REPORT ON MONITORING OF ECOLOGICAL HEALTH OF THE MEKONG RIVER

Transcription

1 Mekong River Commission REPORT ON MONITORING OF ECOLOGICAL HEALTH OF THE MEKONG RIVER by Lieng Sopha Inland Fisheries Research and Development Institute (IFReDI) Department of Fisheries, Phnom Penh, Cambodia Contract No. PP Period: March-December 2003

2 INTRODUCTION Besides rice, fishes are important to mankind as a vital source of protein and cash income for many of the poor in the Mekong River Basin. Fish is a highest trophic level of aquatic animal and main resources in the Mekong River System. In the Mekong, fish are the major protein consumed more than other meats such as poultry, pork, and beef. Fish is a traditional product such as fish paste, and smoked fish are an invaluable source of calcium, vitamin A, and other nutrients. Fish is easier to digest and still comparatively cheap, the poor can afford to buy and can find almost everywhere. Fish is not only a source of vital protein to the population, it also provides employment for the rural people, gaining some of foreign exchange and creating opportunity for recreation such as ornamental and sport fishes. In 2003, the annual catch in the whole Lower Mekong Basin, Cambodia, Lao PDR, Thailand, and Vietnam is estimated 1.5 millions tones, with another 500,000 tons raised in reservoir an other forms of aquaculture. The annual value of the capture fishery is an estimated USD 1,042 million, aquaculture an estimated USD 273 million and the reservoir fishery an estimated USD 163 million, excluding the considerable earnings from trading and processing (MRC report, 2003). The fishery of the Mekong is very important for the 55 million people who live in the Lower Mekong Basin. An estimated 40 million rural dwellers are involved in fishery at part-time or seasonally. In Lao PDR, for instance 71 percent of rural households depend on fishery to varying degrees. In Cambodia, more than 1.2 million of 11 million Cambodian people who live in fishing communes around the Tonle Sap Lake depend almost entirely on fishing for their livelihood. The fishery is vital important for their nutrition, food security and income. Although there is a report that the status of the Mekong River is still relatively healthy, but there is a number of threats to the Mekong fishery. The changes of the volume of flow, timing and duration of the Mekong flood caused by the dams and weirs built for hydropower, erosion and sedimentation, irrigation and flood control are constructed not in the way safe for the health of the river and have increased concern the impact on fish habitat and aquatic resources in the Mekong as whole. Therefore, the monitoring system to investigate the status of the Mekong River must be established as soon as possible, so that measures could be taken on time to maintain the health and the resources of the Mekong River, the vital source of livelihood of the Mekong people. Among the aquatic animal in the basin, fish is the highest trophic level. Monitoring of the status and trend of fish and the fisheries indicate the final consequences from all human activities that people are interested to know. Therefore, the monitoring of fish and fisheries are initiated to be set up as an indication of ecological health of the Mekong River, and the status of fish as food and income of the rural poor. The trial fish survey was conducted at 11 sites from Nam Ou, Lao PDR, down to Ubon Ratchathani, Thailand and to Cambodia from middle of May to early June The objectives of the survey is to test and formulate a comprehensive fish biological monitoring method, which can be applicable to the whole Mekong River, where there is different water regime, aquatic resource and ecological characteristics at each section of the River. 2

