• Swarno Lumbangaol, a tourism master’s graduate, returned to his hometown of Bakkara Village after 20 years of teaching in Aceh, North Sumatra, to continue his family’s fish farming tradition.
• He now focuses on cultivating a rare species of mahseer fish, called Ihan (Neolissochilus thienemann), which is endemic to Lake Toba and has a declining population.
• Swarno’s efforts in preserving Ihan have been supported by the Fisheries Department, and he has showcased his conservation work at the North Sumatra Fair attended by President Joko Widodo.
• In addition to fish farming, Swarno also cultivates Azolla (Mosquito ferns), an aquatic plant used to feed the fish, and aims to preserve the cultural significance of Ihan in Batak rituals and traditions.

Preserving Lake Toba’s Unique Ecosystem

Swarno Lumbangaol, a master’s graduate in tourism from a private university in Medan, North Sumatra, has returned home to preserve the cultural and environmental heritage of Lake Toba. After spending over 20 years as an educator in the cities of Meulaboh and Nagan Raya, Aceh province, North Sumatra. Swarno chose to come back to his hometown, Bakkara Village, with a mission to continue his family’s traditional fish farming practices.

Swarno wanted to continue his family’s tradition of fish farming in ponds. In the past, his grandfather raised carp, and his father raised tilapia and mujair (another type of tilapia) in the pond beside their house.

Swarno chose to cultivate a species of mahseer, called Ihan (Neolissochilus thienemann), which is ray-finned fish belonging to the Cyrpinidae (carp) family. Ihan is endemic to Lake Toba and is becoming increasingly rare due to environmental disturbances.

Swarno sources the Ihan fry from rivers around Humbang Hasundutan and Samosir. With three levels of ponds established on his property, Swarno makes use of Bakkara’s natural water sources and rocky terrain to create an ideal environment for the fish.

The Fisheries Department has recognized Swarno’s efforts in conserving Ihan and has supported his initiatives. Swarno introduced the unique fish at the North Sumatra Fair in Humbang Hasundutan, an event organized by the Ministry of Tourism and attended by President Joko Widodo.

In addition to cultivating Ihan, Swarno cultivates Azolla (Mosquito Ferns), an aquatic plant that serves as a food source for the fish. Azolla is a type of fern that floats on water. It is commonly found in flooded areas or rice fields, with a size of 1.5-2.5 centimetres. The small leaves overlap each other, with a greenish-red surface. Swarno also works as a local tour guide in his spare time.

About the Ihan Fish

Ihan is a protected species with full conservation status, according to the Indonesian Ministry of Marine Affairs and Fisheries’ Decree No. 1/2021.

The Indonesian Institute of Sciences (LIPI) describes Ihan as having a long, flattened body with a silvery colour. Ihan fish swim against strong river currents, resulting in a dense bone texture. The fish can also be characterised by 10 scales in front of the dorsal fin and 26 scales along the lateral line.

The endemic fish is classified as vulnerable by the International Union for the Conservation of Nature (IUCN) and shows a decreasing population trend, with only 5,000-10,000 individuals remaining.

Similar fish of the genus Tor and N. Sumatranus can be found within Lake Toba, but their populations are also declining. Fish within the genus Tor are known locally as ‘Jurung’ (mahseer in English).

‘There are indeed similarities between Ihan and other mahseer fish, but the difference lies in the shape of the lower snout and the eyes,’ said Swarno.

Preserving Toba Batak Culture

In local Batak culture, Ihan holds significant traditional value and plays a crucial role in sacred rituals. Historically, the fish was a delicacy for the kings of ancient Batak kingdoms and was offered to God (Mula Jadi Na Bolon) during traditional ceremonies. Another name for the fish in local Batak Ethnic language is  ‘Ihan Batak’ or ‘Ikan Dewa’ (Gods fish).

The Ihan fish is believed to bring blessings of good health, prosperity, and many descendants. In Batak weddings, an Ihan dish is given to the bride’s family as a reciprocal offering to seek divine blessings, known as “tudu-tudu sipanganon”.

Ihan is cooked in a distinctive way during Batak traditional ceremonies. The dish, called ‘Arsik’, consists of traditional Batak flavours including torch ginger fruit (asam cikala) and andaliman (which only grows in the Batak highlands).

The traditional dish is gradually disappearing due to the rarity of Ihan. Another species of carp, introduced by the Dutch during the colonial period, is replacing the Ihan fish in many ceremonies.

Swarno Lumbangaol’s dedication to preserving Ihan highlights the intersection of cultural heritage and environmental conservation. His efforts contribute significantly to the conservation of Lake Toba’s unique ecosystem and the revival of traditional Batak practices.

