RIVER DWELLERS

I visited the river right after the recent monsoon rains and noticed dozens of people flocking to the rivers. Whenever heavy rains washed over the mountains of the Sierra Madre, Fish from the floating farms of Laguna Lake sometimes escaped down the Marikina and Pasig Rivers. There were Knifefish and Cream Dory, some as heavy as 20 pounds!

Through the years, I’ve noted what fishes were in the river. As a young student in UP and Ateneo 20 years ago, I clearly remember the Marikina River having bottom-dwelling gobies called Biya, spear-shaped halfbeaks called Kasuswit, climbing perch called Martiniko who can briefly crawl on land to reach the next muddy pool, colorful Gouramis, and a host of other Fish.

Today, invasive Fish have taken over the river. Hailing mostly from Africa, South America, and Indochina, they have successfully adapted to Philippine waterways – which is bad news for our native Fish.

What can happen down the line if these invasive fish continue to swim in our rivers? Let’s take a look at what’s currently happening in Africa.

In East Africa’s Lake Victoria, the introduction of Nile Perch has proven disastrous. In an attempt to “boost fisheries productivity”, the predatory Fish were introduced to the lake in the 1950s. Growing over six feet long, they soon preyed on over 100 other Fish species, practically wiping out 60% of the lake’s native Cichlids in what may be the largest vertebrate extinction of the 20th century.

As you read this, thousands of brightly-colored Cichlids (one species alone is worth Php 2,000 apiece, compared to Nile Perch selling for Php 200 per kilogram) are being eaten hourly. The Philippines has already experienced a similar phenomenon, with at least 15 fish species declared extinct in Lake Lanao.

“This is not the first time we are witnessing the impacts of invasive alien species, which eat or outcompete native species,” says Dr. Theresa Mundita Lim, executive director for the ASEAN Centre for Biodiversity, an intergovernmental body that protects and conserves the ASEAN’S biological diversity.

“While the introduction of invasive alien species like [T] ilapia or [P]angasius may be perceived as valuable for livelihoods, food production or pest control, science-based assessments should be undertaken to determine if it leads to adverse impacts on the environment and biodiversity. We should ensure that this will not bring more harm in the long run,” adds Lim. According to her, the extinction of native species affects nutrition, food security and dietary diversity. This leads to numerous local, national and regional implications.

According to the ASEAN Biodiversity Outlook 2, ASEAN member states have identified 112 invasive alien species affecting forests, agriculture, and aquatic ecosystems.

“Given that we have all these introduced species already being considered as economically important and are being used in aquaculture, it is imperative that we focus our research and technology development on the breeding, propagation, and culture of our native species like Ayungin, Tawilis, Maliputo, Igat, and native Hito, both for conservation and sustainable aquaculture,” explains Dr. Ma. Rowena Eguia, a geneticist from SEAFDEC/AQD, an international body that promotes sustainable fisheries development in Southeast Asia.

Best Alternatives, an NGO based in the Philippines, and VB Consultancy, a research firm based in Europe, are working to highlight the dangers of farming invasive species. Instead of farming potentially invasive foreign Fish, the two groups are working to convince governments and private institutions to farm native species instead.

“In addition to conserving genetic diversity, farming native Fish has many benefits,” explains Jonah van Beijnen, head of VB Consultancy. “They are often best suited to local climates, giving them better chances of surviving adverse weather effects like storms or droughts. Local species can better resist both disease and parasites. Lastly, they are typically in demand and fetch better prices than invasive Fish.”

Institutions like SEAFDEC/AQD, DA-BFAR, DANFRDI, and the University of the Philippines are already experimenting with rearing and farming Ayungin, Tawilis, Maliputo, and other native Fish.

This is a vital step in protecting and sustainable managing the populations of native Fish still thriving in our country’s rivers and lakes.

Biodiversity – once lost – is gone forever. Though the Marikina River and other waterways of the Philippines still have many species today, there might soon come a time when our beautiful native Fish are relegated to the memories of those who used to visit our rivers.