THE STUDY OF POPULATION DENSITY OF MARINE MOLLUSCS FROM MID COAST OF RATNAGIRI DISTRICT.

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1 THE STUDY OF POPULATION DENSITY OF MARINE MOLLUSCS FROM MID COAST OF RATNAGIRI DISTRICT. Shaikh A. M. and Bhalerao R. S. Department of Zoology, C. S. College of Arts, Commerce and Science Khed, Dist. Ratnagiri (M. S.). ABSTRACT Population density of marine mollusca from Ratnagiri coast was studied. Three study areas were selected from Ratnagiri district like Harne, Dhabhol and Burundi. Population Density of gastropoda, bivalve and cephalopoda was found to maximum in Burondi followed by Harne and Dabhol respectively. In Burondi, coastline is less as compare to Harne and Dabhol but there is no any human activity, fishing activity due to which there may be maximum population density of studied mollusc, while in the Harne region fishing activities may disturb molluscan habitat whereas Dabhol study area having Ratnagiri Power house might be impacted population density in this region.concerned to seasonal variation, rich density was found in all study areas during winter and summer season; in Konkan region has a good potential of mollusca population due to favourable environmental parameters, similar results have also shown by number of researchers that increasing trends of density from monsoon to afterwards. KEY WORDS: Density, molluscs, Ratnagiri Coast. INTRODUCTION Molluscans are one of nutritive and ornamentive phylum of invertebrate group. Mollusca form a major group which is not only an important link in food chain from primary to tertiary level leading to fish production but an edible source for coastal population. Beside they are utilized for ornamental trade, pharmacological products and in manufacture of lime and cement. The number of marine mollusc recorded from various parts of the world vary from 80,000 to 1,00,000 species (Subha Rao,1991). Today as matter of concern worldwide the molluscan fauna along with various others to provide biodiversity is declining every day from coastal areas as consequences of human interference. The impact of biodiversity loss on the functioning of ecosystem and their ability to provide ecological services has become central issue in ecology as reduced diversity may impair ecosystem. The present investigation has been taken up for assessing population density in order to know the present production potential of intertidal molluscs under the influence of well-established high degree of pollution along the mid-west coast of Maharashtra. The study may be useful in conservation and management of molluscan resources distributed in the intertidal zone of mid coast of Maharashtra. Various coastal lines are polluted due to industrial waste or effluents which comes along with waste water of different industries, which is one of cause to change population density as well as nutrient content (reference to flesh quality) of intertidal mollusc. Above discussed problems i.e. Tourism development, fishing activities also continuously disturbing molluscan habitat; ultimately overall impacting on molluscan world of mid-west coast. One of newly ongoing project i.e. Ratnagiri power house at Dabhol creek might be affecting on population density and nutritional content. Seasonal variations in population density have been studied by many workers from known region of west coast of Maharashtra. However, comparatively little data is available from interior mid-west coast; which is supposed to be untouched regarding research activities due to remote area and ghat sections. So far more intentionally this area was selected for study. MATERIALS AND METHODS Study Area:-With the help of map of Konkan region firstly continuous visited mid coastline of Konkan and considering title and objectives of present project, selected three study areas like Harne, Burondi and Dabhol. Harne, Burondi and Dabhol are small coastal villages having rocky, sandy coastal lines which offers fish landing supposed to small fish port. These villages are at remote with ghat section and extreme interior so untouched from research activities are situated 150 km from Ratnagiri and 150 km from Mumbai. Topographical distance between selected area i.e. Harne to Burondi 05 km and Burondi to Dabhol 05 km. Harne is one of heavy economic zone due to fish catching and landing activities; similar importance of Burondi and Dabhol. Dabhol is additional important for study because Ratnagiri Power House is situated in this region which may be affecting population density and flesh quality of intertidal mollusc. Present investigation was carried out during the period of June 2009 to May The selected areas were visited at peak of each season i.e. July 2009 for monsoon, Nov 2009 for winter and April/May 2010 for summer season. Each study areas were visited one after another for to record population density. Vol. 1 No. 2 (2012) ISSN: X (Print); (Online) 2012 DAMA International. All rights reserved. 34

