Spring Baby Bounce for Mekong River Dolphins

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Mekong River dolphins and calf. Photo: WWF

Wildlife rangers in Cambodia have sighted 3 new Mekong River dolphin calves born during the spring breeding season this year.

Conservation group WWF, which funds research and protection of the rare dolphin in Cambodia, says the 3 new dolphin babies are a very healthy increase for the total population of just 80 Mekong dolphins.

And the WWF wildlife rangers also reported no signs of adult dolphin deaths during their spring survey of the remote pools in the Mekong where the dolphins live during the low-river season, which is often a perilous time.

The Mekong dolphins are a unique population of Irrawaddy dolphin, named for a river in Myanmar where the species is also threatened. Most Irrawaddy dolphins live near river estuaries and the sea. But the Mekong dolphins are far from the sea and most live their whole lives in the river. In Cambodia only 80 dolphins remain in a stretch of the Mekong River between Kratie province and the Laos border to the north. Another group of about 5 dolphins live in the Mekong below the Khone Falls in Laos.

WWF funds scientific research and protection programs for the Mekong dolphins from a base in Kratie.  Protection efforts include encouraging local fishermen to reduce the use of set gill-nets, which can entangle dolphins attracted to the netted fish.

Source: WWF

Mekong: a river rising | The Guardian

 

The fate of 70 million people rests on what happens to the Mekong river. With world leaders meeting in Paris for crucial UN climate talks, John Vidal journeys down south-east Asia’s vast waterway – a place that encapsulates some of the dilemmas they must solve. He meets people struggling to deal with the impacts of climate change as well as the ecological havoc created by giant dams, deforestation, coastal erosion and fast-growing cities

John Vidal’s first stop along the river is the tiny country of Laos. Fifty years ago, Laos began to build a series of giant dams. It was the first chance the country had to generate the electricity and money needed to emerge from deep poverty. But is this demand for clean energy creating ecological and human havoc?

Read more at Mekong: a river rising / The Guardian

Thailand Eyes Mekong & Moei Water Diversion to Control Drought & Flooding

Rasi Salai Dam

From: Many areas are flooded while others remain parched | Thailand PRD 6 August 2015:

quote1Meanwhile, Sisaket residents are still coping with the drought crisis as the amount of water in the Rasi Salai Dam is at a critical level. Only one of the sluice gates is opened to release water into the streams, in order to conserve the remaining water.

From: RID pushes two new water diversion bids | Bangkok Post 18 July 2015:

quote1[Mr Thanar said] the other project would divert water from the Mekong River to the Chi and Mun rivers in the Northeastern region. The project starts from Chiang Khan district in Loei where water from the Mekong River would be diverted into a new, 100-km canal which will be dug under the project.

The canal will be the water course sending the water into the two rivers in the Northeastern region. The project could feed more water into Ubolratana dam in Khon Kaen and nearby reservoirs. Upper Northeastern provinces will also reap benefits from the project such as Nong Bua Lam Phu and Loei.

The projects, under the department’s 10-year plan, will be forwarded for approval to the National Water Resources Committee, chaired by Prime Minister Prayut Chan-o-cha, in its first meeting next Wednesday. The committee was set up last Wednesday, said Mr Thanar.

Vietnamese plea to Thailand: Don’t divert the Mekong | The Nation Thailand

quote1[Thailand’s] Prime Minister Prayut Chan-o-cha voiced plans to use water from the Mekong and Salween rivers to fill dams that have run low because of drought and poor water management. But the PM’s remarks have caused shockwaves in the [Vietnamese] Mekong Delta, which would be directly affected if such a project was to go ahead.

Nguyen Huu Thien, a freelance expert on wetland ecology and natural resource conservation, criticised the idea. He said taking a large amount of water out of an international river was like sucking the blood from a body and would surely hurt the livelihood of people downstream.

“I just heard of Thailand’s idea to divert water from the Mekong River. I still don’t have much information about the plan but I strongly oppose this idea, as a change in the amount of water in the river would definitely have an impact on the people who live in the Mekong Delta and who rely on the river,” Thien said.

From: Vietnamese plea to Thailand: Don’t divert the Mekong | The Nation Thailand

Siamese Mud Carp and Hydroelectric Dams in the Mekong River Basin (Various Studies)

From: Potential Effects of Hydroelectric Dam Development in the Mekong River Basin on the Migration of Siamese Mud Carp (Henicorhynchus siamensis and H. lobatus) Elucidated by Otolith Microchemistry by Michio Fukushima, Tuantong Jutagate, Chaiwut Grudpan, Pisit Phomikong, Seiichi Nohara, 6 August 2014

quote1Of the vast multitude of fish species in the Mekong River, two closely-related species, Henicorhynchus siamensis and H. lobatus, are of special concern given the rapid rate of hydropower development. Inhabiting the Mekong and Chao Phraya basins (H. siamensis) and the Mekong basin (H. lobatus), these two small-sized cyprinids, collectively referred to as Siamese mud carp, are the most abundant and most economically important fish in the middle and lower Mekong basin. They are harvested in huge numbers, especially in and around Tonle Sap Lake in Cambodia and the Khone Falls area in southern Laos. These species account for 43% and over 50% of the total catch in these areas, respectively, with an overall basin-wide catch being >12% for the two species combined.

