With a view to finding out the feasibility of Lakshadweep lagoons for cultivation of Gracilaria edulis in Minicoy experimemal culture has been undenaken at four sites. Very encouraging results indicating high potential of about 8.1 fold increase for this species in the lagoon evironments of Minicoy was obtained. Seasonal variations in the growth of the culture seaweed is high-lighted in this account indicating favourable seasons and potential sites

Chennubhotla, V S Krishnamurthy

Kaladharan, P

Kaliaperumal, N

Rajagopalan, M S

CMFRI Digital Repository

Seaweed Re,. Utiln 14 (2): 109-113 SEASONAL VARIATIONS IN PRODUCTION OF CULTURED SEAWEED GRAClLARIA EDULTS (GMELIN) SILVA IN MINICOY LAGOON (LAKSHADWEEP) V.S.K. Chennubhotla, P. Kaladharan, N. Kaliaperumal and M.S. Rajagopal Central Marine Fisheries Research Institute Cochin-682031 ABSTRACT With a view to finding out the feasibility of Lakshadweep lagoons for cultivation of Gracilaria edulis in Minicoy experimemal culture has been undenaken at four sites. Very encouraging results indicating high potential of about 8.1 fold increase for this species in the lagoon evironments of Minicoy was obtained. Seasonal variations in the growth of the culture seaweed is high-lighted in this account indicating favourable seasons and potential sites. INTRODUCTION Seaweed Culture Technology At present it is estimated that about 40,000 tonnes (fresh wt) of seaweeds are annually harvested for extraction of phycocolloids agar-agar and algin. However it has exceeded the renewable capacity especially along Tamil Nadu coast and hence the need to cultivate the same has arisen. (Anon, 1987). Since 1972, the Central Marine Fisheries Research Institute (Chennubhtla et.al .1977 & 78) and Central Salt and Marine Chemicals Research Institute (Raju & Thomas, 1971, Krishnamurthy etal. 1975) have been involved in the experimental field cultivation of agar-yielding G. acerosa and G, edulis and ag2Coid yielding Hypnea va/entiae and Acanlhophora spicifera, algin yielding species such as Sargassum and Turbinaria in near shore areas of Gulf of mannar and Palk Bay through vegetative propagation methods by inserting the fragments of the mother material into the twists of coir rope nets. Out of these, encouraging results were obtained with G. edulis, G. acerosa and A. spicifera. The culture technology involved tieing of coir or HDP rope net seeded with seaweed, to fixed poles in the inshore waters or ponds. The plants reach harvestable size after 60 days. G. edulis cultured in the near shore areas of Gulf of Mannar and Palk Bay using coir ropes and HDP rope nets yielded an avarage of 3 fold increase after 60 days (Ch~nnuabhotla el al 1978) G.acerosa fastened to coral stones with the help of iron nails reached harvestab1e size after five months recording 3 fold increase and sometimes manifold (Chennbhotla el al 1977; Subharamaih el al 1975). A spicifera cultured in ponds over coir rope and HDP rope nets yielded a 3.6 and 2.3 fold increase after 45 days and 70 days respectively (Anon 1977). With a view to finding out the feasibility of Lakshadweep lagoons for G. edulis culture, for the first time, the experimental culture has been uncte[laken since 1990 in Minicoy (Lat go 1 TN and Long 73° 04') at four sites, viz, Near Helipad, Light House, Fisheries Jetty and Navodaya school. HARVEST PARTICULARS OF GRACILARIA EDULIS AT MINlCOY Species Place of Date of Seed material Date of Crop Increase in Percentage growth cultivated cultivation introduction introduced (kg) harvest & harvested yield of seaweed/day no.of days (Wet WL in kg) (I) (2) (3) (4) (5) (6) (7) (8) (I) G. edulis Fisheries 12-3-90 0.250 13-4-90 0.800 3.2 fold 3.953 (Kavaratti Jetty (one long line) (30 days) material) (2) -do- -do- 13-4-90 0.250 28-5-90 1.475 