3 METHODS DATA COLLECTION Fish sample were taken from gillnets of multiple mesh sizes (2.5, 3.5, 4.5, 6.5, 8 and 10 cm) with length of 80 m and 2 meters depth. The gillnets were set along riverbank at both left and right sides according to the condition of riverbanks. Two fishers were hired to set nets at each sampling site. The nets were set in the morning (9-10AM) and taken out in the afternoon (15-16 PM). The nets were soaked in water for about 5-6 hours per day. All relevant information, such as time of setting and taking out the net, size and mesh size of gill nets were filled on species composition data sheets (Appendix I). As soon as the fish catch were released from nets, they were sorted out by species. The fish were identified to species level at the field. All fish catch were identified, weighed individually and entirely, and counted total number of fishes. Fish sample were identified based on Fishes of the Cambodian Mekong guidebook (Rainboth, 1996), the fishes of Laos, and other reference documents available. The information on the species, and weight were recorded on data sheets of species composition. Data for condition factor was also collected for the survey. Species which are abundant such as Hennicorhyncus siamensis, Cyclocheilichthys enoplos and Sikukia sudgeri were measured their total length in milimetres and weighed individually at the precision of grams (Appendix II). This data were taken from fishes from fishermen fishing around the sampling sites. All this fish data was sampled from the following sites: Table 1. Sampling Sites and Dates: Sites No Dates Sampling locations Countries Codes 1 24/05/03 Pak Nam Ou Lao PDR LPN 2 25/05/03 Nam Ou Lao PDR LNO 3 23/05/03 Luang Prabang Lao PDR LPB 4 27/05/03 Vientiane Lao PDR LVT 5 29/05/03 Pakse Lao PDR LPS 6 31/05/03 Ubon 1 Thailand TM1 7 01/06/03 Ubon 2 Thailand TM2 8 02/06/03 Ubon 3 Thailand TM3 9 07/06/03 Upper Mekong Cambodia CUP 10 06/06/03 Phnom Penh Port Cambodia CPP 11 05/06/03 Koh Khel, Bassac River Cambodia CBS DATA ANALYSIS The collected was processed using descriptive statistics. The condition factors were analyzed for 5 species: Cyclocheilichthys enoplos, Barbodes gonionotus, Cyclocheilichthys lagleri, Henicorhynchus siamensis and Dangila sp. Cf. cuvieri are studied by using all length and weight data collected in the survey from 19 May to 7 June 2003 at the sampling sites: Luang Prabang, Nam Ou,Vientiane and Pakse, Lao PDR, Phnom Penh port and Phnom Penh upper Mekong, Cambodia. The condition factor q i is calculated for individual fish of known-length and weight, when the general length-weight equation is determined for each species. The length-weight relationship 3

4 was established by calculating the least squares fit through the data points of each species using the equation y = qx b, where q and b are constants, y the weight and x the total length. This length-weight equation is given for each species in the chart with the data points (Dirk, 2001). A mean weight-based condition factor (CF w ) can be calculated from this: CF w = (mean weight).(predicted mean weight) -1 To define the condition factor, we need to define the relationship between fish length and weight for the selected species. It is universal that the growth of fish or any other animal increases with influence in body length. Length and growth of a species are interrelated (Biswas, 1993). The formula describing the relationship between fish length and weight are: W = a L b (Huxley 1924). Where W stand for weight, L for length, a is constant and b the exponent. In isometrically growing fish, the exponent in the power equation describing the relation between the length of a fish and its weight is "3". The equation W = al 3 describe the relation between length and the weight. In case of allometry, the exponent b in the more general power of the equation b will be differ from "3". In these equations, a is a constant to be determined empirically. RESULTS SPECIES DIVERSITY There is 59 species encountered the catch monitoring survey (Appendix III). The frequency of species occurrence varied between sites. Ubon Ratchatthani sites TM2 (22 species) and TM3 (12 species) have the most number of fish species and Pakse, Lao PDR 11 species. There is commonly around 5-12 species encountered at each site. The number of species is likely to increase downstream, although Ubon Ratchathani site 2 and site 3 got the highest frequency of species occurrence (Fig.1). All 59 species represent 14 families. The family Cyprinidae has the most number of fish species (30 species) and followed by Panagasidae, Mastacembelidae, and Bagridae. Most of the families consists of a few species occur in the survey (Fig. 2). 4

5 Figure 1. Frequency of Species Occurrence at each Site LPN LNO LPB LVT LPS TM1 TM2 TM3 CUP CPP CBS Upstream N = 94 Downstream Number of Species Figure 2. Species Occurrence by Family Notopteridae Nandidae Helostomatidae Engraulidae Eleotridae Channidae Chachiridae Siluridae Cobitidae Pangasiidae Mastacembelidae Bagridae Cyprinidae N = Number of Species All 59 species were observed occurring in 5 communities based on their frequency of occurrence. Paralaubica riveroi (Par. ri) uniquely occurred separately. It has no association with any other species. The large community consists of 48 species. They are associated in the large community, which is composed of many sub-communities. The other three communities resemble in a group of 2-4 species (Fig. 3). 5