quote1The Siamese mud carp populations in the Mekong, or at least some of them, are known to perform long-distance migrations. However, what is known about their migrations is severely limited. In Thailand and Laos, the species undertake upstream migration in the early rainy season above the Khone Falls, whereas in Cambodia, this species migrate upstream at the onset of the dry season below the waterfalls. The latter migrants possibly originate from the Tonle Sap Lake, first descending the Tonle Sap River and then ascending the Mekong mainstream toward and even past the Khone Falls . Spawning takes place in tributaries or floodplains during the wet season, with a peak in May-June. Eggs and larvae are carried to nursery habitats on the floodplain by the water current. At the beginning of the dry season, juveniles move out of the floodplains with the receding water and seek dry season refuge habitats such as deep pools in the Mekong mainstream.


From: Population subdivision in Siamese mud carp Henicorhynchus siamensis in the Mekong River basin: implications for management. Adamson EA1, Hurwood DA, Baker AM, Mather PB. 2009

quote1A molecular approach was employed to investigate stock structure in Siamese mud carp Henicorhynchus siamensis populations collected from 14 sites across mainland south-east Asia, with the major focus being the lower Mekong River basin. Spatial analysis of a mitochondrial DNA fragment (ATPase 6 and 8) identified four stocks in the Mekong River basin that were all significantly differentiated from a population in the nearby Khlong River, Thailand. In the Mekong River basin, populations in northern Lao People’s Democratic Republic and northern Thailand represent two independent stocks, and samples from Thai tributaries group with those from adjacent Mekong sites above the Khone Falls to form a third stock. All sites below the Khone Falls constituted a single vast stock that includes Cambodia and the Mekong Delta in Vietnam. While H. siamensis is considered currently to undertake extensive annual migrations across the Mekong River basin, the data presented here suggest that natural gene flow may occur over much more restricted geographical scales within the basin, and hence populations may need to be managed at finer spatial scales than at the whole-of-drainage-basin level.

From: ‘The migration pattern of Trey Riel, Henicorhynchus siamensis, in the Mekong mainstream’ Chan Sokheng, 2000?

quote1Below the Khone Falls, H. siamensis migrates upstream from November to February, whereas above the Khone Falls, it migrates upstream from March to September. It migrates in response to changing water levels. As floodwaters recede H. siamensis migrates from the flooded areas back to main river channels, e.g. the Mekong mainstream. Several fishers below the Khone Falls reported that the peak period of upstream migration for H. siamensis occurs one week before the full moon. Above the Khone Falls, migrations appear to be less influenced by the lunar phase. Some fishers along the stretch from Kratie to the Khone Falls in Cambodia were able to determine the speed of migration based on the time it takes for the fish to move between two villages along the river. They estimated the speed at 16 km per day… Below the Khone Falls, H. siamensis migrates downstream from May to September when the water levels start to rise. This corresponds with the peak time for observations of eggs in the fish, i.e. the peak spawning period is believed to occur between May to June.

quote1Migration is usually linked to changes in the water levels. When water levels start to rise during the flooding season, fish migrate from the Mekong mainstream to canals and flooded areas. Near the end of flooding season fish migrate back to the larger rivers. In the Mekong mainstream upstream migrations occur from November to February and downstream migrations from May to September (below Khone falls). The patterns of migration described below the Khone Falls differ from observations made in northern Lao and Thailand, where migrations take place from November to February. This could indicate that a different sub-population is involved in that section of the river. It should be noted that fishers catch this species all year round.

2015-08-15 16_08_52-www.mekonginfo.org_assets_midocs_0001336-biota-the-migration-pattern-of-trey-rie

 

From: ‘Life history of the riverine cyprinid Henicorhynchus siamensis (Sauvage, 1881) in a small reservoir’ by A. Suvarnaraksha, S. Lek, S. Lek-Ang and T. Jutagate. Journal of Applied Ichthyology, August, 2011

quote1Fish of the genus Henicorhynchus are small migratory cyprinids and one of the most important groups in the Lower Mekong Basin and Chaophraya River basin fisheries, especially the Siamese mud carp Henicorhynchus siamensis (Sauvage, 1881). This fish is a common catch whereby in thebasin area four sub-populations were recently identified (Adamson et al., 2009). H. siamensis is also the main fish catch produced by the commercial bag-net fisheries in Tonle Sap, Cambodia, where it constitutes more than 60% of the catch and accounts for almost 10% of the total value generated (Deap et al., 1998). Moreover, H. siamensis is ranked as the top species commonly consumed by Cambodians. These advantages play a crucial role as the most important animal food for the poor (Kent, 1997) and also fulfill a role as a dietary source of vitamins and minerals (Rooset al., 2007). The importance of this fish is also acknowledged in the Cambodian currency, the ÔrielÕ, which is named after the Cambodian common name for H. siamensis of “trey riel” (Volbo-Jørgensen and Poulsen, 2000).