To learn more about conservation efforts and support initiatives like Swarno Lumbangaol’s, visit Hariara Institute’s website and explore how you can contribute to preserving Lake Toba’s natural and cultural heritage.

Written by Charlotte Gresham

• Lake Toba was formed from the caldera of an ancient volcano, which last erupted about 74,000 years ago. The eruption spanned thousands of kilometers, from the Indian subcontinent to southern China.
• Lake Toba holds a wealth of biodiversity, from the rare Batak fish (Neollissochilus thienemannie) to the horn-nosed lizard (Harpesaurus modiglianii Vinciguerra), which was recently rediscovered after 130 years.
• Myths and legends about Lake Toba also thrive among the local community. These stories personify the creation of Lake Toba and Samosire island in the lakes centre.
• Environmental degradation around Lake Toba has prompted the designation of the Toba Caldera area as a Global Geopark, which has been established since 2020. Management challenges are now a focus for stakeholders.

A Brief History of Lake Toba 

Lake Toba, the largest volcanic lake in Southeast Asia, sits at an altitude of 900 meters above sea level in North Sumatra. Covering an area of 1,130 square kilometres, the lake stretches approximately 100 kilometres in length and 30 kilometres in width, with depths reaching up to 508 meters.

The ancient Toba volcano erupted around 74,000 years ago, in one of the largest known supervolcanic eruptions (Petraglia & Korisettar, 2011). The volcanic ash covered vast areas, from the Arabian Sea to southern China, making it even more powerful than the Tambora or Krakatoa eruptions.

The impact of the Toba eruption extends beyond geology. Paleoanthropologists, archaeologists, and geneticists study its effects on human evolution and the distribution of Homo sapiens. This period also saw humans coexisting with other species such as Neanderthals, Denisovans, and Homo floresiensis. The eruption’s climatic impact may have even influenced the decline of various Homo species.

The existence of Toba as an ancient volcano was first revealed by Dutch geologist Reinout Willem van Bemmelen in 1939. His research found pumice stones around Lake Toba and rhyolitic ash dating back to the same period as Toba’s rocks in Malaysia and India. Further research by Craig Alan Chesner and John Westgate in the 1990’s confirmed that Toba’s ash spread worldwide.

Biodiversity of Lake Toba

Lake Toba’s unique geology fosters rich biodiversity. The endangered Batak fish (Neollissochilus thienemannie) is native to the lake and its rivers, breeding in clear water sources. In 2021, the government listed this fish as a protected species due to its alarming population decline.

The Lake also holds a rich diversity of amphibian species, including the horn-nosed lizard (Harpesaurus modiglianii Vinciguerra) which was rediscovered in 2020 after being declared extinct in 1891.

Additionally, Andaliman (Zanthoxylum acanthopodium), a spice endemic to North Sumatra and commonly used in Batak cuisine, thrives in the high-altitude regions surrounding the lake.

Cultural Heritage and Legends

Several ethnic groups live around Lake Toba, including the Batak Toba, Karo, Simalungun, and Pakpak. Their culture emphasizes togetherness and openness to newcomers, reflected in their welcoming greetings: “Horas Jala Gabe” (Toba), “Mejuah-juah Kita Kerena” (Karo), and “Njuah Juah” (Pakpak).

Local legends add to the lake’s mystique. One story tells of a man named Toba who married a beautiful girl named Putri, who was a fish cursed by a god. They had a son together, who was named Samosir. When Toba revealed Putri’s secret, she and Samosir disappeared. The legend says that Toba’s tears formed Lake Toba with Samosir Island in its centre.

Environmental Degradation and Conservation of Lake Toba

Despite its ecological richness, Lake Toba faces threats from pollution, industrial waste, and invasive species. For example, the water hyacinth weed covers many parts of the lake due to its uncontrolled growth. Such challenges underpin the importance of conservation efforts to preserve the lake’s natural beauty and biodiversity.

The initiative to designate Lake Toba as a UNESCO Global Geopark began with concerns about environmental degradation from deforestation, pollution, industrial development, and mining. The Toba Caldera was officially recognized as a Global Geopark during the 209th Session of the UNESCO Executive Board in Paris, on July 7th 2020.

“Achieving UNESCO Global Geopark status is challenging,” explained geoscientist Jonathan Tarigan.

“First proposed in 2009, it required forming a dedicated team in 2013 and addressing issues like community empowerment and master planning before final approval in 2020,” Jonathon added.