6 Fig. 3. Clustering of 59 species Par. ri. Pun. gon. Thy. thyn. Ost. mel. Mys. nem. Bot. mod. Bot. eos Bot. hel. Bot. lec. Lei. sia. Mac. am. Mys. am. Rai gut. Kry. chev. Cir. mic. Hel. waa. Bar. schw. Lob. mel. Ham. macr. Hel. tem. Not. not. Oxy. mar. Ach. leu. bar. alt. Het. boc. Lob. quad. Mast. arm. pro. jul. Amb. tru. Mor. chr. mac. tae. Nan. nan. Ery Mek. Pan. ple. Cha. str. Hen. sia. Kry. apo. Pan. con. Por. dea. Sik. ste. Cyc. lag. Dan. ku. Lep. hoe. Lyc. cro. Pan. sia. Mys. wol. Mac. sia. macr. sp. P. hyp. Pacu. par. typ. Hen. sp. Sca. ban. Cyc. en. Pun. pro. Dan. cuv. Sik gud. bar. gon. Ost. has. DISTRIBUTION Most species occurred at one site and only small number of species was found occurring at more than 2 sites. Around 7 to 8 species arise at a few sites, and only a few species appear at more than 3 sites (Fig. 4). The site at Phnom Penh port, Cambodia has characteristics different from the other sites. Although site 1 at Mun River, Thailand, site at Vientiane, Nam Ou, Pak Nam Ou and Luang Prabang, Lao PDR, and site of upper Mekong, Cambodia are in different geographic position, but they are in some ways of similarity of species occurrence. Site at Pakse and site 2 at Mun River is associated with each other. The site at Bassac River and site 3 at Mun River appear distinct from the other sites (Fig. 6). 6

7 Fig. 4. Number of Sites a Species Occurred at 6 Number of Sites, a Specie Occurred at No = Number of Species Fig. 5 Clustering of the 11 sites Dendrogram for the 11 sites LPB LPN CPP CBS TM3 LVT CUP TM1 LNO LPS TM2 7

8 ABUNDANCE All 59 species encountered at all sampling sites, 6 species are comparatively most abundant. All the six are from of the family Cyprinidae such as Dangila sp. Cf. Cuvieri, Sikukia gudgeri, Barbodes gonionotus, Puntioplites protozysron, Osteochilus hasselti and Cyclocheilicchthys enoplos. Barbodes gonionotus, Cyclocheilichthys enoplos, and Puntioplites protozysron are commonly appear throughout the sampling sites. Some 10 species are moderately abundant. The other 27 species are least abundant (Fig. 6 and Appendix III). Fish are comparatively high abundant at site 2 and 3 at Mun River and site at Phnom Penh Port. Fishes are less abundant at other sites. The catch per unit of fishing effort was around Kg (Fig. 7). Fig. 6 Fish Abundance by Species Other Raiamus guttatus Mystus amartus Morulius chrysophekad. Macrognathus amartus Lobocheilos melanotaenia Leiocassis siamensis Kryptopterus cheveyi Henicorhynchus siamensis Cirrhinus microlepis Botia lecontei Botia helodes Botia eos Barbodes schwanefeldi Amblyrhynchich. Trunca. Sikukia stejnegeri Mystus wolffi Botia modesta Thynnichthys thynnoides Osteochilus Helicophagus waandersi Mystus nemurus Pacu (alien species) Scaphognatops Bandan. Paralaubica typus Paralaubuca rivreoi Henicorhynchus sp. Cyclocheilichthys enoplos Puntioplites protozysron Osteochilus hasselti Barbodes gonionotus Sikukia gudgeri Dangila sp. Cf. cuvieri N = Abundance (No of fish) 8

9 Fig. 7. Abundance by Site (Kg per 1000 sq. m of Gill Net) Site LPN LNO LPB LVT LPS TM1 TM2 TM3 CUP CPP CBS Fish Catch (Kg) per Unit of Fishing Effort CONDITION FACTOR The value for indicating condition of fish living in the habitat at the sampling sites in a section of the Mekong River is shown in Table 2 below for a number of selected species. Table 2. Condition Factors (CF) for Cyclocheilichthys enoplos, Barbodes gonionotus, Cyclocheilichthys lagleri, Henicorhynchus siamensis and Dangila sp. Cf. Cuvieri Scientific names Sites LPB LNO LVT LPS CPP CUP Cyclocheilichthys enoplos (n=29) Barbodes gonionotus (n=29) (n=13) Cyclocheilichthys lagleri (n=21) Henicorhynchus siamensis (n=6) (n=45) Dangila sp. cf. cuvieri (n=57) (n=11) Remarks: LPB stands for Luang Prabang, LNO= Nam ou, LVT= Vientiane, LPS= Pakse, CPP= Phnom Penh Port, CUP= Phnom Penh Upper Mekong. In the bracket is number of fish sampled. 9

