Effects of fish ladder on migratory fish species and fisheries in the Pak Mun Dam | |
| Author | Pradit Sripatrprasite |
| Call Number | AIT Diss. no.AQ-05-01 |
| Subject(s) | Fishways--Thailand--Pak Mun Dam Fishes--Thailand--Pak Mun Dam Fisheries--Thailand--Pak Mun Dam |
| Note | A dissertation submitted in partial fulfillment of the requirements for degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AQ-05-01 |
| Abstract | The Pak Mun Dam is the first run-of-river type dam in Thailand. It was constructed across the lower Mun River, 5 kms upstream from its confluence with the Mekong River. The Pak Mun Fish Ladder is the first of its kind installed at a hydropower dam in Thailand. A fish ladder was constructed to facilitate fish migration between the Mekong River and its tributary. The Pak Mun Fish Ladder integrated the overflowing weir and submerged orifice type with these dimensions: 4 m wide, 15 m high, 92 m long and a slope of 1:6. After dam was closed in 1994. There were many problems such as people and fishermen protested the EGAT. The protesters alleged fish could not ascending fish ladder, decreasing fish production, environmental change, human life change and required compensation. The aims of the present study were to evaluate effectiveness of the operation of fish ladder in number of migratory species and population size ascending the fish ladder, to determine the environmental change after dam construction, and to evaluate the fish and freshwater prawn production in the Pak Mun Dam. Two bamboo fish traps were installed to sample upstream and downstream fish migration at the exit of fish ladder during a 24 hr cycle for each monthly sample over one year period. Some physical, chemical and biological parameters were observed. The data collected from fishermen operating in reservoir and downstream include the number and weight of fish and freshwater prawn catch from May 1999 to April 2000. The measurements showed that discharge or outflow of the fish ladder was only 0.14 % of outflow of the turbine. The mean current velocity on the fish ladder was 0.6 m/sec. The upstream and downstream migration mainly occurred during the late hot season from mid May to early June. The rainfall increased numbers of upstream migratory fish. A total of 51 fish species were recorded in upstream migration and 29 species downstream. Cyprinidae accounted for 99 9 of the migratory fish species. The daily maximum number of fish migrated upstream and downstream was 3,541 and 490 fishes respectively. The estimated total fish weight migrating upstream was 11 % of fish caught in the reservoir. The ascending migratory fish species consisted of 70 % fish species found in the Pak Mull Reservoir. As most fish species collected were small juveniles, GSI was very low only 0.10-0.57 %, it indicated that those migratory fish were on small in size. The area of draw downzone was increased about 67 % in the reservoir. The overall of physical, chemical and biological parameters in the Pak Mun were not much changed. Average fish catch per fisherman at downstream (6.0±4.86 kg/day) was higher than at reservoir (1.4±0.78 kg/day). Fish catch in downstream (82 %) was more than at the reservoir (18 %) because it was under fish migration from the Mekong River to the Mun River. Fish yield of the Pak Mun Dam was 33.9 kg/ha/year. The average weight of prawn caught from the reservoir was 236.5±96.8 g. Freshwater prawn catch was 79.5 % from the reservoir and 20.5 % downstream. The total yield was 16,646 kg/year with a value of 122,027 USD/year (1USD=37 baht), contributing to 52.3 % of the total fish catch by weight (31,811 kg/year) and 98 % of economic value from the reservoir. Records show that prawn could be harvested 8 months after stocking with an estimated recapture rate of 1 %. Value of fish and freshwater prawn catch was about 0.52 million USD/year (3.3%). Energy sale of EGAT was 15.04 million USD/year (96.7%). Although results indicated that a large number of migratory fish was caught in the integrated fish ladder, the actual number of fish that successfully ascent to the reservoir was unknown and the fish ladder should be renovated for successful spawning migration. The freshwater prawn stocked program has been a successful effort in fishery management in the Pak Mun Dam. For multipurpose scheme to increase fish catch, fish migration, and electricity generation, the gate of the spillways of the Pak Mun Dam should be opened for 4 months from May to August and closed for 8 months from September to April. These operations were based on scientific information obtained from fish migration, water level in the Mekong River and downstream fish production |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AQ-05-01 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Aquaculture and Aquatic Resources Management (AQ) |
| Chairperson(s) | Yakupitiyage, Amararatne; |
| Examination Committee(s) | Chang, Kwei Lin;Suphat Vongvisessomjai;Cherdsak Virapat;Somsak Boromthanarat; |
| Scholarship Donor(s) | Mekong River Commission (Danida); |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2005 |