Annex VII
STATUS OF SANITATION AND MARKETING IN INDIA

P.S.B.R. James
K.S. Rao
M.E. Rajapandian
V. Chandrika

I. INTRODUCTION

Molluscs are known to be highly palatable and nutritious food. They constitute a valuable fishery resource in various sectors of coastal India. Apart from its food value, it is one of the main sources of lime. The exploitation of bivalves has been observed to be only as a subsistence occupation, but the growing demand for protein food and multiple uses of the mollusc shell in lime-based chemical industries have created tremendous awareness of the benefits of exploiting and developing molluscan resources. Cephalopods, bivalves and gastropods are the principal groups of molluscs exploited from coastal, estuarine and backwater environments. The total annual production of molluscs is 1.4 lakh tons which is 10% of total marine fish landing. The yearly landing of cephalopods, bivalves and gastropods are 43,000, 96, 300 and 1, 256 MT, respectively. The exploited cephalopods include cuttlefish (60%), squid (39%) and octopus (1%). Bivalves comprise clams (70%), cockles (9.5%), mussels (3.6%), oysters (1.0%) and window pane oysters (14.5%). The gastropod is chiefly represented by the sacred conch Zancus spp. whose meat is a highly prized food and whose shell is of great commercial value. The cephalopods are fished in areas where the conventional finfishes and shrimps occur so that the management and development problems relevant to both groups are similar. The bivalves and gastropods are mostly sedentary or semi-sedentary, inhabiting the coastal waters, estuaries and backwaters. Thus management and development problems related to these species are different from the cephalopods.

The bivalves are largely influenced by the environmental changes such as rainfall, amount of freshwater discharge of rivers, tidal amplitude, temperature, changes in salinity and pH, and occurrence of obnoxious blooms of phytoplankton. On top of these are the domestic, agricultural and industrial pollutants. At present, bivalves such as clams are processed and marketed without much consideration for the product's sanitary quality. Although aquaculture practices on cultivable molluscs have not been initiated on a commercial scale, experimental trials on the farming methods of a number of species have been carried out and suitable farming techniques evolved (Mahadevan et al., 1980; Kuriakose and Appukuttan, 1980; Narasimham, 1980; Rao, 1980). Further, successful production of seed of a number of bivalves through hatchery has been achieved (Nayer et al., 1984, Appukuttan et al., 1987; Narasimham et al., 1980). These developments, with proper understanding of the toxicological and bacteriological problems would help in the formulation of suitable sanitary control measures. A proper programme for the development of molluscan shellfish along the coast of India would significantly contribute to the rural economy.

II. TOXICOLOGICAL STUDIES ON THE MOLLUSCAN SHELLFISH

As the sea becomes the ultimate receptacle of the industrial waste waters, agricultural run-off, fall out of power stations, and spillage of fossil fuels due to increase navigational activities, the organisms found in estuaries, backwaters and coastal waters became highly exposed to the toxic substances such as heavy metals and pesticides. Bivalves, particularly, show insidious tendencies to accumulate certain heavy metals and pose great health hazards to those who consume them. Recently in India, considerable attention has been placed on monitoring of pollution in coastal water bodies; and bio-assay studies are undertaken of the flora and fauna to find out extent of heavy metal concentration.