2 Population Density: Population in 1m 2 area was considered to assess the density. Average of ten random samples of molluscan species each from 1m 2 area at marked station of fixed transect were measured and is expressed as number of mollusc per m 2. RESULTS AND DISCUSSION During the present study 28 species of gastropoda, 06 species of bivalve and 04 species of cephalopoda were found from Harne, while 16 species of gastropoda, 03 species of bivalve and 04 species of cephalopoda were recorded from Burondi, whereas 14 species of gastropoda, 03 species of bivalve and 02 species of cephalopoda were found from Dabhol. Population density of mollusc increase in winter and summer season from all studied areas. Table 1. Study Area: Harnai Sr. Seasonal data of population density (Number/m 2 ) Name of Species No. 1 Planaxis sulcatus Drupa Babylonia spirata Natica picta Garynieum natator Littorina Bursa tuberculata Thais rudolphi Katheria Cirethium morus Nurita polita Cellana rita Nassarius thersites Crossostrea Meretrix meretrix Katelysia opima Saccostrea Perna viridis Arch granulosea Loligo dovacell 8 ton/day 12 ton/day 15 ton/day 21 Loligo vulgaris 150 Kg/day 175 Kg/day Octopus Kg/day Harne- Among 28 species of gastropoda, most abundant species on this study area was Planaxis sulcatus 150/m 2 in July increased to 190/ m, 185/m 2 in Nov and April respectively. This was followed by Drupa i.e.130/m 2, 168/m 2, 172/m 2 in July, Nov and April respectively. Babylonia spirata found to (110/m 2, 140/m 2, and 143/m 2 ) in July, Nov and April respectively as same pattern of variation in population density like above mentioned species. This was followed by Natica picta 90/m 2 in monsoon 102/m 2 and 107/m 2 in winter and summer respectively. Garynieum natator was species rank after Natica picta concerned to population density i.e. 78/m 2, 83/m 2 and 90m 2 in July, Nov and May respectively. Followings are the gastropod species are reported as per decreasing order concerned to population density. Littorina (60/m 2, 68/m 2, 70/m 2 ) in monsoon, winter and summer respectively. Bursa tuberculata (55/m 2, 58/m 2, 55/m 2 in monsoon, winter and summer respectively). Thais rudolphi ( 50/m 2, 52/m 2, 54/m 2 in monsoon, winter and summer), Katherina (45/m 2, 47/m 2, 46/m 2 in monsoon, winter and summer respectively). Cirethium morus (42/m 2, 44/m 2, 45/m 2 in monsoon, winter and summer season respectively), Nurita polita (25/m 2, 26/m 2, 25/m 2 in monsoon, winter and summer season respectively), Cellana rita (23/m 2, 28/m 2, 32/m 2 in monsoon, winter and summer respectively), Nassarius thersites (22/m 2, 24/m 2, 25/m 2 in monsoon, winter and summer respectively), remaining species were not found consistently so they are not considered. Concerned to Bivalva: Crossostrea was reported 280/m 2,298/m 2,320/m 2 in monsoon, winter and summer respectively. Meretrix meretrix found in monsoon abundant species i.e. 250/m 2 ; tremendous increase was found in winter i.e. 450 /m 2 Vol. 1 No. 2 (2012) ISSN: X (Print); (Online) 2012 DAMA International. All rights reserved. 35

3 again increased in summer i.e.510/m 2. katelysia opima was reported 240/m 2, 250/m 2 and 250/m 2 in monsoon, winter and summer respectively. Saccostrea was found to 225/m 2,231/m 2,239/m 2 in monsoon, winter and summer respectively. The population density of Perna viridis was reported 212/m 2, 218/m 2, 222/m 2 in monsoon, winter and summer respectively, whereas Archa granulosea was found to very less number i.e. 22/m 2 in monsoon, while these were not reported in winter and summer. Concerned to cephalopoda Loligo dovacelli reported an average 8 ton/day in monsoon, increased in winter (12 ton/day) and summer (15 ton/day). Loligo vulgaris was very less density on Harne coast i.e. an average 150 kg/day in monsoon, 175 kg/day in winter, while none of species found in summer season. As same manner occurrence of Octopus i.e. it was found only in winter season as an average 65 kg/day. Seasonal study of mollusca population density from Harne study area showed to increase in winter and summer season. Table 2. Study Area: Burondi Sr. No. Name of Species Seasonal data of population density (Number/m 2 ) 1 Planaxix sulcatus Gayrenium natator Natica picta Babylonia spriata Drupa Bursa tuberculata Katherina Thias rudolphi Trochus radiates Nassarius Cellana rata Katelysia opima Meretrix meretrix Saccostrea Loligo duvacelli 