10 DISCUSSIONS Fish species varied between sites in this survey. Fifty-nine species were encountered at all sites. This number of species will be added up, if the sampling effort increases (MRC. 2003). Species diversity survey needs to have the standardized sampling methods. For this study, the gill nets were standardized and used throughout all sampling sites. In addition, the number of species is likely to increase downstream, although Ubon Ratchathani site 2 and site 3 got the highest frequency of species occurrence (Fig. 2), which is confirm with Mark, 1995, Kinsolvin and Bain, 1993 and MRC, Species diversity is useful indicator of the final results from the impact on the ecosystem health. Species is considered as a fundamental biodiversity unit. Often the species as indicator used in environmental monitoring or assessment. This is a reasonable approach since an increase in the number of species will be accompanied by organismal and ecological diversity (MRC. 2003). On the other hand, in response to the stress of the ecosystem, which could be environmental degradation or over fishing, the large individuals and species tend to disappear as stress increases. By keeping a good records of fish species occurrence provide a good history of fish species occurrence served as a basis to investigate what species has been lost from the ecosystem or decline in stock. Some species have a biologically restricted range of habitat, when their specialized habitats are altered, these species are vulnerably threaten. As a consequence of habitat change or disappear, only those fish species with the appropriate adaptations to their physiological and biochemical systems can survive and reproduce in the new environment (Hochachka and Somro, 1984). By monitoring of species occurrence and species diversity will tell a long-term change, which is an indication of impact to the ecosystem. From this measures need to be considered to prevent its deterioration in the future. The abundance and distribution of fishes demonstrate how the Mekong River system's living aquatic resources have intricately adapted to the different condition of life along the system. This abundance indicates the changes of threaten species under the pressure of human activities and natural fluctuations. The abundance of freshwater fish species has been influenced by human activities such as harvesting of plants, sediments regime, characteristics and changes of hydrology. The healthy ecosystem supports organism in habitat where they live. When the ecosystem does not support well then the abundance declines over time. In addition, when the environment of the river change, the life cycle of some fish species has been disrupt, because they are unable to the new environment and then disappear from the system. But some species can adapt to the new environment and their population still remains abundant (Buijse and Densen, 1992). However, at the particular section of river, most individual species attain maximum abundance that provides conditions most suitable for them (MRC, 2003). The changes of fish abundance and diversity are an indicators of the impact of the change of the condition of the river ecosystem. The impact on the health of the river can be by the construction of physical barriers such as canals and roads or even hydrologic barriers creating poor connection between different water bodies. These barriers block migration of many fish and consequences reduce their range of movement causing the decline in abundance and some fish may become extinct. As such, understanding of status of the widespread distribution in the basin and understanding other key factors affecting presence and absence of the species. 10

