Sustainable natural resources management
FISHERY CATCH STRUCTURE OF KODUNGALURAZHIKODE ESTUARY AND ITS SUSTAINABLE MANAGEMENT V.F. Sanu, P.R. Jayachandran, O.K. Sreedevi & S. Bijoy Nandan Department of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Cochin 682016 Email:
[email protected] ABSTRACT An inimitable feature of the Kerala state is the occurrence of 30 interconnected backwaters (Kayals) having an area of about 38,828ha. The interconnected backwaters support high biodiversity and rich commercial fish and shellfish fauna. These backwaters are internationally renowned for their aesthetic and scientific values including being a repository for several species of fish and shell fishes. This paper describes the fishery catch structure of KodungalurAzhikode estuary during July to December 2009.The average fish production was 1,047 tones. The major fish species recorded were Mugil cephalus, Etroplus suratensis, Ambassis commersonii, Mystus oculatus, Penaeus monodon, Macrobrachium rosenbergii etc. Etroplus suratensis, Fenneropenaeus indicus and Metapenaeus Monoceros 8.35%, 1.91%and 2.19% of the catch respectively. Cichilids contributed 18.48% of the total fish production. The major gears contributed were gillnets, cast nets, stake nets, scoop nets, ring nets, traps and Chinese dip nets. Gill nets contributed 50% of the total fish catch employed for fishing in the estuary exhibited the highest CPUE value (10.8 kg/unit/ hour). The decline in fishery catch and diversity of various stocks has been alarmingly high in the Kodungalur-Azhikode backwater, thus affecting the substance of the fishermen. Many of the species has reached a stage of extinction due to several stress and anthropogenic interventions and modifications, that too particularly the native traditional resources. Key words: Fishery potential, Fishery catch structure, Catch per unit effort, fishing effort INTRODUCTION Backwaters are preferred habitats for about 200 resident or migratory fish and shell fish species and form the crux of the 62500 ha backwater fishery resources in the state of Kerala. (Anon, 2005) Moreover, the interdependence of the adjoining marine and the estuarine zones in completion of the life cycle processes of innumerable aquatic species is amply described in fishery literature (Jhingran 1988; Kurup and Samuel 1987). Kodungalur-Azhikode estuary is a massive and vibrant coastal wetland that contributes a major share of the total area of backwaters (kayals) in Kerala state. More than 20,000 fishermen are directly dependent on the aquatic resources of the estuary 223
Green Path to Sustainability - Prospects and Challenges (2010) fetching over 4000 tons of fish and shell fish annually. Its fishery wealth comprised of over 120 species, including the prized varieties such as the pearl spot, mullets, and the penaeid prawns. The fish and shellfish landed from backwater are valued at over Rs.50 lakhs annually (Anon 2001). Human activities have brought about major changes in the backwater ecosystems and consequently there has been a steady decline in biodiversity of species leading to adverse effect on the fish health. A perfect understanding of the ichthyofaunal diversity of an estuarine system is an essential prerequisite for successful implementation of fisheries development, sustainable utilisation of fishery resources and for adopting suitable conservation measures. The Vembanad backwater has been extensively studied on the composition, distribution and gear wise catch of major fishery (Shetty 1965, Anon 2001, Bijoy Nandan 2007, Bijoy Nandan 2008). Of late due to various human induced activities, there have reports on the decline in the catch of fishery from the coastal estuaries particularly the Kodungalur-Azhikode estuary (Anon 2001; Anon 2005; Bijoy Nandan 2008). Therefore, this paper discusses the diversity of fishery, the gear wise yield and Catch Per Unit Effort (CPUE) in the Kodungalur-Azhikode estuary. The Kodungalur-Azhikode backwater which is an extension of the Vembanad backwaters in northern region is also an ideal habitat for several species fish and shellfish (Anon 2001). MATERIALS AND METHODS Kodungalur - Azhikode estuary lying in the northern end of the Ernakulum district (Lat 10o 10’ N, Long 760 15’ E) has an approximate area of 696 ha. The southern branches of the Karuvannur River and Chalakkudy River empty in to this backwater system. The data on fish catch composition, gear