ISSN 0254-380 X "y.*?*! iv ^ a^i. ERIE$ FORMATION SERYKE No. 94 THE PRAWN, FISH AND MOLLUSCAN SEED RESOURCES ALONG THE KERALA AND TAMILNADU COASTS* Introduction Six teams of scientists and technical personnel operated the project from six different research centres The Central Marine Fisheries Research Institute, along the coast namely Calicut, Cochin, Vizhinjam, Cochin launched a pioneering research project during Tuticorin, Mandapam and Madras. Sampling stations the period 1976-'80 on the seed resources of commer­ were fixed all along the coastal area at every 6 to 10 km cially important prawns, fishes and molluscs in the distance. However, within the estuaries and backwaters surf waters, estuaries and backwaters of Kerala and sampling was carried out at shorter intervals of distance. Tamilnadu. The objective of the project was to gain Along with the collection of seed samples, environ­ precise information regarding occurrence and quanti­ mental parameters such as temperature, salinity and tative abundance of seed, their spatial, seasonal and dissolved oxygen were also monitored. While a variety diurnal variations, abundance in relation to lunar perio­ of gears were used for the qualitative studies, the quan­ dicities, influence of environmental features and pollu­ titative estimates were made by employing the bucket- tion on them and areas suitable for brackishwater cul­ scoop net method in the surf area and a specially desi­ ture. gned quantitative seed sampler developed at the Insti­ tute in the estuaries and backwaters. Voluminous The investigations were carried out in three phases. data were collected during the investigations and the During the first phase (1976-'78) emphasis was given results are being published in the form of a bulletin. to the seed resources of the surf area, followed by that The present account brings out the salient findings of in the estuaries and backwaters. A total of 246 stations the studies. were covered all along the coasts at monthly interval for the purpose. During the second phase which went 1. RESULTS OF FIRST PHASE OF SURVEY on for another year (1979) the studies were centred in the estuaries and backwaters, and 49 stations were Areas covered covered, again at a monthly interval at four regions. The third phase of the survey which was completed in The surf sampling for the seed resources was carried one year (1980) was devoted for an intensive study on out in Kerala from north to south at Kasaragod, Bekal the diurnal variations in seed abundance and on the Fort, Thaikadapuram, Ettikulam, Mattul, Azhikal, influence of moon on their occurrence and abundance. Azhikode (north), Cannanore, Dharmadam, Tellicherry, For this purpose one centre was selected in each of the Mahe, Badagara, Iringol, Tikkodi, Quilandy, West six regions and quarterly diurnal sampling at hourly Hill (Calicut), Beypore, Kadalundi, Parappanangadi, interval was carried out during full, half and new moon Tanur and Paravana in the Kasaragod-Ponnani Region; phases occurring sequentially in a month. Ponnani, Puthuponnani, Mannalamkunnu, Chavakkadu, • This work was carried out under the Institute Project 'Survey Vizhiiyam K. Prabhakaran Nair of Fish, Prawn and Molluscan (bivalves) Seed Resources of Kerala (1976-'80) and Tamil Nadu'. Personnel associated with the project: S. Lazarus (1976-'80) Project Leader : E.G. Silas (1976-'80) Tuticorin P. Bensam (1976-'77) & Project Associates: (1979-'80) Calicut : R.S. Lai Mohan (1976-'80) S. Shanmugom (1976-'80) K.V. Somasekharan Nair Bastin Fernando (1976-'80) (1976-'80) ^, . N. Gopinatha Menon (1977-'80) Mandapam K.M. Ameer Hamsa (1976-'80) P. Ramadoss (1976-*80) P. Nammalwar (1976-78) V. S. Rengaswamy (1976) R. Thiagarajan (1977-'80) K. Nandakumaran (1978-'80) G. Nandakumar(1977-'80) Cochin : K. J. Mathew (1976-'80) Madras K. Rangarajan (1976-'80) G.S. Daniel Selvaraj (1976-'80) M. Rajagopalan (1976-'80) K. Rengarajan (1978-'80) . K.S. Sundarara (1976-'78) K. N. Gopalakrishnan T. Dhandapani (1979-'80) (1976-'80) Chetwai, Vadanappally, Nattika, Kaippamangalam, Valinokkam, Palayar, and Mayakulam in the Kanya- Vemballoor, Azhikode (South), Narakkal, Fort Cochin, kumari-Keelakarai Region; Kanjiramgudi, Periapatnam, Manassery, Chellanum, Anthakaranazhi, Arthumkal, Seeniappa Dharga, Pamban, Chinnapalam, Kadarsa- AUeppey, Ambalapuzha, Thottappally, Thrukkunna- pad, Rameswaram Road, Pillaimadam, Athankarai, puzha, Ayiramthengu, Chavara and Neendakra in the Kottakkarai, Vattanam, Pasipattinam and Sundarapan- Ponnani-Neendakara Region; Sakthikulangara, Than- diapattinam in the Keelakkarai-Sandarapandiapattinam gassery, Paravur, Edava, Perumathura, Veli, Panathura, Region and Muthupet, Vedaranyam, Uppanar, Adappar, Vizhinjam, Adimalathura, Puthiyathura to Parilhiyur