Pets released into the wild may be invasive species that cause biodiversity loss


Photos By ARNOLD LOH

This hard-to-reach ex-mining lake in Perak is teeming with native fish species like tiger barbs.

Turtles can be cute – but dangerous, too.

Someone released baby red-eared slider turtles into the small lily pond at the entrance of Penang Botanic Gardens recently. They were pretty little creatures but they were doomed from the start and their freedom did not last.

I watched the gardeners catch and cull them in November; the turtles would have eaten the water lily roots, killing the plants. Red-eared sliders are in the Top 100 Invasive Animals list of the International Union for Conservation of Nature.

They are natives of subtropical regions in the North American continent. They are aggressive and prolific breeders without predators in Malaysia to balance their presence in the circle of life here.

These baby red-eared slider turtles, released by someone into a water lily pond in Penang Botanic Gardens, had to be culled because they are an invasive species that kill the water lilies.These baby red-eared slider turtles, released by someone into a water lily pond in Penang Botanic Gardens, had to be culled because they are an invasive species that kill the water lilies.

While kayaking early this month on an ex-mining lake in Perak, I saw a marvel that made me remember those baby turtles.

Warm afternoon winds tend to be gusty on lakes, making paddling a kinetic struggle.

To give our arms a break, my paddling partner and I steered our kayaks to sit them on floating vegetation so we could rest without being blown about by the wind.

While resting, we caught sight of silhouettes of little fish at the edge of the weed line. Curious, I dribbled some of my berley (fish bait) directly below our kayaks to draw them closer.

My berley is a concoction of coconut milk, condensed milk and pandan essence diluted in a pail of water plus soaked, mashed bread.

Shortly, a shoal of hundreds of tiger barbs came. Some were less than 2cm long. Most others were at the adult sizes of 3cm to 4cm.

Dribbling a berley of soaked, mashed bread in a solution of coconut milk, condensed milk and pandan essence drew hundreds of tiger barbs up to the surface.Dribbling a berley of soaked, mashed bread in a solution of coconut milk, condensed milk and pandan essence drew hundreds of tiger barbs up to the surface.

Deeper down were bigger ones of around 5cm to 6cm. These were more wary and would not rise closer to the surface, so we could not photograph them.

How I regretted leaving my underwater camera at home. We spent close to two hours with the tiger barbs, trying (without success) with the berley to coax the bigger ones to rise so we could take photos with our phone cameras.

Other fish came, 10cm minnow-like fellas with black-tipped tails that zipped around like arrows.

We saw many other species but could not identify them because they were not as audacious as the tiger barbs to rise close to the water surface.

Tiger barbs swimming close to the water surface.Tiger barbs swimming close to the water surface.

Then it occurred to me: why did we have to drive kilometres off road to enjoy the sight of wild tiger barbs? They are not endangered, but why don’t we ever spot them in urban ponds and lakes?

It was a difficult drive. The dirt trail will thrash a city sedan’s wheel alignment and even crack the engine block from below. You have to use a 4x4 vehicle to get there.

But come to think of it, perhaps it is good that this lake of so many tiger barbs is difficult to get to.

Otherwise, people might drive over and release red-eared sliders and all kinds of fish, upsetting the ecosystem and probably causing the obliteration of the tiger barbs.

People release fish into public waterways for a few reasons.

The fish they had been keeping in an aquarium might have grown too big, or they simply no longer fancy an aquarium at home.

Many also release fish (by the bags) out of a religious belief that it is an act of merit, but before you exercise compassion, read up on natural sciences to be aware of the danger of biodiversity loss or throwing an ecosystem out of whack.

You can destroy an ecosystem if you release fish like the tilapia and African catfish because these are aggressive, grow and breed quickly and will monopolise that water body; they are meant to be bred only in fish farms as food.

In their native environment, fish like tilapia and African catfish have plenty of predators so they fit into an equilibrium there, but here in Malaysia, they will terrorise the waters.

Even if you release seemingly docile, herbivorous fish like grass or common carps (also invasive alien species), you introduce voracious feeders that will gobble up all the food resources and dominate the breeding sites.

The Department of Fisheries (DOF) lists 22 fish species that must never be introduced into our waterways.

It also lists 17 species that are excellent choices for release that will enrich ecosystems.

Every state has a DOF branch, so contact the branch in your state to learn which are the best species of fish to free into your state’s waterways.

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StarExtra , Outdoors , kayaking

   

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