A number of trace and heavy metals are present in very low concentration in marine environment but it is difficult to directly estimate these metals in the medium. Certain suitable sentinel organisms such as mussels, oysters, and clams from various parts of India have been examined to assess the heavy metal concentration in respect to seasonalities, species, sex and size variations as well as the degree of toxicities of various metal ions (Unnikrishnan, 1984). Unnikrishnan and Balakrishnan (1986) studied the seasonalities in accumulation of trace metals such as copper, cadmium, iron, manganese, zinc and mercury in the oyster, Crassostrea madrasensis in Cochin backwaters in the west coast. High metal leads were observed in oysters when the estuary maintained high salinities from October to April. In Vellar estuary along the east coast, the concentration of iron in C. madrasensis was found to be high during the post-monsoon months and it was observed that the concentrations of dissolved iron showed seaward decrease in the estuary (Santhilnathan et al., 1956. Pillai et al., (1986) estimated the heavy metal load in a number of bivalves from the coastal waters of south India. Samples of the clams, Vellorita cyprinoides, Meretrix costa, Crassostrea madrasensis, Perna viridis and P. indica were examined. They found significant variations in the concentration of metals like iron, zinc, copper, lead, cadmium, nickel and cobalt. Of the bivalves, clams showed high concentration levels of all metals especially iron and zinc. Zinc level is high in oysters. Mussels tended to accumulate more iron. Characteristically low concentration of lead was associated with very poor concentration level in the medium. Lakhsmanan and Nambisan (1986), Rajan et al., (1986), Santhi et al., (1986) found that the accumulation pattern of heavy metal ions differed among metals and in various parts of the body. The studies on the accumulation patterns of mercury, copper, zinc and lead in green mussel Perna viridis indicated that the bio-accumulation potential of lead is much higher than other metals. Jasmine et al., (1987) found that small oysters contained significantly higher mercury content than larger ones. The accumulation is higher in gills and viscera than in mantle and muscle tissues. From experiments it had been noted that the tissue level incorporation of metal depended on the concentration in the medium. Santhi et al., (1986), Rajandran et al., (1987), Jasmine et al., (1987) found a relationship between the total mercury content and length, breadth and weight of flesh of C. madrasensis. The bio-accumulation of mercury decreased with an increase in size and weight.

Bio-accumulation studies on pesticides in mussels in Calicut region (Radhakrishnan et al., 1986) indicated the presence of 11 chlorine-based pesticides in the medium all of which were present in significant levels of concentration in mussels.

Effect of oil on physiological activities have been studied by Sophia and Balasubramanian (1986); when the oil concentration was at 50% of water soluble fractions, a significant depression was noticed.

Nambisan and Lakhsmanan (1986) assessed the relative toxicities of heavy metals in mussels. They estimated the mortality of P. viridis by exposing them to different concentrations of copper, mercury, zinc and lead for varying durations. They observed that of the four metals tested, copper and mercury were extremely toxic to mussel. In 0.50 ppm of copper, 50% died on the second day and all in the third day. Lead had no lethal effect even at a concentration of 10 ppm for ten days and longer. It had been viewed that the non-toxic effect of lead at such high concentration might be due to the presence of calcium ions in the medium. They found that toxicity of zinc and lead salts to mollusc was generally reduced with the presence of calcium salts. Nambudiri (1986) investigated the inhibiting effect of the heavy metals mercury, zinc, lead, and copper on enzymes. The mercury ions showed the greatest inhibiting effect on enzymes. Nambisan and Lakshmanan (op. cit.) evaluated the electronegativity data and pH values of the metal sulphide and ionic radii of the four metal ions of copper, mercury, zinc and lead. Investigations on the combined toxicity of a mixture of heavy metals were made by Menon et al. (1987). They observed that even at low concentrations (sub-lethal level) some metals in certain combination would negatively affect the physiological activities of certain bivalves. They also observed that in some cases certain combination of metals even at high concentrations did not cause any ill effect on the organisms.

III. INVESTIGATIONS ON DE-TOXIFICATION

The depuration of accumulated metals by relaying the bivalves in metal-free medium has been studied by Lakshmanan and Nambisan (1986). They observed that 23.3% of the accumulated mercury was lost in P. viridis during 20 days and 63% of the total copper was eliminated in 24 days. They also found that clearance of zinc at the end of 20 days was 40% and loss of lead in 20 days was 40% Lakshmanan (1987) conducted experimental studies on the depuration of metal-contaminated clams and oysters. After 48 hours of depuration, the concentrations of copper and zinc in the tissue of clams declined by 46% and 64%, respectively. In oysters, the loss of copper and zinc was 9% and 16%, respectively in 48 hours. By keeping them in filtered seawater medium with FS-EDTA at 100 mg/1 (1 ppm) the loss of copper and zinc was 37% and 46%, respectively.

