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Indian J. Fish., 49(1) : 85-91, Jan.-Mar., 2002

A review of the black clam (Villorita cyprinoides) fishery of the Lake

P. LAXMILATHA AND K.K. APPUKUTTAN Central Marine Fisheries research Institute, Cochin - 682 014, .

ABSTRACT The black clam, Villorita cyprinoides, is an important fishery of the Vembanad Lake and contributes to over 70% of the total fish production from the Lake. Factors which affect the sustainability of this fishery are indiscriminate exploi- tation of small-sized clams, closure of the Thaneermukham Barrage, frequent dredging, pollution due to retting, effluents from shrimp processing plants / factories and swarming of weeds. The present status and management options for this important fishery are discussed.

Introduction which supports the lime and cement in- dustry in and Tamil Nadu, is ana- The Vembanad Lake, is one of the major estuaries in India. It is situated lysed. The need for management and con- between latitudes 9°28’ and 10°10’ N and servation measures to develop and sus- longitudes 76°13’ and 76°31’E in south- tain this valuable resource is highlighted. ern Kerala. It has a length of about 90 Materials and methods km and extends from Alleppey to Azhicode with water spread area of 300 Observations on the fishing activities sq.km. The Vembanad Lake supports a during peak fishing season were made. rich fishery of clams of which Villorita The detailed information on the black cyprinoides, the black clam, contributes clam production over the past decade, the to over 70% and the monthly average fishery trend, post harvest processing, production was 2619 t during 2000. utilization, socio-economic factors, the Rasalam and Sebastian (1976) reviewed problems and factors affecting the black the lime shell fisheries of Vembanad Lake clam production and management issues highlighting the various management were collected from the seven black clam issues. Achary (1988) studied the char- lime shell cooperative societies operating acteristics of the clam resources in Vembanad Lake. The present status of along the Vembanad Lake. Enquiries this important fishery of the Lake is re- were made with the local people in the viewed in this paper. The effect of fish- major black clam fishing areas for fur- ing pressure on this important resource, ther details.

85 P. Laxmilatha and K.K. Appukuttan 86

TABLE 1. Details of black clam fishery in the Vembanad Lake Name of Black Fishing No.of No. of No.of Average Average Clam Lime Shell Villages area registered active canoes fishing catch/canoe Cooperative (Ha) clam fishers days/ /day (Tins) Society fishers Month 1 Tin=20 kg Kundanoor 200 710 300 155 12 4 Panangad Thycattussery Thuravoor south 350 200 19 8 Pallipuram 300 1000 Kokothamangalam Thaneermukham 350 1000 600 300 15 5 Thaneermukham 400 900 378 300 18 6 Kumarakom Thaneermukham 500 236 125 100 15 7 Kumarakom Vaikom 94.5 500 300 300 15 25 Pallipurathussery Chembu Chembu 10 187 95 90 15 3 Kattikunnu

Results and discussion Fishing areas Lime shell Co operative societies White Lime shell Co operative societies Mining grounds The black clam fishing in Vembanad Natural Clam beds Lake extends from Komalapuram in the south to Panangad in North. Fishing for the black clam is done essentially for the shell rather than the meat. The fishing rights and licenses for fishing in the lake are issued by the State Department of Mining and Geology which has, to some extent, helped to organize the lime shell fishing activities. The license is issued to seven black clam lime shell cooperative societies situated along the various fish- ing areas of the Vembanad Lake which in turn issue license for fishing to their members. Selected areas (villages) are demarcated for each society (Table 1, Fig. 1). The total fishing area leased out to societies extends to about 1855 ha. Fishing methods Fishing for live clams in Vembanad Fig.1. Vembanad Lake: Black clam fishing Lake is done by 1) hand picking by areas and Cooperative societies women and children in shallow areas,

86 Black clam fishery 87

where the depth is less than half a metre, during low tides. About 1-2 baskets are collected by this method. 31430.54 Production (t) 2) Fishing is practiced by women in slightly deeper areas of less than 1.5