quote1H. siamensis is also well known for its migratory habit oflateral migration into the floodplains during the flood season and then returning to the rivers when the flood waters begin torecede (Rainboth, 1996). But it is also known not to prosper inimpoundments (Lamberts, 2001; Chheng et al., 2004), as itslife cycle depends on the river ⁄ flood regime. However, H. siamensis can successfully inhabit man-made lakes in Thailand as well as in the Lao PDR, and is among the candidates for a fish stock enhancement program to increase fish production in inland water bodies in the region (Jutagate 2009). Knowledge of the life cycles of many important SoutheastAsia freshwater fish species is still very fragmentary, especially when they inhabit an uncommon environment (Volbo-Jørgen-sen and Poulsen, 2000). Given the importance of H. siamensis to fisheries in many parts of major Southeast Asian rivers, this study aimed to investigate the key facets of the H. siamensis life history (Froese et al., 2000), i.e. reproduction, feeding and growth. A goal was to see whether this small cyprinid could flourish and support a small-scale artisanal fishery in a reservoir and to evaluate its potential as a source of protein and micronutrients as well as income for the local people in the vicinity of the reservoir.

‘On the River of No Returns: Thailand’s Pak Mun Dam and its Fish Ladder’ (2001 Study )

Pak Mun Dam

From ON THE RIVER OF NO RETURNS: THAILAND’S PAK MUN DAM AND ITS FISH LADDER, Tyson R. Roberts, ThaiScience 2001 (pdf)

Most fish species living in the Mun River are unable to climb or are for other reasons not using the ladder installed on Pak Mun Dam. This is especially true for large species most important in wild-capture fisheries. The ladder is unsuccessful in maintaining fish spawning migrations because few or no gravid females of any species climb it. Various proponents of Pak Mun Dam claim that its main impact on fish is that they cannot swim upstream and downstream past the dam. This is far from the only impact. The real problem is not with the ladder. Rather Pak Mun Dam itself is ecologically unfriendly to fishes.

A reservoir outflow is not a normal river. The abnormal flow regime and other artificial features in the outflow of Pak Mun Dam have severe impacts on fishes for 4.5 km until it joins the Mekong mainstream which dissipates (but is also effected by) its negative impacts. Pak Mun Reservoir is also very unfriendly to fish. This apparently is due mainly to having its bottom smothered by silt and its open water with an exceptionally heavy silt load at all times because of the highly abnormal “run of the river” flow conditions.

When the water level in Pak Moo Reservoir is at 108 m. “peak electricity generation” causes daily fluctuations in water flow downstream from Pak Mun Dam and daily draw-downs in the reservoir that disturb fish habitats and disrupt fish migration. If reservoir water levels are too low, the amount of water released from the sluice gates may be less than the lowest flow that normally occurs for only a few days or weeks of particularly dry years (if the reservoir level falls below 94 m the outflow will stop altogether). During minimum outflow the water quality also can be much poorer than that of normal dry-season low water without the dam. The other extreme occurs when water has to be released to prevent the reservoir itself from over-flowing. Opening the sluice gates on the spillways when the reservoir level is high can create a destructive torrent far stronger than any that occurred during the worst floods in the Moo River before Pak Moo Dam. Maximum as well as minimum outflows from Pak Moo Reservoir are lethal to fish.

The problem of Pak Mun Dam and fisheries may be summarized as follows: an artificial and hostile downstream environment (reservoir outflow) and an artificial and hostile upstream environment (reservoir) are connected by artificial and hostile corridors (fish ladder and dam spill-ways). The resulting impact accumulation has devastating over-all effects on fish habitats and fish species. Pak Mun Dam together with its 35-km long reservoir and 4.5 km reservoir outflow is a major geographic barrier to all kinds of fish movements between the Mekong and the Mun.

China Should Join Mekong Commission: US Official

China should join an intergovernmental commission supervising development of the Mekong River to more effectively address environmental and other problems faced by downstream Southeast Asian nations, a senior U.S. government official says.

Aaron Salzberg, special coordinator for water issues at the U.S. State Department, also underlined the importance of political will in ensuring that the Mekong River Commission (MRC) functions as an effective forum in coordinating shared use of the region’s main waterway.

“In the long run, I think it would be good for China to become a full active member in the MRC … sharing data so that the downstream countries actually understand what’s going to happen and when it’s going to happen and they can prepare accordingly for those types of things,” Salzberg told RFA.

“China can play an active role in managing their infrastructure for downstream benefits,” he said.

Five dams commissioned in China on the Mekong river’s upper portion have caused rapid changes in water levels and other adverse effects downstream, especially in the four countries of the Lower Mekong Basin—Vietnam, Cambodia, Thailand, and Laos—where tens of millions of people depend on the river for food, water, and transportation, environmentalists say.

China has refused to join the MRC—which comprises the four lower Mekong nations and manages development along the Mekong—although the river’s source is located within the Asian giant’s borders, saying it prefers to negotiate on a bilateral basis to resolve any problems on the issue.

via China Should Join Mekong Commission: US Official.