IV. STUDIES ON SHELLFISH BIO-TOXINS

The bivalves, particularly mussels, oysters and clams, are the trans-vectors of marine bio-toxins or paralytic shellfish toxins. Dinoflagellates belonging to the genera Gonyaulax in temperate waters and Pyrodinum in semi-tropical and tropical regions are the most common sources of PSP (Ray and Rao, 1984). Of the three groups of bivalves, the greatest number of human poisoning had been traced to mussels. Outbreaks of paralytic shellfish poisoning occurred in India recently. The first record of outbreak was on the east coast in 1981 (Silas, 1982) and the second on the west coast in 1983 (Kana Sagar, 1984). In August 1981 a case of shellfish poisoning was reported from Vayalar Village in Tamil Nadu. Three children died and 82 others had neuro-toxic symptoms. Investigations by the National Institute of Nutrition, Hyderabad, showed that the clam Meretrix costa eaten by those afflicted was contaminated with toxin secreted by the dinoflagellates. In 1983 PSP was reported in M. costa and oysters from Kumbla estuary. The clams and oysters showed PSP levels of 18,793 mu/100 gm and 6,680 mu/100 gm, respectively. Despite the high initial toxic levels, the clams lost toxicity more rapidly than the oysters. The clams were free of detectable PSP after about 5 weeks while oysters retained small amounts of toxin for 7 weeks after initial evaluation.

In 1984, the Central Marine Fisheries Research Institute (CMFRI) conducted the Workshop on Marine Toxins in Bivalve Molluscs and general considerations of shellfish sanitation. The workshop was organized to evaluate the source and nature of bio-toxins, symptoms and treatment of shellfish poisoning, trans-vectors of shellfish poisons, techniques for monitoring bio-toxins, and prevention and control of shellfish poisoning (Ray and Rao, 1984).

V. BACTERIOLOGICAL INVESTIGATIONS

In many countries, bacterial infection constitutes the largest incidence of fish- and shellfish-borne diseases. In India, intensive investigations on the bacterial constitution of shellfish have been in vogue since the mid-fifties. Velankar (1955) found the proximate bacterial count of seawater was 200– 300 MPNS/ml and the coliform bacteria count 50–100/100 ml. The bacterial load in the surface water samples progressively decreased as the depth increased. The count increased with the increase in the amount of suspended particles. Venkataraman and Sreenivasan (1955) investigated the pollution at Kerapuzha estuary near Calicut, Kerala and found that P. viridis in shallow coastal waters were continually polluted and contained E. coli type I throughout the year. Surendran et al., (1986) observed very high levels of total bacteria as well as fecal coliforms in the flesh of mussels from the Kerapuzha estuary. They found that mussel harbour bacterial loads 10 to 100 times higher than that of the environment. Bacterial pollution peaked immediately at the onset of the southwest monsoon. Paracoli, Protono and E. coli which cause gastroenteritis were present. Jones and Alagarswami (1973) considered that mussels were poisonous or unwholesome during monsoon. Pillai (1980) made a quantitative estimation of bacterial load on the brown mussel P. indica from natural mussel beds and mussels cultured from rafts. The bacterial load observed in cultured and natural populations were 10⁶ and 10⁵ respectively. Pillai and Selvan (1987) estimated the total bacterial count on cultured (rack and tray) and natural oysters (C. madrasensis at Tuticorin, Gulf of Mannar as 10³ and 10⁴ organisms per ml of oyster fluid. Fecal coliforms were found to be at very low level and within permissible limit. The pathogenic bacteria such as Salmonella, Streptococci, and Staphylococci, were absent.

Chandrika et al. (1986) isolated certain fecal coliform antibiotic resistant bacteria from the clam M. costa. Of the 26 E. coli isolates 8 were found to be multi-drug resistant. This indicated that the possibility of widespread use of antibiotic in animals, animal feed and human being; their influence on estuarine environment could have provided the resistance factor of bacteria.

Sreekumari and Lakhsmanperumal (1986) conducted experiments on the effect of organo-phosphorous pesticide on some heterotrophic bacteria associated with the black clam Villorita cyprinoides. They observed that after treatment with an organo-phosphorous, Ekalux Ec 25 at sublethal concentration, the heterotrophic bacteria increased in population. Further, there was an increase in the percentage of amylase- and urease-producing bacteria. The hydrolytic enzymes of bacteria were also high in certain regions of the clam. The pesticide in sublethal levels thus promotes development of enzyme producing bacteria which in turn enriches the enzyme pool of the microcosm. This factor evidently influences the substrate recycling in terms of energy flow in the estuarine food-web.