6 ton/day 8 ton/day 12 ton/day 16 Loligo vulgaris 4 ton/day 6 ton/day 5.9 ton/day 17 Sepia 3 ton/day -- 6 ton/day 18 Octopus Kg/day Burondi: Total 16 species of gastropod were reported from Burondi of which Planaxis sulcatus species was 175/m 2, 183/m 2, and 194/m 2 in monsoon, winter, and summer respectively. This was followed by Gayrenium natator i.e.168/m 2, 179/m 2, 183 /m 2 in monsoon, winter and summer season respectively. Natica picta was reported 163/m 2, 169/m 2, and 174/m 2 in monsoon, winter and summer respectively. Babylonia spirata was found to 154/m 2, 163/m 2, and 165/m 2 in monsoon, winter and summer respectively. Drupa was found to 140/m 2, 152/m 2, and 159/m 2 in monsoon, winter and summer respectively. Followings are the gastropod species reported as per decreasing manner concerned to population density. Bursa tuberculata (130/m 2, 139/m 2, 143/m 2 in monsoon, winter and summer respectively), Katherina (122/m 2, 129/m 2, 134/m 2 in monsoon, winter and summer respectively), Thias rudolphi (117/m 2, 122/m 2, 129/m 2 in monsoon, winter and summer respectively), Trochus radiates (98.m 2, 102/m 2, 112/m 2 in monsoon, winter and summer respectively), Nassarius (89/m 2, 92/m 2, 101/m 2 in monsoon, winter and summer respectively), Cellana rata (60/m 2, 73/m 2, 84/m 2 in monsoon, winter and summer respectively). Concerned to bivalves: Katelysia opima was reported 345/m 2, 356/m 2, and 369/m 2 in monsoon, winter and summer respectively. Followed by Meretrix meretrix (290/m 2, 320/m 2, 331/m 2 in monsoon, winter and summer respectively). Saccostrea (248/m 2, 252/m 2, 260/m 2 in monsoon, winter and summer respectively). Concerned to cephalopod: Loligo duvacelli was reported an average 6 ton/day in monsoon, increased in winter (8 ton/day) and summer (10 ton/day).this is followed by Loligo vulgaris an average 4 ton/day) in monsoon, increased in winter ( 6 ton/day), as similar average was found in summer season( is ton/day). Sepia was reported an average 3 ton/day, increased in summer 6 ton/day while none of Sepia was found in winter season. Octopus was reported only in summer season (April and May 2010) an average 50 kg/day. Vol. 1 No. 2 (2012) ISSN: X (Print); (Online) 2012 DAMA International. All rights reserved. 36

4 Dabhol: Total 14 species of gastropoda were reported from Dhabhol study area. Planaxis sulcatus were abundant i.e.110/m 2, 115/m 2, 122/m 2 in monsoon, winter and summer followed by Babylonia spirata (80/m 2, 86/m 2, 89/m 2 in monsoon, winter and summer respectively). Natica picta (70/m 2, 78/m 2, 70/m 2 in monsoon, winter and summer respectively). Gyrenium natator (60/m 2, 68/m 2, 78/m 2 in monsoon, winter and summer respectively. Followings are the gastropod species are reported as per decreasing order concerned to population density.littorina littorina (45/m 2, 50/m 2, 58/m 2 in monsoon, winter and summer respectively). Thias rudolphi (38/m 2, 30/m 2, 40/m 2 in monsoon, winter and summer respectively). Nerita polita (25/m 2, 28/m 2, 32/m 2 in monsoon, winter and summer respectively). Cellana rata (18/m 2, 25/m 2, 31/m 2 in monsoon, winter and summer respectively). Nassarius thersites (12/m 2, 18/m 2, 23/m 2 in monsoon, winter and summer respectively). Rest of gastropod species found in Dabhol study area were not consistently occurred so they are not considered. Table 3. Study Area: Dabhol Sr. No. Name of Species Seasonal data of population density (Number/m 2 ) 1 Planaxix sulcatus Babylonia spriata Natica picta Gayrenium natator Littorina littorina Thias rudolphi Nerita polita Cellana rata Nassarius thersites Saccostrea Crossostrea Perna viridis Loligo duvacelli Kg/day 1 ton/day 14 Sepia Kg/day Concerned to bivalva: Saccostrea was found to 120/m 2, 132/m 2, 137/m 2 in monsoon, winter and summer respectively. Crossostrea reported 80/m 2, 89/m 2, 93/m 2 in monsoon, winter and summer respectively. Perna viridis found to 55/m 2, 60/m 2, 67/m 2 in monsoon, winter and summer season respectively. Concerned to cephalopods: Loligo duvacelli was found an average 800 kg/day in winter while 1 ton/day in summer season where as sepia was reported only in summer season i.e. an average 600 kg/day. Overall study of population density in selected study area showed that in Harne varieties of mollusc were found, followed by Burondi and Dabhol. Population Density of gastropoda, bivalve and cephalopoda was found to maximum in Burondi followed by Harne and Dabhol. In Burondi, coastline is less as compare to Harne and Dabhol but there is no any human activity, fishing activity and pollution due to which there may be maximum population density of studied mollusc, while in the Harne region various fishing activities are