wise catch, weight of each species, were collected from selected landing centers in Kodungalur-Azhikode backwater on a weekly basis from July to December 2009. Anapuzha and Krishnankotta were the major fish landing centers in the estuary. The fish catch composition, gear wise catch (Kg/unit) yield per hector of each of the fish stocks were collected based on landing centre based approach (FAO 1965, Guptha et al 1997). Based on this method, the catches obtained on a weekly basis are summed up to get the monthly data. Normally fishing days in this area are up to 20 days. So, the monthly data obtained are converted for the period of fishing data and then summed up to get the seasonal /annual catch / fish landings in the backwater. The details on the gears, the fishermen and the price structure of commercially important fishery were also collected from the backwater during the period of study. The fishery data was subjected to multivariate analysis using the PRIMER Version 6.1 (Plymouth Routines Multivariate Ecological Research) software. The various diversity indices viz Shanon- Wiener diversity index (H’), Species richness- Margalef index (d), Evenness index- Pielou’s evenness index (1966) and Species dominance-Simpson’s index (Lambda) were analyzed using the PRIMER software The Catch per Unit Effort (CPUE) is expressed as Kg/unit/hour was computed for the monthly and annual values and used as index of relative abundance (Guptha et al., 1997). The information on the number of fishermen, fishing hours, price structure of different species was also collected. The yield obtained for each of the fishery, was converted to percentage abundance for interpretation on gear wise composition and distribution of different species in the estuary. The species wise identification of fishery was done based on standard works (Day 1958; Talwar and Jhingran 1988; Munro 2000) and also Fish Base (www.fishbase.org). 224
Sustainable natural resources management RESULTS AND DISCUSSION Fishery catch structure During the study period, twenty five species of fishes six species of shellfishes, one species of crab and one species of clam were identified that contributed to the fishery of KodungalurAzhikode backwaters. Of the thirty three species, fourteen have been recorded from the estuarine region whereas four were predominantly from rivers, that take a sojourn to the backwater during the monsoon when salinity remained very low in the upper reaches, and they were Labeo rohita, Catla catla, Mystus oculatus, and Oreochromis mossambicus. Purely marine forms were also recorded from the backwater and contributed 5.4% of the total fish catch in the estuary, represented by Acanthopagrus berda, Cynoglossus sp., Leiognathus splendens, Ophichthys altipinnis and Psettodus erumeii.(Table 1) These marine species dominated the catch during Nov-Dec period of the estuary. The major groups / species constituting to the fishery with their relative contribution are given in figure 1. Etroplus suratensis, Fenneropenaeus indicus and Metapenaeus monoceros contributed to the fishery of the backwater 8.38%, 1.91%, and 2.19% respectively. The grey mullet formed a share of 11.45% of the total catch. Etroplus maculates (4.28%), Ambassis commersoni (4.02%), Cichilids contributed 18.48% of the total fish production. Parupenaeus indicus (2.06%), Lates calcarifer (1.3%), Scathopagus argus (5.92%) and Mystus oculatus (9.63%) also formed commercially important species in the fishery of the estuary. Among shrimps, the Metapenaeus dobsonii, contributed 9.65% to the total landings. The giant freshwater prawn Macrobrachium rosenbergii contributed 0.46% of the total fish landings. Metapenaeus monoceros formed a share of 2.19% followed by P.monodon with 2.32%. The black clam Villoritta cyprinoids contributed 1.4% of the total landings. The Crabs also formed a very attractive fishery with a share of 38.59 tons. The annual catch of fish and shell fishes in the present study was 1046 tons in the KodungalurAzhikode back water. During the first half of the study (July-September) the catch was 462.712 tons which increased to 584 tons during the second half (October to December).The yield per hector was 1503.77 Kg. Studies by Central Inland Fishery research institute (CIFRI) reported a total catch of 2747 tons in the same estuary during Anon (2001). When the present catch of fish and shell fish was compared with that of the studies