The occurrence and distribution of heavy metal resistant bacteria in waters and in association with black clam of Cochin backwaters have been studied (Sreekumari and Lakhsmanperumal, 1987). Heterotrophic bacteria and black clam were identified and isolated. Metal sensitivity of selected bacterial isolates was tested with salts of mercury, zinc, copper, cadmium and lead. All the isolates tested were found resistant to zinc and lead. Resistance to mercury, copper and cadmium varied among isolates. Isolates from water exhibited higher resistance to mercury, cadmium and copper than those from animal samples. It has been indicated that the sensitivity of certain heterotrophic bacteria to heavy metals was retarded due to the constant and continuous influence of heavy metal ions on these bacteria.

VI. INVESTIGATION ON SHELLFISH SANITARY CONTROL

In India, molluscs are consumed as they are collected after cooking. The bivalves are notorious for their propensity to accumulate pathogenic bacteria, heavy metals and other pollutants as well as bio-toxic substances such as PSP. Although there was no awareness of these problems in the past, there is now a great attention in evolving suitable and workable techniques to purify the bivalves before they are marketed. Research institutes and University centres have taken up programmes to assess the quality of coastal waters and delineate areas which exhibit pollution, and to propose measures to prevent and control pollution.

VII. DEPURATION OF SHELLFISH

Balachandran and Nair (1975) and Nayar et al. (1983) designed mussel and oyster cleaning tanks. The depuration plant in operation in Tuticorin can satisfactorily purify oysters at the rate of 14,400 pcs (about 1,300 kg) in 24 hours. The harvested oysters are cleaned of silt and other debris by a strong jet of seawater. The oysters are placed in trays one or two layers deep and the trays placed in concrete cleaning tanks or wooden grids. A slow and steady flow of water is maintained in the tank for 12 hours. At the end of this period, the drain valve is released, the oysters are flushed with a strong jet of water and once again this operation is repeated for another 12 hours. After this, the flushing is again carried out and the oysters re-layed in chlorinated seawater for 1 hour and flushed one more time with a strong jet of seawater. Rajapandian et al. (1987) studied the effect of hydrological factors on the depuration process and evaluated the optimum level of the hydrological factors such as temperature, dissolved oxygen, salinity and turbidity to control the purification process. They observed the total plate count of the bacteria as 10³ and 10² before and after purification, respectively. Faecal coliform count in oysters were found to be 7 to 37 per gm. Surendran and Balachandran (1984, 1987), Pillai and Selvan (1987) conducted experiments on depuration of oysters, clams and mussels. After relaying the bivalves for 24-48 hrs and treatment of the bivalves in 5 ppm chlorinated water, there was a greater reduction in bacterial count.

VIII. PRODUCT DEVELOPMENT AND QUALITY CONTROL

Due to dining out habits and affluence in many countries, seafood products have become one of the essential constituents in the daily food itinerary. Although molluscs are available throughout the year, they are preferred during certain periods. It is often a problem of balancing quality and quantity, for when shellfish are plentiful they are usually of good quality (i.e. meat condition is good). This condition coincides with summer when people normally prefer other varieties of seafood to molluscs. In cold weather, people prefer bivalves when the meat quality is lower and availability is scarce. The oysters, clams and mussels along Indian coastal waters also exhibit certain seasonalities meat condition. Rajapandian and Rajan (1983) observed bi-annual peaks in the condition of oysters and mussel meat. Harvesting of these bivalves would be economical during such periods.

The total annual world production of processed oysters, clams and mussels comprises frozen products (23%), dried products (4%) and canned products (73%). This clearly indicates the canned products have a high market potential. Although canning requires a high capital investment and higher processing cost, a stable finished product is obtained which can be marketed at any period of the year.