going on which may disturb molluscan habitat whereas Dabhol study area having Ratnagiri Power house might be impacted population density in this region. The present study on density of mollusc shows that intertidal area in Konkan region has a good potential of molluscan population. In general rich density was found in all study areas during winter and summer season. These results are in agreement with many other investigators who have also shown increasing trends of density from monsoon to afterwards (Jaiswar et.al 2006; Parulekar 1973; Harkantara1975, Sreerammurthy 1980, Varshney, 1982, Anni 1989, Chhapagar 1991, Ansari 1979) further these researchers are also reported that population density decreased in monsoon. Mehta (1994) has also reported that decline in population density of Polychaetes in monsoon season, might be due to low salinity by inflow of rainwater. Population density decrease in monsoon season can correlated to environmental factors, wave action, low salinity, ph which is impacting on growth of benthos (Anni,1989). Decreased in salinity up to 15% showed by many workers in monsoon season throughout west coast of Maharashtra (Takur, 1992; Katkar, 1995). Therefore low salinity in studied (mid-west) coast of Maharashtra might be responsible for decreased population density during monsoon season. Abundance of nutrients resulting formation of algal films favours growth of mollusc. Abundance of organic matter in the substratum is reported to be instrumental in determine clam bed (Parulekar, 1973; Sawan 1953). Vol. 1 No. 2 (2012) ISSN: X (Print); (Online) 2012 DAMA International. All rights reserved. 37

5 Bivalve recorded at different site are filter feeder, feeding on phytoplankton and noticeable amount of plankton have been reported in shore water of Burondi followed by Harne, such abundance of plankton would be supporting bivalve population in winter season of studies west coastal area. Population density was found varies in different study area. Since Harne, Burondi and Dabhol are more or less geographically separated receiving different quantity of pollution their ecology must not be similar which has led to adaptation of different species of mollusc and even if similar species are adapted on different shows their growth and other behaviour will not be same (Sparre et.al, 1989, Lecren, 1951). Acharya and Bhattacharya,1983 have reported that variation in the ecological condition of the two habitats or variation in the physiology of the animal or both are responsible for variation in growth rate of the same species from different localities. REFERENCES Acharya P and Bhattacharya D. (1983). Anote on the length-weight relationship and ponderal index of Upeneus sulphurens of Mumbai coast. Geobios. 2: Annie M. (1989). Marine Benthos of the creek and coastal environment of Mumbai Ph. D thesis, University of Mumbai, India. Ansari Z. A. (1979). Macrobenthos of Cochin Backwaters, Mahasagar. 13: Chhapgar B.F.(1991). Sea shore life of India. (World wide fund for nature, oxford university press India) pp. 55. Harkantara S. N. (1975). Benthos of Kali estuary Karwar. Mahasagar. 8 (1 2 ): Lecern C. D. (1951). Length-weight relationship and seasonal cycle in gonad weight and condition factor in perch (Perca fluviatalis). J. Animal Eco. 20: Mehta P. (1994). Bioecology of benthic organisms with reference to changing environment. Ph.D. Thesis, University of Mumbai, India. Parulekar A. H. (1973). Studies on Intertidal ecology of Anjidiv, Island. Proc. Indian Nat. Sci. Acad. 39 (B): Sparee P., Ursin E. and Venema S. C. (1989). Introduction to tropical fish stock Assessment, part 1 manual. Food and Agricultural organization, Rome Sreeramamurthy K. B. (1980). Ecology of intertidal macro fauna at Versova and seven Bunglow beaches, Mumbai, M. Sc. Thesis, University of Mumbai, India. Swan E.F. (1953). IV annual conference on clam research (U.S. fish on wild life service, Boothbay Herb, Marine) 43. Varshney P. K. (1982). Biological productivity of polluted and unpolluted environment of Mumbai with special reference to benthos, Ph. D. thesis, university of Mumbai. Jaiswar A. K., Kulkarni B. G. and Chakraborty S. K. (2006). Population density and biomass of intertidal mollusc along the coast of Mumbai (Bombay), India. Pollut. Res. 25 (1): Thakur M. K. (1992). Studies on eco physiology of some intertidal gastropod of Bombay coast. M. Sc. Thesis, University of Bombay, India. Katkar A. (1995). Hydrobiological studies of selected sites of Bombay, M. Sc. Thesis, University of Bombay, India. Subba Rao N. V., 1991, Mollusca, Animal Resources of India, Vol. 1 No. 2 (2012) ISSN: X (Print); (Online) 2012 DAMA International. All rights reserved. 38