by CIFRI, it showed a gradual decline in the catch. During the period of 1998-99, 60 species of fishes, 6 species of prawns and 1 species of crab formed the fishery of Kodungalur-Azhikode backwater (Anon 2001). In the present study during July – December 2009 recorded 25 species of fishes, 6 species of prawns and 1 species of crab were recorded. Fishes contributed a share of 22.77% (366.14 t), that of prawns by 77.22% (1241.3 t) and crab by 3.08% (49.61 t).During the present study, fishes contributed 80.63% (843.88t), that by prawns 14.29% (149.59t) and crab 3.68% (38.59t). Etroplus suratensis, Penaeus indicus and the Metapenaeus monoceros represented 2.11%, 8.62 %, and 7.25% in the total catch (Anon 2005). The grey mullet contributed 2.69%. Etroplus maculates (0.24%), Ambassis commersonii (0.73%), the cichlids contributed about 20% of the total production. Lates calcarifer (0.41%), Scathopagus argus (0.03%), and Mystus oculatus (0.7%) also formed a commercially important species in the fishery. Among prawns, the most significant contributor to the fishery by bulk was the Metapenaeus dobsonii, contributing to the tune of 50% to the total landings. Fish catch by seine net were reported from earlier studies by Anon (2001). However, fishing using such nets could be observed during the present investigation. The Shannon diversity index (H’ log2) was (4.4746) that of Margalef richness index (d) was (2,4167) that of Pielou’s evenness index (j’) was (0.88705) the diversity richness, eveness indices of the 225
Green Path to Sustainability - Prospects and Challenges (2010) fishery in the back water were quit high indicating that the abundance of the different species quite encouraging. Gear wise distribution Most widely used gillnets in this study area were ‘Disco net’ and ‘Vyshalivala’ which could be unfriendly fishing gears due to its small mesh size (18 mm). Among this, disco net was most widely used. Disco net is used for surface, midwater and bottom fish catching purpose. Cast nets known as ‘Veesuvala’ are well adapted for the capture of small shoaling fishes. Chinese dip net, contributed 14% of total catch (150 tones). About 225 Chinese dip nets were deployed in the Kodungalur- Azhikode backwater, and is given in figure 2. Stake nets are conical bag nets set against current with the help of poles erected to the bottom. About 280 stake nets were present in the study area and shown in Table 4. A comparative study of the distribution of various gears in Kodungalur-Azhikode backwater with previous reports (Anon 2001) revealed that gill nets decreased from 360 to 260, stake net from 445 to 280 and Chinese dip nets 246 to 225. New operational gears such as scoop nets, traps and ring nets were also observed in the study area. Such gears were not reported from the earlier reports by Anon (2001). Catch per unit effort (CPUE) The different gears used for fishing in the estuary were, gill nets, stake nets, cast nets, scoop nets, traps, ring nets and Chinese dip nets. Gill nets contributed a share of 525.43 tons (50%) of the catch during the present study followed by stake nets 95.8t (16.96%), Chinese dip nets 14982t (14.31%), cast nets 177.46t (9.15%), scoop nets 35.44t (3.39%), ring nets 33.38t (3.19%) and traps 31.4t (3%) (Table3). Catch per unit effort for various gears reported from earlier study by Anon (2001) ranged from stack nets 6.3 kg/unit/hour to lowest 3.1kg/unit/hour for gill net. The CPUE values were considerably higher for various gears as compared to the previous study from the same estuary by Anon (2001). This indicated that fishing effort as well as fishing intensity has increased during the present study as compared to the previous report. However the diversity & the catch of fishery as shown sigh of decline in the Kodungalur-Azhikode Back water. Fishermen population and income distribution The study was restricted to the enumeration of active fishermen whose primary job was fishing in backwaters. The disposal of the landings brought ashore by the fishermen was, in general, through auction at the landing sites. Though majority of the fishermen was organized into societies, the societies seldom responded to the monetary needs of the fishermen through arranging fair price sale. At the auction site, the vendors dictated the prices and often the fishermen were forced to sell the catch at poor prices having no other option to the landing sites. Agents of the processing