Phuket Marine Biological Center Special Publication 25 (1): E1-SE (2001) 51 Tagging and recapture experiments in the Indian sacred chank, Turbinella pyrum along the Gulf of Mannar and Palk Buy,India A.P. Lipton & M. Selvakku Lipton, A.P. & M. Selvakku. 2001. Tagging and recapture experiments in the Indian sacred chank, Turbinella pyrum along the Gulf of Mannar and Palk Bay, India. - Phuket Marine Biological center special Publication 25(1): 51-55. Concomitant to the heavy demand of the sacred chank, Turbinellapyrum, several methods of large-scale exploitatiory including bottom trawling, take place in the Palk Bay and Gulf of Mannar regiory leading to depletion of chank resources. The natural growth of the chank is not known. Tagging and recapture experiments were therefore conducted. Chanks were brought to the laboratory, reared in a flow-through system, and conditioned before tagging with'Letro' labels attached to shells withAraldite. The measured and tagged chanks were released at specific sites in Gulf of Mannar and Palk Bay. Tagging and recapture data from 7994 to 1997 showed that in the natural habitat the increase of average Maximum Shell Diameter (MSD) ranged from 6.6 to 7.s mm. out of 7046 chanks tagged- the recovery ranged from8.7 to 71.5 %. A.P. Lipton. vizhinjam Research Centre of C.M.F.R.I. vizhinjam-69s 521,lndia M. selaakku. Mandapam Regionsl Centre of C.M.F.R,I Msrine Fisheries, P.O., PIN 523-520, India. INTRODUCTION depletion of population of chanks in the The sacred chank, Turbinella pyrum is a traditional chank bed areas. Although there gregarious, large, marine gastropod and it's are reports about the anatomy of chanks dwelling places form distinct chank beds (Moses 7923),the growth rate of chanks in the (Nayar & Mahadevan 7974; Lipton et aL traditional chank bed areas is not known. The 7996a). In addition to the ornamental aim of the present study is to determine the purposes, the recent demand for chank shells, natural growth rate of chanks by the tagging flesh and operculum has led to the increased and recapture studies. exploitation chank flesh is rich in protein and minerals (Chari 1966) and compares favorably MATERIALS AND METHODS with fishes. In the live condition the shell of Chnnk collections. - Chanks were periodically the chank is covered by a thick periostracum, collected from various chank beds in the Gutf which is brown in coloul, soft and velvety, and of Mannar by employing professional chank which easily peels off after the animal dies. divers. Chanks were also obtained from The shell is milky white. trawlers (as bycatch). Observations and In spite of restrictions imposed by the discussions with the traditional chank divers respective state Fisheries Departments, indicate the occurrence of about five rich exploitation of chanks by long-lines in Kerala chank beds and twelve sparse chank beds in (Appukuttanet al.7980) and by modified trawl the Gulf of Mannar area. nets along Rameswaram coasts in Tamil Nadu Measurements. - The total length and (Lipton et aI.7996 b) have been reported. The Maximum Shell Diameter (MSD) were intense bottom trawl activities also led to measured using Vernier caliper (Mitutoyo - 52 Tropical Mnrine Mollusc Programme (TMMP) made in Japan) and expressed in mm. The live chanks, they were brought to the laboratory weight was recorded using a top pan for further analysis. Using Vernier calipel, the electronic balance. length and maximum shell diameter were Acclimation nnd maintennnce of liae chanks in determined. The growth per year was subse- the laborntory. - Facilities for acclimating and quently calculated in terms of MSD. maintaining the live chanks were created at the Mandapam Regional Centre of Central RESULTS AND DISCUSSION Marine Fisheries Research Institute (CMFRI), Chsnk collection at Mandapam adjoining the Gulf of Mannar. In Rameswaram, the depth ranges from 5 to Sea water used for the flow-through system 6.5 m with mixed substrata including dead was drawn from the Gulf of Mannar. The corals and sand mixed with mud and algae. water exchange in the holding tanks ranged In addition to the traditional practice of chank from 1 to 1.5 litre per min. The bottoms of the diving, chanks were also exploited using a FRP tanks were filled up to L0 cm of sand, modified trawl net (: chanku madi). The which was periodically replenished and details are presented by Lipton et al. (7996b). replaced to maintain the sediment and water Bottom biota are disturbed by the operation quality. The water quality was monitored of such modified trawl nets (which comprise periodically. In all the tanks, water level of 50 large