Harichandranadhi, Vellaiyar, Kaduvaiyar, Vettar, in the south and in Tamilnadu on the southwest coast Thirumalayar, Arasalai, Virasolanar, Cauvery, Coleroon from Thengapattinam, Enayam, Melmidalara, Colachel, Killai, Vellar, Pennaiar, Varanganadhi, Kadapakkam, Kadiapattinam, Muttom, Azhikkal, Rajakkamangalam, Palar, Kovalam, Adayar, Ennur and PuUcat in the Manakudi, Kanyakumari west and Kanyakumari point Muthupet-Pulicat Region. in the Neendakara-KanyakumariRegion; Chinnamuttom, Leepuram, Variyoor, Vattakottai, Uvari, Periathalai, Hydrological features Alanthalai, Narippur and Yerwadi in the Kanyakumari- Keelakkarai Region and Keelakkarai, Sethukarai, Mu- A summary of the results obtained on the environ­ thupet, Puthumadom, Seeniappa Dharga, Vedalai, mental features for the respective zones (zones 1-18) Mandapam (Gulf of Mannar), Thonithurai, Pamban, is given in Table 1. Temperature, salinity and dissol­ Kundugal, Naduthurai, Rameswaram Road, Hare ved oxygen were found to vary considerably especially Island, Manoli Island, Krusadi Island, Shingle Island, in the estuarine and backwater areas and were influ­ Chinnapalam, Rameswaram, Thangachimadam, Pam­ enced by several factors such as seasons, tide, rainfall, ban, Thonithurai, Mandapam (Palk Bay), Munaikadu, freshwater discharge, pollution and nearness to bar Pillaimadam, Dhargavalasai, Athankarai, Mudiveeran- mouth. pattinam, Devipattinam, Karangadu, Thondi and Sun- darapandiapattinam in the Keelakkarai-Sundarapan- The temperature varied over a wide range in the diapattinam Region. No sampling was carried out in surf area along both west and east coasts and the varia­ the surf area in the Muthupet-Palicat Region. tion was between 21 and 36°C. The maximum tem­ perature was observed in Tuticorin and the minimum at Keelakkarai in Tamil Nadu. In the estuarine areas The stations in the estuarine and brackish water eventhough the minimum remained the same in the areas worked out along the coast for regular studies surf area the range was still higher and the maximum starting in Kerala from north to south and around registered was 40°C in some of the salt-pans in Tuti­ Kanyakumari to north upto Pulicat Lake were Chand- corin area. Along the Kerala coast, however, the maxi­ ragiri, Bekel, Nileswaram, Punnakadavu, Cherukunnu- mum temperature noted in estuaries was 37°C. The Thavam, Mattul, Valapattanam, Azhikode (north), relation between temperature and salinity was more Nadal, Anjangadi, Koduvallypuzha, Mahe, Iringol, pronounced in the interior waters than the surf region. Kottakkal, Chovai, Korapuzha, Kallai, Elamarakadavu, Manthalakadavu, Beypore, Kadalundi, Poorapuzha and In the surf area along the Kerala coast the salinity Chamravattom in Kasaragod-Ponnani Region; Ponnani, ranged between 11 and 37 %„ while in Tamilnadu the Puthuponnani, Chetwai, Azhikode (south), Kottapuram, range was between 9 and 41 %^. In many estuaries and Nayarambalam, Puthuvypeen, Thoppumpady, Perum- backwaters, salinity came down to near fresh water balam, Anthakaranazhi, Thanneermukkom, Muhamma, condition especially during southwest monsoon in Thottappally, Ayiramthengu and Ashtamudi in the Kerala. However, in summer the values almost equalled Ponnani-Neendakara Region; Paravur, Edava, Anjengo, with the marine conditions. In the estuaries and back­ Veli, Panathura, Adimalathura, Karichal, Parithiyur, waters of Tamilnadu eventhough low values in saUnity Thengapattinam, Melmidalam, Colachel, Puthoor, were observed during the rainy season, very high sali­ Chinnavilai, VaUiar, Azhikkal, Rajakkamangalam and nities, often reaching upto 144 %„ were also recorded Manakkudi in the Neendakara-Kanyakumari Region; in and near the salt-pan areas. Thattarippu, Kuttapuli, Perumanal, Uppar, Hanuman Nadhi, Idinthakarai, Koothankuzhi, Athankarai, Mana- The observed values of dissolved oxygen in the pad, Thiruchendur, Kayalpattinam, Arumuganeri, surf and estuaries showed great variations in both the Punnaikayal, Palayakayal, Mullakad, Muthiapuram, states. Low values of oxygen were generally noticed Tuticorin south, Karapad, Arasadi, Melarasadi, Kalani- in the brackish water areas especially where environ­ pattu, Kallar, Kallurani, Vaipar, Vembar, Mookaiyoor, mental pollution occurred. Surprisingly enough low Table 1. Hydrological conditions observed in the various zones of observations Zone Zones SURF ESTUARY No. Temp. CO Sal.(%„) 0,(m il/l) Temp. (°C) Sal. (/oo) o, (ml/1) Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. 1. Kasaragod-Azhikkal 24 34 25 36 1.6 6.1 26 36 1 35 2.7 2. Azhikkal-Badagara 26 35 11 36 2.6 5.7 27 36 1 35 — 6.8 3. Badagara-Beypore 26 35 24 36 2.7 5.7 27 34 1 36 0.5 6.2 4. Beypore-Ponnani 27 33 30 36 2.4 6.3 23 35 — — 2.1 6.2 5. Ponnani-Nattika 24 35 13 36 2.4 6.3 23 35 0 36 2.5 5.6 6. Kaippamangalam-