companies were ubiquitously present at all major landing centers for the purchase of the higher priced prawn and crab species. These items received more or less steady price depending on the count of the harvested prawn. Study carried out to estimate the economical value and production potential of commercially important species of fin fishes and shellfishes in Kodungalur- Azhikode backwater were given in figure 4. Among fin fishes, Valamugil fetches more price rated as Rs. 250/ Kg, but its production is found to be low about 69.5 Kg/ha, were as Mugil cephalus fetches Rs.150/Kg, its production was found to be about 172.5 Kg/ha. Among shellfishes, Penaeus monodon fetched more price than other prawns rated at Rs. 435/ Kg and its production was found to be low about 7.5Kg/ha. Market value of Scylla sp. and Villoritta sp. were found to be Rs. 250 and Rs.60/Kg respectively. (Fig.4) 226
Sustainable natural resources management The disposal of the landings brought ashore by the fishermen was, in general, through auction at the landing sites. Majority of the fishermen was organized in to societies, the societies seldom responded to the monitory needs of the fishermen through arranging fair price of sale. At the auction site, the vendors dictated the price of the prized fishes like mullets, pearl spot etc. and often the fishermen were forced to sell the catch at poor prices having no other option but sell of this catch in the landing sites itself. An estimation of the price share indicated that on an average, fishermen received only 50-75% of the market price at the landing sites through auction. CONCLUSIONS The fishing effort should not be allowed to increase further and has to be restricted at least to the current level until further recommendations are made based on further studies on population dynamics on major fish/shellfish species of the estuary. There is an urgent need to restrict the mesh size of the stake net, Chinese dip net and gill net to ensure that sufficient fish reach the adult size classes. Though minimum mesh size of 25 mm (stretched) is advisable, considering that M.dobsonii is also to be exploited, the minimum mesh size maybe restricted to 18mm. Several of the stake nets are being employed during the tide incursion to the backwaters against the norms. The enforcement machinery should be strengthened to ensure that the stake nets are deployed only during the receding phase. A considerable area of the backwater has already been lost to reclamation for agricultural, mining, urban area development and similar activities. Further encroachment/ reclamation should be regulated. REFERENCES Abdul Azis, P.K. and Nair, N.B. 1987. The estuarine of Kerala with reference to the status of aquaculture development. Proceedings of the National Seminar on Estuarine Management, 4-5 June, 1987, Trivandrum, pp.532-541. Anon, 2001. Ecology and Fisheries Investigation in Vembanad Lake, CIFRI Bull.No.107, ISSN 0970616 X,P.38 Anon, 2005. Fisheries and Environment Assessment in selected backwaters on the south west coast of India CIFRI (ICAR),Bulletin No. 139:44. Anon. 1961-1962. Central Inland Fisheries Research Institute Annual Report, 55pp. Bijoy Nandan, 1991. Effect of coconut husk retting on the water quality and biota of an aquatic biotope in Kerala. Ph.D. Thesis. University of Kerala. Bijoy Nandan. S 2008 Abundance and diversity of biotic resources in selected wetlands on the south west coast of India In: Glimpses of Aquatic Biodiversity, Special Publication No: 7, ISBN : 978-81-907269-6-2, 252-269p. Bijoy Nandan. S and Unnithan, V.K. 2007. Ecology of Vembanad lake with investigations in Vembanad lake, CIFRI (ICAR), Govt. of India, Bulletin No. 107: 38P. Bijoy Nandan, S. 2005. Ecology and biodiversity of Kayamkulam lake. Bulletin no FW-A-8, CIFRI publication, P 33-38 Bijoy Nandan, S 2004. Studies on the impact of retting on Aquatic Ecosystems, ISBN 81-9019390-2, Limnological Association of Kerala, India,120 p. DAY, F. 1865. The Fishes of Malabar, London. DAY. F. 1878. The fishes of India, Vol.1. William Dawson and sons Ltd., London, pp. xx + 778 227