11 Ecosystems with greater diversity of fish species and within more complex nutritional chains (aquatic biological production systems) ultimately will be the more stable (Karl, 1976). The ecological health of the river, it is as a basis on how the habitat quality and its spatial extent can be improved so that fish abundance and diversity in some ways can be maintained. In addition, the value of the condition factor q i is a measure indicating the condition of fish, supposing that the weight of a fish directly linked to its condition or "well-being" (King, 1995). The more a fish weight at a given length, the greater will be its factor q i and the higher the value of the factor (CF) the faster the growth of fish. Therefore, reflecting the more favorable environment given to organism where they live. The greater the CF values the better the well being of the fish in the environment. On the other hand, the lower the CF value, the worse condition of the environment of the river where the fish live. The condition factors, which were calculated from monthly sample, can allow the detection of the monthly variations in the condition of fish. However, this survey intends to regularly assess the condition of the river at the particular time of the year to monitor status and trend of fish resource, which reflecting the health the river. These variation of condition factor may be related to fluctuations in food availability, reproductive activities of the species, etc. If there is need for further clarification and interpretation, additional information is required. CONCLUSION The indicators, species diversity, fish community, abundance, and distribution are very useful parameters and commonly used to monitor or assess status and trend of fish resources. Furthermore, condition factor also provide important information on the growth performance of fishes and the condition of well-being. Long-term survey for monitoring of the health of the Mekong River should be adopted and use these indicators. The indicators can demonstrate the response of fish to the changes of the environment where they live. Stationary gill net of multiple mesh size is useful sampling technique for fish data collection for monitoring fish resources. It is widely used in fisheries study, and easy to bring from one to other locations. It can be applicable to sample fish in the Mekong River in the dry season. Gill net is widely used by local fishers at everywhere throughout the Mekong River. the fishing methods were also used by other scientists in the past such as rotenone, seining, electro-fishing and trawling, but it concerns with cost, fishing permit, and the rotenone can cause harmful to the environment and the people. RECOMMENDATIONS The survey was conducted so far in May and June To improve the future survey of this ecological health of the Mekong River, based on the primary results and field experiences, some recommendation are made as follow: Selection of a species as indicator for ecological health of the Mekong River health should include endemic species representing some aspect of biodiversity. The species of flagship and perform long distant migration. This is a good indication of how is the condition of fish passage along the Mekong River. 11

12 Fish size distribution is missed recording in this survey. This is also useful biological indicator demonstrating the consequences of impact on the ecosystem. In the biological decline of the fisheries, the fish size composition will be change from large species dominant to small species dominant in the catch. Sampling methods used at site depend very much on condition of the fishing grounds. Therefore, the samplings were in some ways differ from previous plan. Seine net was also planned to use for the sampling. But because of the net was very heavy (about 80 Kg, mesh size 3 cm, 12 m depth, and 120 m long), it was costly to transport between several sampling sites. The seine net was not decided to use. The seine fishing is by sweeping the area, similar to marine trawler, which is frequently used to monitor marine fisheries and also used by a research team from the University of Michigan School of Natural Resources in 1975 in the lower Mekong River. The seine net catch non-selective species and size, the sampling catch can be used to calculate the fish density per unit area of fishing grounds. The density is popularly used to monitor fisheries. Fish catch was extremely low as compared to the catch of local fishers whose nets were set from early morning at 5 AM until 15 0r 16 PM, particularly at Nam Ou, Lao PDR, where the water velocity is fast. Gill nets are not suitable to use at that site and that time. Local fishers mostly used cast net and floating gill nets to fish. The catch from cast net and floating gillnet were higher than stationary gill net in such fast flowing water. Therefore, the net should set in early morning and the sampling should be started in dry season so that the water condition is suitable for setting the nets. To secure the sampling for data collection, it necessary to get fishing permit from local authority to fish in close fishing season. There is some limitation of the technique to define the condition factor of fishes. The factors in the length-weight equations are to estimates of the population parameters based on a limited sample. The sample of fish are not of the same size, given that they consisted of sometimes mainly large fish and at the other time small fish dominates. These make bias of the value of condition factor for comparison. The factor changes between locations, sizes of fish, and on monthly basis. Therefore, this is some points to consider for the future survey. The data should be collected over long-time horizon so that the investigate status and trend of fish resources which reflect the condition of fish habitat, feeding regime and the impact on fish growth and survival in the environment. The data for assessing condition factor can be taken from any gear to fulfilling the need for sufficient data. Time of sampling at each site need to be extended for over a few days, so that it can show clearer picture of the status of fish resource at each site. Fish is fast moving organism has more ability to escape from the nets better than smaller creature and migration activities related to time of the day. 12