number of sinkers). Discussions with the cm was maintained. The chanks were fed ad traditional chank divers revealed that in libitum with lle Donax sp. Dust particles, Rameswaram area six traditional chank beds impurities and remains of the feed were ('paars') adjacent to the coral reefs have been removed twice daily. totally destroyed by the operation of the Sea water in the rearing system. - The sea water 'chanku madi'. During the chank diving samples from the rearing facilities were season, which extends from ]anuary to March, analysed for pH, salinity, and dissolved they find almost barren seabed, which r,t'a5 oxygen, using standard methods of APHA. earlier flourishing with chanks, holothurians, The water temperature was recorded at the corals, and other molluscs. In addition, the culture facility twice daily. sizes of chanks obtained from these chank bed Tagging experimenfs. - During the experiments areas are also decreased and thus fetch lesser a total of 1086 sacred chanks were tagged prices. using Letro labels attached with Araldite. In Mandapam, chanks are taken at depths Initially, the periostracum to about 1.5 x 3.0 ranging from 4 to 5 m. Dead coral reefs u'ith cm was peeled using a fine scalpel. The'Letro' sand and molluscan shells constifute the chank (plastic) labels with code number embossed bed substrata. In Vedalai, chanks are available on them were fixed in the peeled area with at depth ranging from 4.5 to 6 m. Here, the 'Araldite' glue. Of these, 1046 chanks were substrata are dead coral reefs and sand n-ith taken to chosen chank bed areas and sea mud along with live corals. In Kanniraja- ranched in the Gulf of Mannar and Palk Bay puram, chanks and egg capsules are available to record their natural growth. The rest of the at depths ranging from 6.5 m to 72 m. The chanks were maintained in the laboratory for substrata are dead corals with large sand breeding and other biological studies. At the particles, empty shells of molluscs, and large time of the release of chanks in the natural coral reefs. Presently, Kannirajapuram is the habitat, the depth, hydrological conditions one of the important chank bed areas in the prevailing in the area of release were recorded. Gulf of Mannar. Wide publicity through newspapel, radio and printed pamphlets was given to return the tagged and recovered chanks. After receiving Measurem " r" Wl:{riJJJ'i. oistingui sh- the information regarding recovery of tagged ed varieties of the chank aiz., Tw'hitrcIln^, L)ttrunl Phuket Mqrine Biological Center Special Publication 25 (1): 57-55 (2001) 53 1. Principai characteristics t!1" of 4 varieties of sacred chank, Turbinellapyrum collected from the Gulf of Mannar. Measurements Length Variety Principal features MSD Ratio (mm) (mm) length: breadth 1. Elongated spire Turbinella pyrum var. 2. Fusiform shape acutn 3. Convex profile of whorls 101.5 !74.58 50.18 + 8.49 2.03 4. Abundant l. Short Turbinella pVrum var. spire 2. Globose shape obtusa 98.05 t 10.05 53.8 + 4.3s 3. Less abundant 1. Elongated spire Turbinella pyrum var. 2. Fusiform shape comorinensis 3. Straight profile of whorls 103.0 51.0 4. Rare 1. Spire moderately elongated Turbinellq pyrum vat. 2. Shape between fusiform & globose irupiraai 108.6 ! 74.68 55.65 r 3.13 1..96 3. Shell colour usuallv saffron 4. Less abundant vaL acuta and Turbinella pyrum vaL obtusa.In Tgble 2. Yearly averages (range of vaiues TggS- Turbinella pyrum var. qcuta, the profile of 1997) of temperature, pH, salinity, and dissolved whorls in the spires is convex. In the case of oxygen measured in sea water from the Gulf of Turbinella pyrum var. lbtusa, the profile of Mannar. whorls in the spires is very short and the shell Temperature ("C) measured at 0900 hrs appears as a'top'. TWo other varieties could 7995 20.00 + 0.77 to 29.58 + 0.70 be distinguished viz., Turbinella pyrum var. 7996 23.52 + I.70 to 30.02 + 1.1S co m or in ens is and Turb in eII a py r um v ar ir up ir au i. 7997 24.30 + 0.48 to 29.47 + However, it could be inferred from the 0.73 collection data that the two latter varieties pH formed less than 5.0 % of the total chanks 1995 8.19 + 0.00 to 8,25 + 0.02 collected by divers or landed by trawlers. 7996 7.69 + 7.24 to 8.95 t 0.00 Details of the characters of the four 1997 8.74 + 0.05 to 8.19 t 0.01 distinguishable varieties are presented in Salinity (ppt) Table 1. 7995 32.45 + 1.50 to 35.55 + 7.19 7996 29.53 ! 7.20 to 35.77 t 0.13 Sea zuqter in the rearing system 7997 31.18 + 7.77 to 34,98 + 0.72 Measurements of the selected parameters of sea water (from the Gulf of Mannar) are D.O. (mg/l) measured at 0900hrs presented in Table 2.