Green Path to Sustainability - Prospects and Challenges (2010) DAY. F. 1889. The fauna of British India including Ceylon and Burma. Fishes Vols (1&2) 548 pp and 609 pp. De Bruin, G.H.P., Russell, B.C. and Bogusch, A. 1995. FAO species identification field guide for fishery purposes. The marine fishery resources of Sri Lanka., Rome, FAO. 400p. Gopinathan, K. 1985. Ecology and fisheries of certain inland water bodies of Kerala Ph.D. Thesis, University of Kerala. Gupta, R.A., Mandal, S.K. and Paul, S. 1997. Methods of collection of Inland Fisheries Statistics in India Part- 1, survey methodology guidelines Bulletin No.77, CIFRI Publication. P.64 Hart, P.J.B. and Reynolds, J.D. 2002. Handbook of fish biology and fisheries, I. (Blackwell Science Ltd. U.K.) 101-102p. Hilborn, R. and Walters, C.J. 1992. Quantitative Fisheries Stock Assessment: Choice dynamics and uncertainty. Chapman and Hall, New York. Hora, S.L. 1951. Fresh water fauna. Handbook of Indian fishes, 4: 34-39 Hora, S.L. 1955. Fish geography of India. J. Zool. Soc. India., 3(1):183-187. Gulland. J.A. 1965. Manual of Methods for fish stock assessment.Part 1, population analysis. Technical paper no 40. Revision 1. Jhingran, A.G.1988. Fish and Fisheries of India Revised and Enlarged Second Edition, Hindusthan Publishing Corporation, Delhi. John, C. 1958. A preliminary study of the Kayakulam lake. Bull. Central Res. Inst. University of Kerala, Trivandrum, 7(1): 97-116. John, C.C. 1948. Progress Report of the Fisheries Development Scheme. Central Research Institute, Travancore University, Trivandrum. Kurian. C.V., Damodaran R. and Antony A. 1975. Bull. Dept. Mar. Sci. Univ. Cochin, 787p Kurup, B.M. and C.T. Samuel, 1987. Ecology and fish distribution pattern of a tropical estuary. Proceedings of the National Seminar on Estuarine Management, 4-5 June 1987, Trivandrum, Nair N.B. ( Ed.), pp. 339-349. Kurup, B.M. and C.T. Samuel. 1985. Fish and fishery resources of the Vembanad lake. Proc.Symp. Harvest and Post Harvest. Tech. Fish., 77-82 Kuttayamma.V.J. 1980. Studies on the prawns and the prawn larvae of the Kayamkulam lake and the Cochin backwaters. Bull. Dept. Mar. Sci. Univ. Cochin, XI : 1-38. Munro, 2000. The marine and freshwater fishes of Ceylon.Narendra publishing house, Delhi ISBN 81-85375-06-2 Nelson. J.S. 2006. Fishes of the world 4 th edition. John Wiley & sons U.K. 624 pp Nelson, J.S. 1994. Fishes of the world 3rd edition. John Wiley and Sons.Inc., N.Y., 600 pp. Nikolsky, G.V. 1980. Theory of fish population dynamics (Translated by J. E. S. Bradely). Jones, R. (ed), Bishan Singh Mahendrapal Singh, Dehradun and otto Koelts, science publishers, Koeltz. Science publishers, Koeminstein, Germany. 359 pp. Nikolsky, G.V.1963. Ecology of fishes. Academic Press, London, 352 pp. 228
Sustainable natural resources management Pauly, D. 1984.Fish population dynamics in tropical waters: a manual for use with programmable calculators. ICLARM Stud.Rev.8: 325 p. Shetty H.P.C. 1965.Observations on the fish and fisheries of the Vembanad backwaters, Ke rala. Proc.Natn.Acad.Sci. India, 35:115 Talwar, P.K. and Jhingran A.G. 1991 Inland fisheries,vol 1&2 Oxford & IBH Publishing Co. Pvt. Ltd. Unnithan, Bijoy Nandan and Vava., 2005 Fisheries and environment assessment in selected backwaters on the South West coast of Kerala. Bulletin no 139, CIFRI Publication, 26-34 Unnithan, V.K. and Bijoy Nandan. S. 1999. Ecology and fisheries with special reference to Macrobrachium rosenbergii, In: Advances in Biology, Aquaculture and Marketing, Proc. International Symposium on Freshwater prawns, Part II, P: 748-753, ISBN: 81-8424-166-6.
Figure1. Mean percentage abundance of fishery resources in the Kodungalur-Azhikode backwater
Figure 2. Distribution of major gears in KodungalurAzhikode backwaters
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Green Path to Sustainability - Prospects and Challenges (2010) Table 1. Relative abundance and habitat of the finishes contributing to the fishery of KodungalurAzhikode backwater. (July-December 2009)
Table 2 Relative abundance and habitat of the Shellfishes contributing to the Kodungalur- Azhikode backwaters
***** Abundant **** Moderate *** Frequent ** Rare * Occasional E- estuary M- marine F- freshwater
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fishery of
Sustainable natural resources management Table 3. Average CPUE and percentage contribution by different gear to the landings in Kodungalur-Azhikode backwater (July- December 2009)
Figure 3. CPUE values of different gears used in Kodungalur- Azhikode backwater
Figure 4. Value and yield per hector of fishery in KodungalurAzhikode backwater.
Table 4. Composition of fishing gears and period of operation
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