5.9 fold 4.023 (remnets (45 days) on long line) (3) -do- -do- 13-4-90 0.800 11-6-90 6.450 8.1 fold 3540 (4) -do- -do- 12-3-90 3.750 9-5-90 11.850 3.2 fold 1.936 (one net) (60 days) (5) G. edulis -do- 27-3-90 2.000 9-5-90 3.150 1.6 fold 1.015 (Mandapam (one net) (45 days) material) (6) G. edulis LightHouse 16-3-90 1.600 10-5-90 5.980 3.7 fold 2.222 (Kavaratti (one net) (60 days) material) (7) G. eduHs -do- 29-3-90 2.000 10-5-90 3,470 1.7 fold 1.232 (Mandapam (one net) (45 days) material) (8) G. edulis Fisheries 27-3-90 1.800 26-7-90 6.600 3.7 fold 1.071 (Mandapam Jetty (one net) (122 days) material) (9) ·do· -do- 9-5-90 2.000 26-7-90 12.200 6.1 fold 2.315 (79 days) Second harvest (10) -do· ·do· 13-6-90 0.700 7-9-90 4.000 5.7 fold 2.024 (one long line (87 days) 14m. length) (II) G. edulis ·do· 9-5-90 3.000 10-7-90 6.600 2.20 fold 1.259 (Kavaratti (63 days) Second material) harvest (12) -do- -do- 9-5-90 2.900 7-9-90 6.250 2.2 fold 0.631 (one net) (122 days) (13) ·do- Navodaya 26-10-90 0.600 31.12.90 4.300 7.1 fold 3.029 (net) (66 days) (14) ·do· -do· 26-10-90 0.600 31.12.90 1.480 2.4 fold 1.377 (net) (66 days) (15) ·do· Fisheries 25-10-90 1.000 31.12.90 2.300 2.3 fold 1.251 (67 days) (16) ·do· ·do· 25-10-90 1.000 31.12.90 4.050 4.05 fold 2.110 (67 days) 112 Initially the seaweed C. edulis was not available in the wild in Minicoy Lagoon. Hence the same was tranSported from Mandapam (east coast) and Kavaratti, the Capital of Lakshadweep group of Islands. The seed material was introduCed in the long line ropes, coir nets and nylon nets (HDP rope nets) in all the 4 culture sites. The growth of C. edulis at fisheries jetty and near Light House was found to be encouraging and the plants reached harvestable size after 45 days and 60 days growth. The remnants of the plants left on the nets and long line rope after fITSt harvest were allowed to grow and a second harvest also was made after another 60 days. A maximum yield of 8.1 fold increase over the seed material was obtained after 60 days on a long line rope near fisheries jeuy (Table I) As rough conditions prevailed during mensoon season, the calture operations were discontinued at all the places except near Fisheries Jetty. The nets introduced at Fisheries Jetty were harvested in July and September "90 after the plants had attained the harvestable size and the yield was found to be 6.1 and 5.7 fold. In the other nets the growth was nO! encouraging. The yield of the crop in the nets would have been more than that was observed, but for the haeavy grazing by the fishes of the genus Siganus from June to September The grazing of G. edulis by the species of Siganus is not an uncommon fearure, as it was already reponed by James el.a/1980 on the east coast. During October culture operations were started at all four culrure sites. The growth of C. edu/is near the sites at Navodaya School and Fisheries Jetty was good. The harvest was taken after 66 days at both places, with 7.1 fold increase in one net and 2.4 fold increase in another at the former place while the yield was 2.3 and 4.5 fold in the two nets at the lauer site (Table. I). At the other two sites, the growth was not encouraging due to heavy sedimantation and epiphytic growth of Acanthophora spicifera. At Navodaya School si te also, the epiphytic growth of the blue green Lyngbya was observed, but it did not hamper the growth of C. edulis in the nets. Another important feature is that the grazing-hitherto observed at fisheries jetty was minimized during December 1990, thus allowing the seaweed crop to thrive well on the nets. During January and February'91 also the grazing was not much at Fisheries jetty and as a result the seaweed growth was found to be good. The percentage growth rate of seaweed per day was calculated using