Does low water level of the Mekong River lead to scarcity of fish in Tonle Sap Lake?

Mr. Thach Phanara (L), an official at Inland Fisheries Research &Development Institute of the Fisheries Administration and Dr. Zeb Hogan, Project Leader of Wonders of the Mekong, study fish larvae migrating from Mekong River to Tonle Sap Lake...

PHNOM PENH--The Wonders of the Mekong Project in collaboration with the Inland Fisheries Research and Development Institute of the Fisheries Administration has conducted a study on drifting migratory fish fingerlings that migrate from the Mekong River to Tonle Sap Lake and other floodplain areas by drifting along the river currents after they hatch.


This study aims to investigate the amount of fingerlings and the diversity of species that release eggs that will later hatch into fingerlings. Its goal is to be able to evaluate the catch during the fishing season.


Normally, Siamese mud carp (Gymnostomus spp.) known as trey riel in Khmer, which make up much of the catch of freshwater fish in Cambodia, is the most abundant, along with other small species such as Paralaubuca spp. known as trey sleuk Russey in Khmer, Thynnichthys thynnoides known as trey linh in Khmer, Yasuhikotakia spp. known as trey kanh chrook in Khmer, and other big fish species such as Pangasius spp. known as trey pra in Khmer, Pangasianodon hypophthalmus known as trey pra thom in Khmer, Pangasius larnaudii known as trey por in Khmer, Cyclocheilos enoplos known as trey chkoak in Khmer, Hypsibarbus spp. known as trey chpin in Khmer, Small scale mud carp (Cirrhinus microlepis) known as trey kralang / trey proul in Khmer, Giant barb (Catlocarpio siamensis) known as trey kulraing in Khmer, and Giant catfish (Pangasianodon gigas) known as trey reach in Khmer.


At the beginning of the rainy season each year in early May, brood fish start releasing eggs into the upper Mekong River, especially along the deep pools in Kratie, Steung Treng and Ratanakiri provinces. Those eggs would hatch along the way then drift along the river currents to Tonle Sap Lake and other floodplain areas in order to find food and grow.


According to this recent study conducted in July, it shows that no fingerlings from any fish species have drifted along the river currents from the Mekong River to Tonle Sap Lake. This phenomenon is probably caused by the low water level of the Mekong River, which has not flowed and washed the fingerlings down into Tonle Sap Lake and other floodplain areas like in past years.


It is a concern here if the Mekong River water level is getting low when it is time for fish to migrate and spawn, as their life cycle routine will be interrupted, especially for Siamese mud carp (Gymnostomus spp.), Paralaubuca spp., and Thynnichthys thynnoides, which are a group of fish that potentially provide food protein to our Cambodian people.


Those fish will release eggs at the beginning of the rainy season and start to hatch along the way while drifting along the river currents. The fish larvae or fingerlings that just hatched cannot swim to anywhere far, instead they will swim around the same area and might be eaten by other fish.


The water level of the Mekong River that rises and falls in accordance with seasonal cycle is very important to fisheries resources. Thus, we all have to take part in protecting the Mekong River and our fisheries resources!


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