10.95 2619.21 m without diving- the women feel and detect the clam bed by their feet and remove the clay over the buried clams by their feet to accumulate the clams to a particular spot and guide the col- lected clams to their bamboo or alu- minium baskets (“unda”). Nearly 3-4 baskets (6-8 kg) per women are col- lected by this process. 3) Fishing is also done from a canoe, mostly by men, by using a hand operated dredge locally known as “Kolli” or “Varandi”.

during 2000 The black clam fishery Clam fishing is carried out for 15- 16 days a month involving roughly 2148 active fishers. The average catch per canoe per day is highest (25 kg) from the Vaikom - Pallipurathussery area registered with Kuthiathode so- Villorita cyprinoides ciety (Table 1). The site of clam fishing varies every year, due to changes in the spat 29.8 14 3.51 3.51 1.75 1.75 12.80 3100.95

Length frequency in percentage fall pattern owing to various environ- mental reasons. The fishers have Fishery details of

11.7 11.7 6.67 3.33therefore, 10 1.67 adopted the practice of 9.33 1946.83

2. transplantation / semiculture wherein they collect the spat from ABLE 19.611.7 23.2 30 30.4 12.5 20 3.57 10 1.79 6.67 10 1.67 1.67 1.67 3.33 14.07 1654.61 10.00 3429.52

T areas where dense settlement has occurred and transplant them to places (near their homes/homesteads) where no spat fall has occurred. This is more prevalent in certain areas 8.62 191.82 25.9 1.82 22.4 14.6 3.45 29.1 12.1 14.6 5.17 14.6 3.45 14.6 1.82 3.64 1.82 1.82 9.19 13.23 1786.92 1104.62 1.67 10 6.67 15 33.3 18.3 10 1.67 1.67 1.67 10.00 2710.70 such as Nettoor, Kumblangi, Cheppanam and . This fa- 1.75 7.02cilitates 29.8 12.3 the 22.8 harvesting/ 12.3 7.02 3.51 picking 3.51 at a 11.65 2233.95 more appropriate time. This practice

10 12 14 16 18 20 22 24 26is also 28 carried 30 32 out 34to prevent 36 38 the 42 de- Meat% struction of the baby clams due to the effluents released from shrimp peel- (mm) MayJuly 1.67 13.3 15 8.47 15 18.6 10 17 16.7 8.47 16.7 10.2 6.67 10.2 3.33 20.3 1.69 1.67 50.8 8.86 3290.88 11.20 2857.96 June 5.08 8.47 30.5 18.6 8.47 3.39 8.47 8.47 6.78 1.69 11.86 3407.46 April 3.33 Total ing sheds and areas where fishing is March 8.93 August 3.51 8.77 19.3 14 October 42 3.33 10 Average January 3.92 1.96 5.88 5.88 15.7 11.8 19.6 17.7 7.84 3.92 1.96 1.96 1.96 9.22 3906.14 February December November September Month\length hampered by clogging of weeds. Fish-

87 P. Laxmilatha and K.K. Appukuttan 88 ery for the black clam, extends from Oc- Lime shell cooperative societies tober to March with the peak during De- The black clam exploitation from the cember to March (Table 2). Vembanad Lake is more or less organ- Clams of 20-24 mm length support ized by seven black clam lime shell coop- the fishery with the dominance of 20-22 erative societies. The cooperative socie- mm group during April. The wet meat ties buy the shell from their members at weight percentage which varied from 9.2 the rate of Rs. 600-700 per ton. They are to 14.07% was maximum during April. also required to pay a royalty of about Males were dominant in the population Rs. 20-30/ton to the Government. The throughout the year with sex ratio of shell is sold to agents from Kerala and 80:20. V. cyprinoides is a continuous Tamil Nadu at an average rate of Rs. 800- breeder, with peaks in February-April 1000/ton. The shell in turn is sold to lo- and November-December. Seed clams cal limekilns, cement, pharmaceutical occurred from October - November on- and carbide industries. wards. Each society has registered clam Production fishers of which only 50% may be regu- lar fishers. The level of black clam exploi- The total annual production of Villorita cyprinoides from Vembanad Lake, over the last sixteen years is indi- cated in Fig. 2. The monthly average pro-