Balachandran and Nair (1975) developed a process for canning clams and mussels in hot refined ground nut oil. Samuel (1982, 1987) reported the processing of clam, grading and freezing for export and described the various canned products of oysters, clams and mussels. Of these, the smoked canned oysters to have the best market potentiality in India. Canned oyster products, i. e. oyster in brine and smoked oyster in oil, were successfully developed by the Integrated Fisheries Project at Cochin. These products were well accepted by consumers and particularly the smoked oysters in oil. The shucked oyster meat is simmered in 5% salt solution for 5 minutes and arranged on wire mesh trays inside the smoking chamber. Smoking is effected initially at 40° °C for 30 minutes and then at 70° for 80 to 90 minutes. Smoked oysters are packed in quarter dingly cans with a net weight of 80 gm per can. Hot double refined ground nut oil is poured into the can and seaming done immediately. The seamed cans are sterilized at 115°C for 25 minutes under pressure (2 kg/cm²) inside the retort. Sample cans drawn at random are incubated for 2 weeks and tested for bacteriological and organoleptic analysis before being released for sale. Other products such as smoked mussels (Muraleedharan et al., 1979), pickled mussels (Balachandran and Prabhu, 1980) have been developed.

IX. QUALITY CRITERIA AND CODE OF PRACTICES FOR HANDLING AND PROCESSING

Since all bivalves invariably contain mud and high levels of bacterial load, depuration of bivalves is recommended as a statutory formality before further processing of the materials (Gopakumar, 1987). Cleaned natural water, filtered brackish water or seawater has to be used to purify bivalves. Depuration for a period of 18–24 hrs in live condition results in 90% reduction of the bacterial population. A subsequent washing of the meat in 5 ppm chlorinated water to a large extent renders the material safe for human consumption. All molluscan processed products are recommended to contain a certificate specifying the levels of metallic residues as per proposed standards.

X. MARKETING OF MOLLUSCAN PRODUCTS

At present, clams, mussels and oysters fished from different coastal villages and towns along the east and west coasts are marketed in the same places and nearby areas. In the west coast, mussels are mostly consumed locally but oysters are eaten in limited quantity mainly because of poor accessibility. The widely exploited resources are the clams, M. costa, M. meretrix, Katalysia opima, Paphia malabarica, and Villorita spp. Table 1 shows molluscan products exported By India during the 1981–85 period.

Mussels. Annual production of mussel is approximately 3,500 MT. The bulk of production is consumed locally and a small quantity is exported as canned product. The price of mussel varies from Rs. 10–20 per 100 pieces, shell on.

Table 1. Quantity and value of exported molluscan products. Q: Quantity in MT; V: Value in thousand Rs. (From: MPEDA).

Clam. The total clam production of India in 1984 was 78,900 MT. of this some, 1,090 MT of frozen meat or 15.3% of total product was exported. Price of clam meat varies with species and location from where they are fished. Katalysia opima, the baby clam fetches a local price of Rs 1.25 per kg shell-on, and Rs 7.50–12.00 per kg meat. The total value realized through exports of frozen clam was around Rs. 15.2 million in 1984. The major buyer of Indian baby clam is Japan; other importing countries are the U.A.E., U.S.A. and West Germany. Minor quantities of canned clams and clam pickles have been exported. Apart from the baby clam, the yellow foot Paphia malabarica has great market demand in Japan. Attempts are being made to organize the export of this clam.

Oysters. The Marine Products Export Development Authority of India have received a number of enquiries from foreign buyers for frozen oyster meat produced from culture. Efforts have been made to organize oyster culture on a commercial scale. Oyster shells from oyster fished from the wild are exported in powder form. The export of this product has been growing. During 1984, 654 metric tons of oyster shell powder valued at Rs. 4.61 lakhs was exported.

In India, marketing of canned oysters has met with great success. The Integrated Fisheries Project at Cochin has been marketing these products by selling directly to consumers and through the State Fisheries Development Corporation, Cooperative Department Stores, super bazaars, and other outlets, on preferential basis, in order to make the products available at reasonable prices. Canned oyster products were released for sale in 1984 onwards. The Integrated Fisheries Project holds that oyster is liked not only by the high income but also by the middle income group. The whole of northeast India responds seasonally well to this product, although it is a little higher in price. At present, the northeastern states viz. Mizoram, Nagaland, Assam, etc., accept any quantity of canned products; 50 tons of oyster meat per annum is the minimum requirement at present. When this quantity is put into the market with accompanying publicity, it could very well stimulate demand to the level of 100 tons per year.

