Resilience of Mystacoleucus padangensis: Rediscovery, growth patterns, and conservation strategies in Lake Toba, North Sumatra

¹ Department of Aquatic Resources Management, Faculty of Fisheries and Marine Sciences, IPB University, Campus IPB Dramaga, Bogor 16680, Indonesia
² Department of Marine Science and Technology, Faculty of Fisheries and Marine Sciences, IPB University, Campus IPB Dramaga, Bogor 16680, Indonesia
³ Observer of Lake Toba, Tarutung, 22411, Indonesia
⁴ Senior High School 1, Parmaksian, Toba, 22384 Indonesia
⁵ Eco-Marine & Freshwater Research Institute (EMFRI), Bogor, 16118, Indonesia

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Mystacoleucus padangensis was introduced to Lake Toba in 2003 and thrived as a key fishery species until 2013. However, between 2014 and 2016, its population declined drastically, likely due to overfishing and competition with the invasive glassfish (Parambassis siamensis), leading to its presumed extirpation. Surprisingly, our ichthyofauna surveys in April and December 2024 revealed the species’ persistence in the lake. Specimens were collected using cast nets and electrofishing in littoral zones and inlets, with individuals measuring 75–156 mm in length and weighing 3.78–39.48 g. The species was recorded in six of the seven regencies surrounding Lake Toba, with the highest catch per unit effort (CPUE) observed in the inlets of Toba and Simalungun regencies. The length-weight relationship followed an isometric growth pattern (W = 0.000005 L^3.1206, R² = 0.98), and the condition factor (K) across five size groups averaged 0.85–1.04. These findings indicate that M. padangensis could be rehabilitated as a fishery resource, supported by available habitat niches and phytoplankton- based food sources. Conservation strategies, including restocking programs, control of invasive alien species (e.g., Amphilophus citrinellus), and protection of critical inlet rivers, are recommended to restore this ecologically and economically important fish population.