species commonly farmed in India, such as shrimp and Asian sea bass, have very high feed requirements. To grow a kilogram of Asian sea bass you would require 6- 7 kilograms of fish feed. Fish for this feed comes from ecologically destructive trawl fisheries, and constitutes the low-value species in the catch called ‘trash fish’. My research into this subject has found that although ‘trash fish’ may not have high commercial value, it constitutes a vast diversity of species including juveniles of commercially important species that are an important source of protein for millions of poor coastal communities in India. Aquaculture is currently being celebrated as the solution to our future food requirements, and to the overfishing crises. However, you don’t need to be a scientist to know that farming fish such as sea bass, using current methods, is certainly not the smart way forward.

Whether it’s oysters, mussels or clams, it seems that Goa cannot keep pace with growing demands. Today, a large proportion of mussels and clams consumed in the state’s restaurants and beach shacks have actually been brought in from other states. 

Chicalim, and the Fight to Reclaim Goa’s Oyster Bay
The large expansive bays of Sancoale and Chicalim along the Zuari river are among Goa’s shellfish hotspots. It almost feels like the human relationship with this ecosystem has remained unchanged for centuries; stake-nets still necklace the mouths of these bays. In the summer, large numbers of people can be seen collecting clams and oysters here. It is also one of the few remaining habitats in Goa where you can find window-pane oysters, whose shells continue to adorn the windows of many Goan homes. Unfortunately, this year’s hot summer, coupled with low spring tides, left the extensive tidal flats and their oyster rocks exposed. People stuck at home during the lockdown, from several villages surrounding the bay, descended in hordes onto these flats, stripping them of oysters. Rather than leaving the mother shells behind, they carried away sack loads of oysters shells. This was much to the consternation of locals who feared for the future of the oysters, and the bay’s health in general.

Oyster-encrusted rocks and a lone mangrove exposed at low tide in Pallolem

However, it would be unfair to attribute the decline of the bay and the demise of oyster fisheries to over-harvesting alone. Unused iron ore barges are anchored at various parts along this river stretch. Exposed to the forces of nature, they lie in a state of decay, leaching pollutants into the estuary. The degradation of these bays will not only affect bivalve habitats, but also species that use these sheltered areas as feeding grounds and nurseries. Destruction of these important estuarine habitats can ultimately translate to the decline in quantity and quality of some of Goa’s favourite seafood. The brackish water oysters can live for several years, and both the live oysters and their shells are extremely important to the creek’s health. The high densities of molluscs found here perform a massively undervalued service to Goa, which is filtering the estuary of its pollutants and toxic algal blooms (which happens when there are high levels of domestic sewage in the water). These blooms deplete the oxygen in the waters, and can cause massive fish die-offs, threatening local fisheries.

The villagers of Chicalim and Sancoale have taken it upon themselves to save their bay. For the first time this May, several locals concerned about their bay’s future went about planting Calvam haddes. To stabilise these mother shells, they covered them with nets, and monitor them regularly. We still have a long way to go, but the current pandemic has opened our eyes to the need to strengthen local food systems. Much like the local shellfish food-chain, all local production of foods needs to be analysed in a similar manner to increase the resilience of supplies.

So what is my alternative to Goa’s oyster bhaaji? I reserve a batch of handpicked Nerul oysters, and use a straightforward, delicious Thai recipe I learnt from my uncle, Peter Estibeiro, who loves Thailand (and its oysters) as much as I do. First, make sure your oven grill is hot (or you can a pan, if you don’t have a grill). For sauce, chop up a few birds’ eye chillies, onions and coriander, to which you then add fish sauce and lime juice in equal parts. Bake or lightly pan-fry the oysters for under 5 minutes, to prevent them from turning chewy. Drizzle with sauce, and serve. Peter recommends having a batch crispy-fried burnt garlic on hand, to sprinkle on just before eating.

Aaron Savio Lobo is a marine conservation scientist, and a member of the IUCN SSC Marine Conservation Committee. You can follow his work here.

All photographs by Aaron Savio Lobo.



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