| Abstract |
Elevated levels of toxic metals like Cd, Zn, Cu, etc., have been observed in various molluscan shellfish which caused concern world wide. Cephalopods, mussels, clams and oysters constitute the major molluscan fishery of India. While other molluscan shellfish are of local importance. Cephalopods, particularly squid and cuttlefish, constitute around 20% of the total export of Indian marine products. Considering its importance in global trade, the safety of the product is of great concern. Higher levels of some of these metals are implicated in health problems among the consumers. Disease of the dancing cat, iwi- itai disease and black foot disease observed in Bangladesh recently are examples. The levels of Cd, Hg, Pb, As, Cu, Zn, Mn, etc., monitored in cephalopods from different geographic locations indicated higher levels of Cd (> 2 ppm) and lower level of Hg (<0.1 ppm ). Clams, mussels and oysters from Cochin area had comparatively higher levels of some of the metals (e.g. Zn ). Geographic variations in metal levels were observed in cephalopods. Higher levels of Cd, Zn, Cu have been observed in the whole soft parts of squids and cuttlefish and also in the liver. Cadmium content exceeded permissible limit in around 10% of cephalopods, when whole soft parts were analyzed. Feeding habits of cephalopods seemed to play a major role in the accumulation of heavy metals. High levels of metals in the various food fishes separated from the mantle cavity of cephalopods and in the fishes caught in the same trawl net along with cephalopods confirm this view. Metal levels in mussels, clams and oysters were generally found to be high, in agreement with the observations made elsewhere. Higher level of Cu in cephalopod liver and Zn in oysters may be natural since they are required by the animal for the production of haemocyanin or carboxylase enzyme. Environmental pollutants may affect safety of farmed oysters and mussels. The values are compared with the results reported from other parts of the world. Keeping a clean environment and regular monitoring of hazards in water and some of the molluscan shellfish would indicate the quality status of the environment. Following a GMP linked HACCP based approach in the primary and processing sectors would guarantee safe seafood. Depuration has been made mandatory in shellfish processing regions by developed countries. |
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