Perspectives on sustainable management of the Poso Lake (Indonesia) endemic ricefish, Oryzias nigrimas (Actinopterygii: Adrianichthyidae)

Abstract

Introduction: The endemic fishes of the ancient lakes of Sulawesi are under increasing threat. Objective: To evaluate the data and information available from a holistic management perspective and to formulate measures to conserve the endemic ricefish Oryzias nigrimas in Poso Lake, Indonesia. Methods: Collection of primary data from three stations around Lake Poso and literature study. Results: Threats to O. nigrimas include habitat degradation and loss, introduced alien species, and exploitation as a locally important food fish. Options to promote sustainable fisheries management include spatial and temporal limitations to minimise catch of gravid or brooding fish. Habitat protection should include measures to minimise impacts from activities which can reduce water quality and disturb or kill aquatic vegetation. Conclusion: Measures to prevent further O. nigrimas population decline are considered urgent and further research is recommended to fill identified knowledge gaps. Ex-situ conservation, including the development of captive breeding, could also contribute to a holistic O. nigrimas conservation strategy.

Traditional fishing gear for sarasin’s goby (Mugilogobius sarasinorum), endemic to lake Poso, Sulawesi, Indonesia

“…Both introduced species are of low-value locally. Furthermore, O. vittatus is considered invasive [12], such as in Lake Talaga, Lake Rano, and Lake Lindu, Central Sulawesi [8]. The total catch of 483 M. sarasinorum in this study comprised 140 males and 343 females.…”

“…Visibility could not be measured because it exceeded the water depth due to the high water clarity at the sampling locations. The waters tend to be clear and transparent, most likely due to the generally oligotrophic conditions [12] and because turbidity does not last long in the streams flowing into the lake [9,19]. The substrate at the study site was dominated by coarse sand, pebbles, and rounded stones, and aquatic plants were absent.…”

“…Geological, geographical and ecological isolation have caused the evolution of unique aquatic biota in Lake Poso [4]. The endemic fauna include several endemic fish species including Adrianichthys kruyti, A. oophorus, A. poptae A. roseni, Mugilogobius amadi, M. sarasinorum, Nomorhamphus celebensis, Oryzias nebulosus, O. nigrimas, and O. orthognathus [6][7][8][9][10][11][12].…”

“…In recent decades, the abundance of endemic fish populations has declined, due to similar threats to those faced by fish in many other lakes such as eutrophication, intensive fishing, invasive non-native species, and pollution [12,13]. One of the endemic fish affected was A. roseni; this fish was collected in September 1978, but until now there have been no further reports [7][8][9]12]. In addition, the status of Sarasin's goby M. sarasinorum in the International Union for Conservation of Nature (IUCN) Red List was changed from Vulnerable to Endangered in 2019 [8,9,14].…”

“…In 2013 Lake Poso was assessed as Key Biodiversity Area (KBA) by Burung Indonesia [14] and Participatory Conservation Planning (PCP) has been carried out in 4 villages (Meko, Salukaia, Owini, and Uranosari) since 2017 [17]. Clearly the conservation of endemic fish in Lake Poso is important, including through addressing identified threats such as pollution and the introduction of non-native (alien) invasive species [12]. Conservation actions have been implemented in the area, including raising public awareness and reducing the use of chemical herbicides and pesticides in the surrounding watershed [14].…”