Guest Author: Elizabeth Everest. Editor: Patrick Cooney

The Journey Begins

As we completed our journey across the lake, our boat slid towards a seemingly impenetrable wall of tropical greenery. I looked back over my shoulder at the wide expanse of the Tonle Sap lake and thought, “Toto, I’ve a feeling we’re not in Nevada anymore.”

The narrow hull barely slipped between the trees in the flooded forest.  I quickly became aware that only the local fisherfolk could find this hidden track through the undergrowth.

After a few moments immersed in the tangled understory, the ceiling lifted, and we drifted out into a serene lagoon canopied by overarching boughs.  A foreign object with unnatural angularity stood in the middle of the lagoon, juxtaposed to the soft foliage of the surrounding scenery. Secreted away from the outside world, with its mesh net walls stretching 100m in either direction, the foreign object was an arrow trap, the design perfected over hundreds of years by local Cambodians to catch fish.

Considering that it had been three weeks since I arrived in Cambodia, and this was my first day in the field, you can bet that I was excited to put my hands on some fish!

However, just a few short months ago, the reality of sitting in this boat surrounded by emerald green vegetation seemed as unobtainable as Dorothy reaching the Emerald City of Oz. 

Tonle Sap

A year ago, I was selected as a Fulbright Scholar to work with the US-AID funded Wonders of the Mekong (WOM) project in Cambodia to conduct research on the fisheries of Tonle Sap lake and river. Challenges associated with the COVID pandemic delayed my travel plans, but never-the-less, I persevered, and here I am.

Often referred to as “the beating heart of Cambodia,” the Tonle Sap lake is the largest lake in Southeast Asia. As rains fall between May and November, the Tonle Sap lake quadruples in size as rising water from the Mekong flow to the Tonle Sap river.

In the dry season, the waters recede, rushing back down the river in a seasonal pulse that floods the land and forests with nutrients.

This rhythmic rise-and-fall is what gives the Tonle Sap its “beating heart” nick name.  Just like a heart sustains a body, the Tonle Sap sustains one of the most productive and biodiverse freshwater fisheries in the world.

Its natural riches have made the Tonle Sap a central feature in the traditions and lives of the Cambodian people. The abundant fishery supports the livelihoods of millions of Cambodians and provides the dominant source of protein for the Lower Mekong Basin. However, the future of the Tonle Sap and its people are threatened by increase human demand on the landscape.

Construction of hydropower dams, conversion of flooded forests into farmland, and overharvest of fish put the sustainability of this recourse at risk. The WOM project brings together dedicated researchers from around the world to investigate how this fishery functions and find solutions that will preserve this incredible ecosystem for future generations. I am honored to spend a year working alongside them.

Arrow Traps

One of the current WOM initiatives I am excited to work on focuses on investigating arrow shaped traps in the Tonle Sap Lake. Arrow shaped traps are just one of many types of gears operated by the fisherfolk of the Tonle Sap. They are constructed of bamboo/wooden poles and fencing and can measure up to 500 m long. Traps are usually made up of 1-3 layered entrances, shaped like arrows, which funnel fish towards the final “capture room”.

Fishers use arrow traps year-round in the flooded forests and open waters of the Tonle Sap Lake. During the rainy season, arrow shaped traps can be found scattered throughout the flooded forest and rice fields surrounding the Tonle Sap Lake. As waters in the fields and forest recede in the dry season, traps are moved out of the forest into open water.

While these traps have been used widely by local fishers for many years, little is known about their impact on the lake fishery, how much fish they catch, and how the catch contributes to the economy of Cambodia. The Wonders of the Mekong research team is on a mission to answer these questions.

Back in the beautiful Tonle Sap lagoon on my first field day in Cambodia, our objective was to collect the catch from three separate arrow traps. The fisher who owned the traps is cooperating with WOM to sample the catch every other day throughout 2021.

Being in the dry season, most of the arrow traps had been moved into the lake.  However, one remained tucked in the flooded forest. Before we collected the catch from that first trap, we had a thrilling side venture to complete.

Pythons: Food for thought

Arrow shaped traps often catch more than just fish. That day, the traps had two pythons that needed to be released back into the wild.  Pythons are nonvenomous and play a vital role in the ecosystem of the Tonle Sap.  While many local people choose to keep these snakes for food or for selling in the market, these fishers decided to release the snakes back to their home.

Standing carefully in the prow of the boat, our guide hefted one snake at a time from a burlap sack. I gazed in shock and wondered at the size and strength of the pythons before helping to toss them back into the water to watch them disappear into the shadows of overhanging trees.  

Local fisheries officers and managers hope that more individuals will take opportunities to release these incidentally captured animals back into the wild in order to support the environment and open opportunities for eco-tourism.

With our snake friends freed, we proceeded to collect the catch from the first trap.  As the fishers hauled the “capture room” out of the water, it was evident that the small numbers of fish and the single frog were drastically outnumbered by hundreds of golden apple snails (Pomacea sp.).

Fish and Snails

Transplanted from South America, the golden apple snail has become widespread throughout the Tonle Sap and Mekong where it is a pest for farmers and crops. This trap contained over 40 kg (90lbs) of snails!

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Scattered among the multitude of shells were snakeheads (Channa sp.), three spot gourami (Trichopodus trichopterus), Ompok siluroides,and a few freshwater crabs, each of which I admired as we made our way out of the forest and back into the sunlight.

The next two traps were in the open water, and while these catches were not as large as the first with all its snails, they were rich with a variety of unique species and a surprising number of tiny translucent freshwater shrimp.

Having collected our samples, we headed back to the shade of the lake house in the floating village and prepared for an afternoon of sorting, identifying, counting, weighing, and measuring the species from each trap.

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I intend to keep you posted on my adventures in Cambodia before I click my heels together and wake up once again in Nevada in a year’s time.

See more photos of the arrow traps and the people who construct them.

About the Guest Author: Elizabeth Everest

Elizabeth Everest was born and raised in Carson City, Nevada. After spending a year abroad in Thailand, she was inspired to return back to her community in Nevada and start making a difference. While achieving a Bachelor of Science Degree in Biology at the University of Nevada, Elizabeth worked with several leading researchers on a project in the Mekong River as well as a project closer to home in Lake Tahoe. Her current journey as a Fulbright Scholar has taken her to Cambodia’s Tonle Sap lakes and rivers where she is working with the Wonders of the Mekong project to assist local organizations in gathering fish population data. She is collecting data of fish mortality and migration in conjunction with a new hydroacoustic monitoring system in the Tonle Sap river. She is also interviewing subsistence fishers about changes in fish population trends—a continuation of a project she took part in as an undergraduate. Together, these two data sources can provide policymakers and the public with insights into how fish populations in the Tonle Sap are changing and support the development of management solutions in the future.