By Jenissa Lawrence

There is a local legend about the cascadu that is passed on from generation to generation: if you eat the fleshy, freshwater fish, no matter where you roam, you will end your days in Trinidad. With local cascadu populations on the decline, however, fewer people may now have that assurance.

The University of the West Indies’ (UWI) Online Guide to the Animals of Trinidad and Tobago describes the cascadu as having “a body covered with tough armour which appears as long rows of bony scales, neatly packed along its sides as though they are intersecting each other for protection […] hence, the name armoured catfishes also given.”

While it is indeed a member of the catfish species, “with a broad head and two pairs of barbels projecting outwards from the chin area,” its scientific name is Hoplosternum littorale and it is native to Trinidad and the tropical Americas. Most commonly found in muddy, fresh water in the south and central parts of the country, the nocturnal species is dark brown to completely black in colour, which helps with camouflage when being hunted.

Yet, natural predators and fishing are not the primary reasons for the cascadu's decline. Four years ago, in August 2021, the Trinidad and Tobago Newsday reported that climate change is having an adverse effect on the species’ reproduction. Aquatic ecologist Ryan S. Mohammed explained that when the fish mate at the start of Trinidad's rainy season, which usually runs from June to December, the males build a floating nest for the female to lay her eggs. This is because the waterways they live in tend to have a low concentration of dissolved oxygen.

“With oxygen being key to the eggs’ survival,” he added, “the floating nest is made out of air, mucus and some vegetation. The eggs will remain just below the water's surface where they are kept properly oxygenated. However, the nest protects them from the high temperatures and direct sunlight found just above the water's surface.”

Since successful reproduction relies on a clear distinction between the dry and wet seasons, recent and often unpredictable changes to local weather patterns are contributing to the cascadu's decline.

In a telephone interview on April 10, 2025, Nirmal Ramoutar, a local cascadu farmer, said that temperature changes are also having a negative impact on the cascadu, which thrives in cool water. The species respires bimodally — the fish must intermittently come up for air — but when the temperature is too high, they will not surface.

Oxygen is also important for the survival of their eggs. Based on Ramoutar's observations, both the male and female cascadu build the nest, the top of which is made of grass or straw. The bottom, meanwhile — because it contains oxygen — looks like froth. He has noticed that as many as 15 females can lay eggs in one nest; after laying, however, only the male remains to take care of the thousands of eggs.

A 2021 article in the Trinidad and Tobago Express by environmentalist Heather-Dawn Herrera noted a decline in the cascadu as a result of not just climate change, but also human impacts like chemical run-off from agriculture. Despite these adverse effects, Ramoutar remains hopeful that rearing the fish in private ponds, thereby providing a suitable environment for them to thrive, can replenish their population.

In an effort to mitigate the effects of higher temperatures, Ramoutar grows lilies and water hyacinth to help keep the water cool. However, he must also ensure that these plants do not overcrowd the pond and prevent the cascadu from surfacing for oxygen.

Another effect of the climate crisis that Trinidad and Tobago has been experiencing is a significant increase in rainfall, which Ramoutar says also affects the cascadu. Flooding, for instance, can wash away nests, affect the ability of the fish to surface for air, and lower the oxygen content in the water, making it more difficult for them to breathe.

If these damaging effects are left unchecked, it could eventually lead to the extinction of this unique freshwater fish — and by extension, the eradication of a rich aspect of the country's cultural heritage. But, by protecting its habitat, monitoring water quality, and promoting sustainable practices, future generations can continue to enjoy the cascadu and keep its legend alive. [GlobalVoices/VS]

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