Fig. 3. Villorita cyprinoides, Society wise pro- duction, during 1985-2000

tation from Vembanad Lake by the soci- Fig. 2. Villorita cyprinoides, Total production eties from 1985 to 2000 is depicted in Fig. in Vembanad Lake, during 1985-2000 3. These societies, besides organising the sale of lime shell for the clam pickers, also duction has increased from 971 t in 1985 implement several welfare schemes. to 3106 t in 1999. However, a significant Since the societies are governed by the increase during the period 1990 - 1994 State Department of Mining and Geol- followed by a drastic decline in the total ogy, the welfare schemes of the Govern- production during 1995 - 1998 indicates ment open to other coastal fishing probably, a cyclic trend in the clam seed populations are not available to these settlement pattern. In 1999, again a sig- clam fishers. However, the cooperative nificant increase in the total production societies have made relentless efforts to was noticed, followed by 20% decrease in extend some of the rural development 2000.

88 Black clam fishery 89 schemes to these clam fishers. Educa- found as sub-soil deposits over large ar- tional loans, disaster aids, emergency eas, upto several feet below the surface loans etc. are granted to them. of the soil. The sub-fossil deposits are The cooperative societies are also formed as a result of smothering of large involved in providing supportive meas- live clams by the mud and silt carried into ures to the clam fishers to increase the the lake by the floodwaters during mon- clam production. For instance, the soons. The sub-fossil lime shell are uti- Komalapuram society organises the fish- lized as raw material by various indus- ing activity of their members in a rather tries such as lime kilns, cement, carbide, unique manner. There has been no seed medicine, pharmaceutical, fertilizer, pes- settlement in the south region ex- ticide etc. The Vembanad Lake is rich in tending from Muhamma to sub-fossil lime shell deposits accumulated Komalapuram. This has been due to clo- through centuries of accretion. sure of the Thaneermukham barrage and There are five white lime shell coop- dredging. Added to this, the heavy infes- erative societies engaged in lime shell tation of the African weed Salvinia exploitation and fishery. Large scale com- auriculata and the water hyacinth, mercial dredging is also in vogue in the Eichhornia crassipes also affected the lake. It is estimated that an average of fishing activities, especially during the 40,290 tonnes of fossil shells are dredged monsoon and post-monsoon months. The annually from 586 hectares of water area. society has, two hired mechanized boats The average annual consumption of the (hiring charge Rs. 650/boat) and the clam lime shell for cement production is 40,219 fishers are transported along with their tonnes. The meat extracted by heat canoes and fishing gears to the more po- shucking, is used for local consumption tential clam beds of the Kumarakom and as a feed in shrimp farm. waters ( District), 12 km from Factors affecting sustainability south Aryad. The canoes of the clam fish- ers are tugged to the fishing area in the Indiscriminate exploitation of under- early hours (at about 0500 Hrs) and al- sized clams due to the high demand, re- lowed to fish up to noon and are tugged sulted in depletion of the stock. The use back to south Aryad. The fishers pay a of hand-dredge with narrowly spaced, nominal fee of Rs. 20/- towards tugging large rakes and small mesh (5-20 mm) charges and Rs. 15/- for hiring of the ca- size of the scoop net, cause the destruc- noe. The fishers are able to fish about 10- tion of the clam beds through harvest of 16 tins /day/canoe as against 4-5 tins/day under-sized clams. earlier. This is almost double the catch The closure of Thaneermukham Bar- compared to the earlier years, when fish- rage from January to May every year ing was done in the nearby areas within changed the salinity profile and resulted Aryad. Also, this reduces the effort ex- in drastic ecological changes in the lake, pended for fishing in the weed-infested particularly south of the barrage, affect- areas. ing the distribution and survival of the Sub-fossil exploitation living resources, especially depletion of The lime shell, is classified into black the black clam in several parts (Pillai, shell and white shell. The black shell are 1991). Areas, which were highly produc- by-products from the black clam after ex- tive about fifteen years ago, have become traction of the meat while, white shell are barren now and caused severe dislocation

