Tonle Sap: The Heartbeat of Cambodia

Introduction to Tonle Sap

Tonle Sap is the largest freshwater lake in SE Asia. Literally, Tonle translates to English as “fresh” and Sap translates as “lake”. However, the significance of the lake is that it’s fishery sustains the livelihoods of over 1,000,000 inhabitants who live in the surrounding provinces. Tonle Sap was also the food source that sustained the ancient Khmer city of Angkor. It is no coincidence that location of Angkor was in close proximity to the lake.

The Heartbeat of Cambodia

The great lake is connected to the Mekong river by the 75 mile long Tonle Sap River. When the Mekong enters its seasonal flood stage the result is that the Tonle Sap River reverses course. This phenomenon is caused because the Mekong overpowers the water flowing downstream from the great lake. As a result, the water is now flowing into Tonle Sap instead of exiting it and the size of Tonle Sap fluctuates greatly during the year. Hence, this expanding and contracting of the lake is metaphorically compared to a heartbeat.

Subsistence Fishing

The local villagers primarily use nets to capture the fish. Mostly, the fisherman do everything manually although a few of them are able to afford more automated equipment. The video below demonstrates one of the more automated fishing operations on the Tonle Sap tributary we were traveling on. Unfortunately, many families who rely on fishing do not have access to the more modern equipment.

In contrast, the vast majority of the village fisherman must manually work their nets. The fishing nets are tethered to the shoreline or to their boats. When traveling up the tributary rivers avoiding the positioning of these nets is like traveling through a maze.

fishing on tonle sapThe fishing nets are spread out across the water leaving only a narrow passage way.

fishing on tonle sapThese are shore based fisherman in a more narrow stretch of the river. 

The catch of the subsistence fisherman is commonly prepared by grilling or smoking over an open fire.

fishing on tonle sap

Although it would be considered a delicacy for most of the locals, other food sources such as small turtles and snails are also consumed. We were served a variety of local food when we attended the Prey Chas school opening ceremony.

food diversity on tonle sap


Unfortunately, the sustainability of the Tonle Sap fishery resources is not certain. As of 2007, the Tonle Sap’s largest commercial fishing operations reported that their annual catch has been consistent year over year. However, the subsistence fisherman report that their annual take has dropped by 50-70% over the previous decade. Additionally, the size of the fish being caught has dropped substantially with a much higher proportion of smaller fish. This implies that the fishery is becoming depleted and the resources are not being replaced.

Traveling on the Tributaries

There is a ferry service that operates in between Siem Reap to Battambang. The route passes across the northern tip of Tonle Sap and enters the tributaries in order to get to Battambang. Unfortunately, every year there are fatalities caused from the passing wake created by the larger ferry boats. This is because the wake can capsize the smaller fishing boats and the occupants drown in the river.

However, even for the ferry travel is not easy as they can become stranded on mud banks or the propeller can get entangled in river plants.

travel on the tonle sapThe propeller is caught up in the undergrowth of the river.

While we were traveling from Battambang to my Prey Chas, Cambodia community development project we used some less traveled sections of the tributary rivers.  This was done more efficiently in a smaller and faster moving boat.

Flooding on Tonle Sap

The reversal of the Tonle Sap river results in a massive increase in size of Tonle Sap. Therefore, villages surrounding the great lake must be able to stay above the high water line. The construction of the houses and public buildings in Prey Chas reflect this necessity. 

The local school is situated 15 feet above ground to stay above the flood line. Buildings that are not elevated must be able to float on the water surface of they will become inundated during the flood season. 

construction on tonle sap

The construction of local homes in Prey Chas must take into account the fluctuating water levels of the great lake.


Sustainability of the Tonle Sap fishery is essential for the survival of the inhabitants of the surrounding provinces. Unfortunately, the Cambodian government has limited resources to regulate over fishing. It can be inferred that the commercial fishing industry is under reporting their annual catch which explains why the subsistence fisherman are reporting sharply dropping catch levels. Subsistence fishing now requires significantly more effort to procure enough fish to survive on.

I last traveled through the Prey Chas area in November 2014 to attend the school opening. We made use of small open boats and I was astounded by the the number of fish that were apparent to the naked eye. This was because small fish were literally jumping into the boat as we traveled over the water. Fortunately, the virility of the Tonle Sap seems to be holding up for now. 


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