Gastropods. The sacred conch Zancus pyrum is the major species exploited in commercial proportion in India. The production of full-sized conch was about 1,429,940 during 1982–83. Average meat yield per conch is 60 gm. The local price is from Rs. 10 to 12 per kg (wet weight). The price offered by importers abroad is 2–3 U.S. dollars per kg of frozen meat. On average, during the conch fishery season, some 85,800 kg of conch meat could be shucked which could earn foreign exchange equivalent to Rs. 25 to 35 lakhs. The cost of the shell of conch varies depending on the size and condition. On an average it costs Rs. 15 apiece.

Other Seashells. The average export of ornamental shells during 1981–85 was 333 MT at Rs. 15.39 lakhs. The ornamental molluscs have limited distribution and meat of the species would take many years to reach commercial size. Gastropods grows slower than bivalves. Further, several species of gastropods are important resource material for bio-active substances. However, the exploitation of gastropods does not parallel their abundance. Under these circumstances, it may not be prudent to continue to export the ornamental gastropods until the resources are investigated in detail and their initial uses ascertained (Alagarswami and Moiyappan, 1988).

XI. DISCUSSION

The proper management of shellfish sanitation largely depends on the development of a systematic and continuous programme of monitoring the grow-out sites and formulation of suitable and economically viable systems to control pollution in their habitats. In India, recently, a growing awareness of the importance of protecting the coastal marine environment from the deleterious effect of pollution on bivalves and other organisms, has set in. Central and State level agencies have been established to look into the problems of pollution in land, atmosphere and water. A National Mussel Watch programme was organized in 1986 and the status and effects of pollution along the southwest and southeast coasts of India have been reported to some extent.

Marine biological research organizations and oceanographic research centres of the country have made a headway in accomplishing preliminary investigations on the nature, pattern and seasonalities of pollutants that influence the coastal waters and the resultant effects on the biotope. Bio-assays on certain selected sentinel organisms such as mussels, clams and oysters were undertaken from various parts of coastal India. These studies have indicated seasonal variations, species and size variations of the bio-concentration of various metal ions. The organisms showed definite variations in the tissue level incorporation of metal ions in different parts of the body. Accumulation pattern of the various metal ions have ben studied and certain metals like iron, zinc and lead exhibited very high bio-accumulation tendencies. Experiments on the relative toxicity of different metals and the combined toxicity of mixed metal salts have also been carried out. Although these studies form a baseline for investigation of prevailing and possible levels of metal pollution in coastal waters, a realistic approach on the evaluation of the synergistic effects of different metal salts present in the estuarine environment is needed.

Based on these studies, anti-pollution measures and formulation of pre-treatment procedures of domestic, agricultural and industrial effluents have to be evolved soon so that pollution could be controlled effectively at the initial level instead of attempting to repair the deformation of the ecosystem much later.

De-toxification research on metal-contaminated shellfish is at the initial stage. Attention must be directed to understand more about the inherent physiological intricacies of the bivalves and to utilize their own de-toxification mechanisms to remove metal ion concentrations from their systems.

Depuration aims to ensure that pathogenic organisms are either absent or present only in quantity that would have no debilitating effect on humans. Depuration of bivalves and rendering them free of bacterial contamination has been studied to some extent. However, more effective and inexpensive techniques should be evolved and standardized for wide and common use along the coastal areas.

In order to improve and standardize the quality of molluscan products, depuration procedures have to be coded and declared mandatory. The metallic residues in the products have to be assessed and standards prescribed.

Before attempting to formulate any legislation on the control of pollution and enforcing sanitary regulations, it is advisable to create public awareness on the subject so that control measures and enforcement of regulations would have the desired effect. Coordination between scientists and law makers would greatly help to achieve this goal.

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