13 REFERENCES Bailey, R. G. (1988). Ecographic analysis, a guide to the ecological division of land for resource management. U.S.D.A. Forest Service, Misc. Publ. 1465, Washington D.C. Biswas, S.P Manual of Methods in fish biology. South Asian Publishers Pvt Ltd., New Delhi International book Co, Absecon Highlands, N.J. pp. 60. Buijse, A.D. and W.L.T.V. Densen (1992). Training Manual on Handling for Fish Ecological Studies in Lake and Reservoirs, Ipoh, Malaysia, 24 August-4 September, pp Dirk, L., Tonle Sap Fisheries: a Case Study on Floodplain Gillnet Fisheries. Asia-Pacific Fishery Commission, Food and Agriculture Organization of the United Nations, Regional Office for Asia and the Pacific, Bangkok, Thailand. Huxley, L.S Constant Differential Growth-ratios and their significance. Nature 114: GIWA Planning Workshop for detailed Impact Assessment, July Thailand. pp. 25. Karl, F. Lagler Fisheries and Integrated Mekong River Basinwide Fishery Studies. The University of Michigan School of Natural Resources. pp.85. King, M.,1995. Fisheries Biology: Assessment and management. Blackwell Science, London. Kolsovin, A. D. and M. B. Bain Fish assemblage recovery along a riverine disturbance gradient. Ecol. Appl. 3(3): Mark, T. Hill Fisheries Ecology of the Lower Mekong River: Myanmar to Tonle Sap River. Nat. Hist. Bull. Siam. Soc. 43: , MRC, Mekong River Awareness Kit. Mekong River Commission Secretariat (MRCS), Phnom Penh, Cambodia. MRC Report, State of the Basin Report: Executive Summary. Mekong River Commission, Phnom Penh, 50 pages. ISSN 1728:3248 Rainboth, W.J Fishes of the Cambodian Mekong. Food and Agriculture Organization of the United Nations Rome. Platts, W. S Classification of riverine riparian habitats for management of fisheries resources. U.S.D. A. Forest Service, Intermountain Research Station, Progress report 4 to Nevada Department of Wildlife. Hochachka, P.W. and Somro, G.N. (1984) Biochemical Adaptation. Princeton University Press, Princeton. ******* 13

14 Mekong River Commission Appendix: I Sheet No... Species Composition Location:. Date: Size of Gear: Area of fishing:.sq. m Species: No Species W (g) Price (US$) Duration of fishing: Minutes Total fish catch: Kg Sample catch: Kg No of fish (pcs) No Species W (g) Price (US$) No of fish (pcs) 14

15 Condition Factor Mekong River Commission Appendix: II Sheet No... Location:. Date: Size of Gear: Area of fishing:.sq. m Species: SL (mm) TL (mm) W (g) Depth (mm) Duration of fishing: Minutes Total fish catch: Kg Sample catch: Kg SL (mm) TL (mm) W (g) Depth (mm) 15

16 Fish Distribution and Abundance (Number of fishes) Appendix III No Scientific names LPB LPN LNO LVT LPS TM1 TM2 TM3 CBS CPP CUP No of Sites* 1 Cyclocheilichthys enoplos Puntioplites protozysron Barbodes gonionotus Paralaubica typus Sikukia gudgeri Mystus nemurus Helicophagus waandersi Henicorhynchus sp Kryptopterus cheveyi Mystus wolffi Osteochilus melanopleurus Sikukia stejnegeri Thynnichthys thynnoides Amblyrhynch. truncatus Cirrhinus microlepis Dangila sp. Cf. cuvieri Morulius chrysophekadion Osteochilus hasselti Oxyeleotris marmorata Raiamus guttatus Scaphognatops bandanensis Achiroides leucorhynchos Barbodes altus Barbodes schwanefeldi Botia eos Botia helodes Botia lecontei Botia modesta Channa striata Cyclocheilichthys lagleri Dangila kuhli Erythrospila Mekongina Hampala macrolepidota Helostoma temmincki Henicorhynchus siamensis Hetrobagrus bocourti Kryptopterus apogon Leiocassis siamensis Leptobarbus hoeveni Lobocheilos melanotaenia Lobocheilus quadrilineatus Lycothrissa crocodilus Macrognathus amartus Macrognathus siamensis macrognathus sp macrognathus taeniagaster Mastacembalus armatus Mystus amartus Nandus nandus

17 50 Notopterus notopterus Pacu (alien species) 6 1 Pangasianoidon 52 hypophthalmus Pangasius conchophilus Pangasius pleurotaenia Pangasius siamensis Paralaubuca rivreoi Poropuntius deauratus probarbus jullieni Puntius gonionotus 4 1 Remarks: * is number of sites, fish were distributed at. ******* 17