89 P. Laxmilatha and K.K. Appukuttan 90 of thousands of clam fishers. Frequent clam production levels. dredging (mechanized fishing) activities, Fishery management has resulted in suspension of silt caus- ing smothering of clam beds and affect- Enforcement of conservation and ing settlement of seed in these areas. management measures such as closed seasons, mesh size regulation for the The fact that the license for clam hand dredge to prevent indiscriminate fishing in Vembanad Lake, issued by the exploitation of under-sized clams are pro- Mining and Geology Department has posed together with promotion of a sys- severly restricted the development of the tem of relaying and culture of clams in clam fishing community. Since they do Vembanad Lake. This system is already not come under the purview of the Fish- in vogue in some parts of the Vembanad eries Department, they are denied the Lake viz; Nettoor, Kumblangi, rights and benefits available to other Cheppanam. These practices must be coastal fishing communities. Fishing is promoted on a more scientific basis adopt- carried out by licensed as well as non- ing proper site selection, stocking densi- licensed fishers, leading to social ten- ties, protective measures etc. For the sions. maintenance and conservation of Dumping of clams, (especially seed broodstock clam sanctuaries/parks may clams which do not have high meat con- be established at suitable areas. tent), for the decomposition of meat and Issues for intervention subsequent retrival of shell for the lime industry leads to pollution as well as Sub-fossil shell extraction may be re- waste of enormous quantity of clam meat. stricted to deeper areas of the Lake and Also the environmental/health hazard as allotment of smaller areas to be made a result of incompletely putrefied meat only after clearance by the Fisheries De- is a matter of grave concern. Pollution partment through proper licensing sys- due to retting of husks, effluent dis- tem. Policy change by the State Govern- charged from industries and environmen- ment may include clam fishing under the tal hazards caused by the effluent re- Fisheries Department and exend all leased from shrimp peeling sheds in and rights and benefits to the clam fishers, around the Vembanad Lake has become similar to the coastal fishing communi- a major reason for the decrease in clam ties. Also, extend welfare measures to the production. clam fishers who have been traditionally involved in this practice. To enhance the The swarming/clogging of several value of meat, market promotion and ex- areas of the Lake by the African weed tension activities may be made by the Salvinia auriculata and the water hya- State Fisheries Departments and Export cinth, Eichhornia crassipes hampers the Promotion Department. fishing activities of the clam fishers for nearly 2-3 months. Alternative uses such as clam pickle, clam curry, clam soup and also for use as Lack of awareness regarding the poultry feed, fish feed etc. may be pro- nutritive value of the clam meat, absence moted. Some effective control measures of an organized marketing system, un- may be adopted to prevent pollution as explored potential for the export market well as clearance of weed to rejuvenate etc. are other factors limiting the black the Vembanad Lake as a whole.

90 Black clam fishery 91

The black clam fishery in Vembanad velopment and management of this valu- Lake does not show any sign of over-ex- able fishery of Vembanad Lake. ploitation at present. However, there are Acknowledgements clear signs of non-sustainability of this resource in the long run as indicated The authors are thankful to the Sec- above. Evaluation through extensive sur- retaries of the Clam Co-operative Socie- veys of the total standing stock of the ties and the private dredging companies black clam in the lake, the potential stock, for providing necessary information. The the sustainable levels of exploitation and assistance rendered by Shri P.S. the socio-economic impacts of the factors Alloycious in the collection of data for the affecting the clam exploitation from the preparation of this review is acknowl- lake are the urgent need of the hour. edged. Policy changes and management meas- References ures could be developed based on these evaluations. It is also necessary to cre- Achary, G.P.K. 1988. Characteristics of clam resources of Vembanad Lake - a case ate awareness among the clam fishers, study. Bull. Cent. Mar. Fish. Res. Inst., on the depletionary effects of over-fish- 42 (10): 10-13. ing, indiscriminate exploitation of seed clams, value-added products etc. Fishery Kunjukrishna Pillai, V. 1991. Studies on the management measures such as relaying, hydrobiology and pollution of the mixed farming with shrimps, establish- Vembanad Lake and adjacent waters. Ph. ment of clam sanctuaries and strict leg- D.thesis, Cochin Univ. Sci. and Technol., islative measures to control pollution, il- 148 pp. legal transport of shell, indiscriminate Rasalam, E.J. and M.J. Sebastian 1976. The exploitation of seed clams, illegal fishing lime shellfisheries of the Vembanad of live and fossil clams will provide the Lake, Kerala. J. Mar. Biol. Ass. India, impetus for the long-term sustained de- 18 : (2) 323-355.

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