A few months ago, we heard about unique arrow-shaped fish traps in Cambodia from Fulbright Scholar, Elizabeth Everest. We check back in with Elizabeth to learn about invasive and native snails and how they are sold, eaten, and perceived by locals.

Guest Author: Elizabeth Everest

Editor: Patrick Cooney

Snails may be slow, but the seasons change fast on the Tonle Sap

A month of hot, dry weather had worked wonders on the waters of the Tonle Sap Lake in Cambodia.

The flooded forests were now impassible by boat due to low water levels. A lush growth of flooded grass, stretching hundreds of meters from the tree line all the way the open-water lake, was now the defining characteristic of the shoreline.

We were back in Siem Reap, specifically on a hunt for snails, native Pila sp. and invasive Pomace sp. Our mission was to chat with our fisher friends about the impacts of the invasive snails on their livelihoods and document how they were sold, eaten, and perceived by locals.

Throughout Cambodia, particularly in the wet season, hundreds of tons of snails are sold in markets every year. Pomacea sp. was introduced in the 1990s from South America for food cultivation but has since become a pest, damaging rice crops and out-competing native snails (Khay et al. 2018). For some species, it is easy to identify the difference, and fishers sell native snails for higher prices because they are believed to taste better.

Despite their importance to the local ecosystem and economy, gastropods in the Tonle Sap have not been thoroughly researched. Most of what we know is based on records from the 1800s and early 1900s (“A First Look At Mollusc Diversity”. 2021). While helpful, these records sometimes misidentify species or only identify them to a broad taxonomic level (Ng et al. 2020).

During an extensive survey in 2019, Wonders of the Mekong scientists worked to identify and classify Tonle Sap macroinvertebrates, including snails and clams. They actually identified 16 unique species of snails (Ng et al. 2020)! Further efforts are needed in this area, but that day we were focusing on the most commonly sold species, apple snails (family Ampullariidae).

Our flooded forest arrow-shaped trap contained nearly 100 lbs of snails in February, but that trap had since been moved, so we needed to search for snails in a new location. Braving swarms of dragonflies, we attempted to reach the forest by crossing what had been open water but was now an expansive grassy marsh. Even our shallow hulled boat could not push through the thick grasses with so little water.

While we didn’t find any snails in that area, the green shoots held indicators of the invasive snail’s pervasive presence. Surrounding us on all sides, visible on hundreds of blades of grass, were clusters of pink snail eggs looking like miniature soap bubbles the color of Glinda the Good Witch’s dress. The vibrant pink color of Pomace sp. eggs sets them apart from white Pila sp. eggs.

We turned the boat around and headed back out in search of an area that might be more accessible to the forest. We hoped we were on the right track when the fishers took us to a channel constructed for a road construction project that supplied us easy access to the shore. Waving to the young men tossing their spinning cast nets into the water, we wove our way past several mini arrow-shaped traps to the edge of the forest.

There they were! With the fishers help, we squelched through calf-deep mud, collecting as many shells as we could find. The tropical sun had warmed the mud and water to the temperature of a hot bath, and with each step, I had to carefully extract my sandal so as not to lose it.  In the dry season, so close to open water, there were far fewer snails than there had been during our trip in February. Still, we were able to collect enough for our late lunch, and we headed back to the floating village of Chong Khneas.

While some snail species are more difficult to tell apart, the invasive and native apple snails are distinctly different. Our local friends explained how they identified each type. The invasive Pomacea sp. had a deeper grove, called a suture, in the shells’ spiral. They also had a deep dent where the inner lip of the shell opening met the main shell.

Pila sp. shell sutures are flush and have no groves. The inner lip of the shell opening also connects smoothly to the main body of the shell.

They also identified an additional native apple snail based on its coloring; they were more common in rice fields than in the lake.

Based on their experience, the invasive snails did not fetch as good a price as the native snails, but that didn’t stop them from being delicious.

We separated the snails into two piles and proceeded to prepare them for lunch. Half our snails went into a large pot with lemongrass, chicken stock, sugar, and salt to be boiled.

The other half were removed from their shells, and the muscular foot saved and sliced for sautéing.

Into a mortar and pestle, we put chilies, salt, sugar, and lime juice, which were all pounded into a thick paste. While the other pot bubbled away, our sliced snails sizzled in garlic and chili paste, and I have to say it smelled incredible.

Everyone, kids included, gathered for the feast. Using toothpicks, we slid the boiled snails right out of their shells and into our mouths. Our sautéed snails we enjoyed on rice, and they sure tasted good after a long hot day in the sun!

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About the Guest Author

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.