Authorities neglecting poisonous shellfish

Sandesh Prabhudesai
16 January 2002  

Poisonous shellfish is causing concern in Goa, a tiny coastal state on Indian West Coast.

Following fish kills witnessed three months ago off Canacona, the southernmost taluka (province) of the tourist state, marine scientists have pulled up their sleeves soon but not the state authorities.

Fortunately, there are no casualties reported till date, but the ‘risky’ shellfish is still being fished out from the ocean and openly sold in the market. Goa’s 80 per cent population eats all kind of fish, including the shellfish.

In fact shellfish like mussels, oysters and clams are the delicacies here for the tourists, who start flocking down to Goa from all parts of the world from October onwards. But this delicacy, which has become little risky, is being freely served in the restaurants all over.

The National Institute of Oceanography, a sole institute in India researching on marine science, has immediately moved into action to find out that the toxin produced by the toxic alga bloom is accumulated by the shellfish, rendering it unsafe for human consumption.

"The alga bloom noticed off Goa was caused by the toxic alga Cochlodinium polykrikoides. To the best of our knowledge, this is the first report of this alga along the coast of India", states Dr S R Bhat, the NIO scientist.

During their coastal research, the NIO found that large parts of the inner and mid-shelf between Goa and Mangalore (in Karnataka state) were covered by cold waters that had been brought up from the deeper, offshore layers and had lost all their dissolved oxygen.

While this oxygen deficiency could have caused the fish kills, the scientists have also found a toxic alga boom near Goa. "We are further investigating whether the two events were related to each other", states Dr Bhat.

Experiments have however confirmed that the alga was toxic to test organisms such as copepods and it is the first reported occurrence of this organism from the Goan waters. It is known to cause paralytic shellfish poisoning (PSP) and diarrhetic shellfish poisoning (DSP).

"Our fears have come true. We have polluted the coast and the ocean is taking a sweet revenge by producing Harmful Alga Blooms which are ingested by shellfish", observes Dr Nandkumar Kamat, a microbiologist from Goa University.

The fisheries department should immediately ban shellfish while maintaining vigilance at jetties and markets, besides public awareness, urges Dr Kamat. But the state has done very little till date, except releasing one small press statement regarding public vigil.

"It’s true, we have not done much in this regard. I will immediately take stock of the situation and take all the necessary steps", said fisheries minister Prakash Velip, who was found to have been unaware of the intensity of the whole issue.

DSP and PSP are among the five most significant public health problems caused by harmful algae, which also occur in various coastal waters of the US and the world. Translocation of cysts of dinoflagellates through ballast water used in ships is considered to be one of the vectors of it.

Looking at the symptoms of diarrhetic shellfish poisoning, Dr Oscar Rebello of Goa Medical College admits that he has witnessed unusual spurt of diarrhoea since last three to four weeks, which is normally found during monsoons in Goa. Though the GMC has considered it be a kind of virus, he does not rule out the possibility of shellfish consumption as cause of it.

Though DSP is non-fatal which causes at the most of nausea, vomiting, abdominal cramps and chills etc, the paralytic shellfish poisoning is a life-threatening syndrome, having neurological symptoms resulting even into respiratory arrest within 24 hours. Dr Rebello admits that no such case has been witnessed at the GMC till date.

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