New record of Sumatran barb (Puntigrus tetrazona) as an introduced species in Lake Toba, Indonesia: Invasiveness risk

Abstract

Lake Toba is an important habitat for native Indonesian fish species, but in recent years it has experienced pressure due to invasive introduced fish species. Introduced fish species that have been identified include Amphilophus labiatus, Aplocheilus panchax, Cyprinus carpio, Mystacoleucus marginatus, M. padangensis, Oreochromis mossambicus, O. niloticus, and Parambassis siamensis, while a newly recorded species has been discovered, namely Puntigrus tetrazona. Therefore, data are needed regarding the distribution, density, growth pattern, and risk of invasiveness of this species in Lake Toba as a basis for future management. This research uses an exploratory method. The frequency index value of P. tetrazona reached 70%, where absences were found in three locations, namely Ajibata, Silalahi, and Tongging. Population density values show that P. tetrazona has average value reaching 0.08 ind./m2, where the highest density was found in Muara reaching 0.39 ind./m2. The results of the Fish Invasiveness Screening Test (FIST) analysis showed that P. tetrazona was within the moderate risk category for the biodiversity of Lake Toba with frequency distribution (FD) values reaching 50%. The results of the length-weight relationship analysis of P. tetrazona showed a value of 3.027 (isometric growth pattern). The relative weight (Wr) condition factor showed a value of 102.96, which indicates a stable condition. The growth pattern values indicate that Lake Toba is a suitable habitat for P. tetrazona. Available food sources and a low level of competition are beneficial for P. tetrazona in this new habitat. The moderate risk posed by P. tetrazona to biodiversity in Lake Toba could possibly turn into a high risk if the P. tetrazona population is not controlled. Moreover, if the species that are natural enemies of this fish do not yet exist in Lake Toba, then in the next few years the population of P. tetrazona could experience an explosion. This will add pressure and threats to the survival of native fish species in Lake Toba, namely the Neolissochilus and Tor groups. The results of this research are useful for managing the population of P. tetrazona as a newly recorded species in Lake Toba, North Sumatra, Indonesia