South American armoured sailfin catfish from family Loricariidae belong among very popular ornamental fish species. Moreover, certain taxa are very successful invaders introduced via human activities to new localities out of their native ranges. Two species, the vermiculated sailfin catfish (Pterygoplichthys disjunctivus) and the Amazon sailfin catfish (Pterygoplichthys pardalis) established self-sustaining populations in Indonesian wild including Sulawesi island. These populations are abundant and dominate above native ichthyofauna in some sites. Also, hybrids of both mentioned species were recorded. Local fishermen consider these fishes as pests due to damaging seine and cast nets by sharp hard fin rays. Body of armoured sailfin catfish is covered by sturdy “shell” formed from hard scales which named these taxa being “armoured”. For this reason, these catfishes are unpopular for human consumption and are partly used just as a feed for domesticated animals when overpopulated in water bodies.

Once armoured sailfin catfish invade new locality, establish new population, multiply and spread in vicinity, their eradication or effective mitigation is mostly impossible. Negative impacts on native biota and entire ecosystem are well-known: competition, food web alteration, increased turbidity due to burrowing behaviour and related bank erosion, and disturbing of foraging behaviour of big aquatic mammals such as manatees.

To identify potentially endangered Indonesian regions, the climate matching analysis was computed (Patoka et al. 2020). As a result of comparison of temperature between the native range and Indonesia, it was found that most of Sumatra, Java, southwestern Kalimantan, southern New Guinea and several small island and islets such as Lombok are suitable for establishing and spreading of the Amazon sailfin catfish while the vermiculated sailfin catfish is risky for eastern Java and south of New Guinea. In case of Sulawesi, the Amazon sailfin catfish is a high-risk species threatening native biota with a potential to establish new populations in vast majority of freshwater bodies while the vermiculated sailfin catfish was predicted to establish in southern part of the island.

The aforementioned findings are in line with field data. In entire Indonesia, there were found 18 populations of both mentioned species in the wild. In Sulawesi, just the Amazon sailfin catfish was recorded. Two populations of this species were found in tributaries of the Palu river in city of Biromaru and one population was found in Buaya lake. This catfish is very tolerant and adaptable to various conditions and is generally perceived being a “tough fellah” which can survive also a short-term desiccation. Moreover, the survival of hatchlings is high due to parental care. Even if the current Indonesian legislative framework bans the new imports of armoured sailfin catfish species, this regulation is ineffective and new introductions and spreading of mentioned invaders is probable. In case of aforementioned lake population, further spreading to Bla river and Sidenreng and Tempe lakes in the nearby area is expected. Furthermore, unintentional escapes from aquaculture facilities are likely. It is up to responsibility of each farmer and producer to mitigate risk of escapes and introductions which is strongly related to effective conservation of awesome and rich Sulawesian freshwater biota.

Dead specimen of Pterygoplichthys sp. in Lake Mahalona discovered during Sulawesi Keepers expedition, September 2022. © Martin Hauskrecht

Reference: Patoka, J., Takdir, M., Yonvitner, Aryadi, H., Jerikho, R., Nilawati, J., Tantu, F. Y., Bohatá, L., Aulia, A., Kamal, M. M., Wardiatno, Y., Petrtýl, M. (2020) Two species of illegal South American sailfin catfish of the genus Pterygoplichthys well-established in Indonesia. Knowledge and Management of Aquatic Ecosystems, 421: 28.

Jiří Patoka