Cambodia's Tonle Sap World's #1 Inland Fishery; Dams, Drought Force Restocking Of Key Food Species
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In recent years, the combined threats of overfishing, drought, habitat destruction and the impacts of upstream dams on the Mekong River’s natural flow have wreaked havoc on fish populations and aquatic habitats throughout the river system. Tonle Sap Lake, a UNESCO Biosphere Reserve, lies within the Lower Mekong Basin. During the wet season, between June and August, the lake can swell to five times its size as the Mekong River’s annual flood pulse surges up the Tonle Sap River, flooding the lake’s surrounding forests and wetlands. These habitats are crucial nurseries for more than 300 species of fish, whose larvae are carried downstream into the lake by the flood pulse.
As a result, the lake is home to the world’s most productive inland fishery, clocking annual fish catches of up to 400,000 metric tons. However, abnormally dry conditions in recent years due to droughts and a weakened flood pulse from the Mekong, in part due to upstream engineering, have severely depleted catch sizes.
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Notwithstanding the many benefits of the fish releases, they are just one small part of an overall solution to plummeting fish numbers, according to Hogan. Crucially, measures must be taken to protect the fish during all stages of their lives. This also means safeguarding migration corridors like the Tonle Sap River and spawning grounds in upstream parts of the Mekong River, he said. Maintaining the Mekong River’s natural flow regime is also vital: the river’s flow prompts fish to set off on their upstream spawning migrations and carries young fish downstream to their nursery habitats in Tonle Sap Lake.
With the Mekong’s annual flood pulse weakening as a result of droughts and upstream engineering, scientists are concerned that fish are less able to successfully complete these crucial life stages that give rise to the next generation.
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https://news.mongabay.com/2022/03/cambodian-project-aims-to-revive-flagging-fish-populations-in-tonle-sap-lake/