The Toba Caldera Geopark integrates geodiversity, biodiversity, and cultural diversity. It encompasses 16 geological sites across six districts, including Sipisopiso, Tongging, Tuktuk Peninsula, Puncak Uludarat, Sibeabea, Pusuk Buhit, Samosir Island, Uluan Peninsula, Hutaginjang, Bakkara Bay, and Tipang Valley.

To qualify as a Global Geopark, an area must meet global geological standards and focus on three pillars: local community empowerment, education, and conservation.”The development of the Toba Caldera Geopark is not solely about tourism but encompasses various aspects,” Tarigan concluded.

The Future of Lake Toba

Lake Toba is a natural wonder of immense geological, ecological, and cultural significance. Conservation efforts are crucial to preserving its unique biodiversity and heritage. Supporting these initiatives helps to protect Lake Toba and preserve its beauty and history for future generations.

Join us in our mission to conserve Lake Toba. Your support can make a difference in protecting this incredible natural and cultural treasure. Visit our website to learn more about our conservation efforts and how you can help.

By Barita News Lumbanbatu and Charlotte Gresham

• The Ingul tree, integral to the Batak Toba community, is used for crafting traditional fishing boats “solu”, natural pesticides, and foundations for traditional houses.
• Declining fish populations and environmental issues around Lake Toba have reduced interest in fishing, shifted economic activities to fish farming and are threatening traditional boat-making practices.
• Modern construction materials and the designation of forests as state land are diminishing the economic value of Ingul wood.
• To address concerns about the disappearing Ingul tree, an Indigenous school in the Huta Lottung community was opened to preserve and pass on traditional knowledge and cultural practices.

Ingul Tree: A Cornerstone of Batak Toba Culture

The “Ingul” tree, also known as Suren (Toona sureni), is integral to the ethnic Batak Toba community’s life. This tree’s wood is used to make “solu”, traditional boats used for fishing on Lake Toba. The Ingul wood and leaves also serve as natural pesticides for the Toba people. The Karo people, another ethnic group, use Ingul wood to make furniture and musical instruments.

Ingul trees grow in many gardens around Lake Toba, often alongside candlenut, cocoa, and mango trees. They also provide shade for coffee plants and thrive at 600-1,200 metres above sea level, with an average temperature of 22 °C.

The Role of Ingul in Batak Toba Culture

Ingul wood is known for being strong and resistant to water and insects, making it perfect for crafting solu, the traditional fishing boats used on Lake Toba.

“I order this wood from Holbung Village, Somosir. The trees here are still too small to use for making solu.” explained Op. Adrian, Head of the Huta Lottung Indigenous Community in Muara, North Tapanuli, North Sumatra, at his home on Friday [05/04/2024].

Making solu takes skill and artistry. Op. Adrian can earn between 1-1.5 million Indonesian rupiah(Rp) for making one solu, while Ingul wood costs around Rp4-6 million per cubic meter, with a diameter of 30-40 cm.

However, the declining fish population in Lake Toba, combined with pollution and the introduction of invasive predator species like the Flowerhorn fish, has diminished local interest in fishing

“It’s not about the pay; people are just not interested in fishing. They prefer fish farming,” he said.

Ecological and Cultural Significance of Ingul

Ingul belongs to the Meliaceae family. It is a fast-growing tree that requires minimal care, reaching heights of 30-50 meters with a diameter of about 1 meter. According to a report by Liberina Kristina Ibo and Septiani Dian Arimukti (BRIN, 2019), the Toba ethnic group use Ingul wood and leaves as natural pesticides

Ingul wood is also used as the foundation for traditional Batak Toba houses, known as Ruma Bolon. The Karo people also utilize the robust wood to make furniture and musical instruments.

The Future of Ingul Tree

Technological advancements in construction have reduced the demand for Ingul wood in boat building and traditional house construction, which now often use modern materials.

“Today’s houses are easier to build with cement and stone,” said Op. Adrian.

Edward Siregar, the Head of PD AMAN (Indigenous Peoples Alliance of the Archipelago) North Tapanuli, added that Ingul trees can still be found in Muara’s forests. However, they are losing economic value as these areas are being claimed as state forests.

“This raises concerns about the loss of community income and the fading of local wisdom regarding the use of Ingul wood,” he explained in early April 2024.

In response to these challenges, Edward established the Indigenous School in the Huta Lottung Indigenous Community.

“The goal is to ensure that local wisdom, especially solu making and other traditions around Lake Toba, is preserved and passed on to future generations,” he stated.

By Barita News Lumbanbatu and Charlotte Gresham