the formula given below and the results are presented in Table I: d" = 0V -JW .l l /t -I x 100. A notable obervation is the settlement and colonization of C. edulis on the seagrass beds in the vicinity of Fisheries Jetty and Navodaya School sites in the lagoon. The same grew to harvestable size and got established in the lagoon thus bringing the Minicoy on the map of the Graci/aria growing areas. The grazing observed on the crop in the nets was simutaneouly noted on the natural crop also. In conclusion , it can be said that the present studies have revealed a great potential for the growth and culture of C. edulis in Minicoy lagoon. It has also indicated that out of the four culture sites tried, two viz Fisheries jetty and Navodaya school are very productive with regard to C. edu/is culture. From the foregoing account, it can be said that seasonwise, best results can be obtained during pre and post monsoon seasons and during the monsoon season turbulance causes heavy sedimentation 113 on the growth of seaweed and makes the infrastructure used (i.e culture nets etc) for cultivation, very unstable. Hydrological conditions of the areas of study were monitored throughout and the correlation of the same with seaweed growth will be discussed separately. Acknowledgements The authors wish to thank Dr. PSBR James, Director, CMFRI, Cochin for his keen interest in these investigations. References Anon 1987 Seaweed Research & utilization in India CMFRI Bulletin 41 pp. Chennubhotla, V.S.K., S. Kalimuthu, M. Najamuddin & M. Selvaraj 1977 Field culture of Gelidiella acerosa in the inshore waters of Gulf of mannar. Supplement to J. Phycol. vol.13, Abstract No.454. Chennubhotla, V.S.K., N. Kaliaperumal & S. Kalimuthu 1978 Culture of Graci/aria ed"lis in the inshore waters ofGuU ofMannar (Mandapam) India. J. Fish. 25 (1 & 2) 228-229 Cheuh, e.T. & C.C. Chen 1982 Seaweed economics in Taiwan In R.T. Tsuda & Y.M. Chiang (Eds.) Proc. Coop. Sci. Sem. Cultivation and utilization of ecomomic algae, June 1978 James, PSBR., VSK. Chennubhotla & J.x.Rodrigo 1980 Studies on the fauna associated with the culture of seaweed Graci/aria edulis Proc. Symp. coastal Aqllaculture-MBAI, Cochin Krishnamurthy, Y., P.V. Raju & P.C. Thomas 1975 On augmenting seaweed resources of India J. marbiol.Ass.lndia, 17(2):181-185 Pizarro, A & N.Barrales 1986 Field assessment of two methods of planting of the agar containing seaweed, Graci/aria, in northern Chile Aqua culture 59:31-44 Raju.P.V. & P.C. Thomas 1971 Experimental field cultivation of Graci/aria edulis (Gmel.) Silva Bot mar. 14(2): 71-75 Ren GZ., J.e. Wang & M.O.Chen 1984 Cultivation of Graci/aria by means of low rafts Hydoi%gia 1161117:72-76 Ren. GZ. & M.S. Chen 1986 The e(fect of temperature on the growth and development of Graci/aria asiatica, Oceano Limnol.Sin 17:292-300 Santelices. S & N. Vgane Production of Chile Graci/aria: Problems and perspectives in Proc.12 Int. Seaweed Symp. Sao Paulo, Brazil, August, 1986 Tseng, C.K. 1989 Material on extended seaweed component to be incorporated in "seafru ning" prepared for NCM/fPR-Aug. Yang S.S. 1982 Seasonal variation of the quality of agar-agar pTOliuced in Taiwan. In R.T. Tsuda & Y.M Chiang (Eds.) Proc. Coop. Scisem. Cultivation ..... algae, June 1978, pp. 65-80 Subharamaiah, K., K. Rarna Rao, P.C. Thomas, MRP Nair, B.V. Gopal & V.R. Nagulan 1975 Cultivation of Gelidiella acerosa Salt Res. Ind. 1I (I): 33-36 S.WEED/NEW/CHEENU 

Seasonal variations in production of cultured seaweed Gracilaria edulis (Gmelin) Silva in Minicoy Lagoon (Lakshadweep)

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Seasonal variations in production of cultured seaweed Gracilaria edulis (Gmelin) Silva in Minicoy Lagoon (Lakshadweep)

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