Conservation ActionsConservation of this species does not exist. Conservation is urgently needed to save this species from extinction. Considering the unstable peace and order around Lake Lanao, a combination of ex-situ (offsite) and in-situ (onsite) conservation approaches under community-based resource management with active participation of the 19 local government units surrounding the lake is highly recommended.
A comprehensive biodiversity assessment in the lake is imperative. Extensive and intensive surveys are urgently needed to locate surviving individuals of this species. More specifically, a thorough survey in the southern part of the lake to verify the presence of this species is needed. A species recovery program should be immediately launched. A comprehensive information and education campaign program should be developed and implemented to increase public awareness and generate public participation for high species recovery. Breeding and stock enhancement programs are highly recommended to restock the lake. Eradication programs of invasive species in Lake Lanao should be a priority. A strategic regular water quality survey and monitoring are needed to identify and reduce or eliminate pollution hotspots.
Location InformationBarbodes sirang is endemic to a single location in Lake Lanao, Lanao del Sur, Mindanao, Philippines. Lake Lanao is the largest lake in Mindanao and the second largest lake in the Philippines. Together with its only outlet (Agus River), it serves as a major source of hydroelectric power, supplying the majority of the electricity needs of the entire Mindanao (Escudero 1995, Rosagaron 2001, Naga 2010, UPLB-DENR 2014). The lake has a maximum depth of 112 m, a mean depth of 60.3 m, a replacement time of 6.5 years, a lake surface altitude of 702 m, and a surface area of 357 km2 (Frey 1969). The estimated extent of occurrence (EOO) of this species is 441 km2 and the area of occupancy (AOO) is 358 km2.
Population InformationThe estimate of the population of Barbodes sirang is inferred from the changes in catch statistics. Historical catch data in 1970s, 1980s, and 1990s clearly showed the gradual decline of the fisheries production of B. sirang (Sanguila et al. 1975, Escudero et al. 1980, Escudero and Demoral 1983, Escudero 1995). In 1974 and 1976-1977, this species was the most abundant species with 49% (approximately 424 MT/yr) and 55% (approximately 412 MT/yr) contribution to the fisheries production, respectively (Escudero et al. 1980). In 1982-1983, its fisheries production for a year decreased significantly, representing only 17% (92.019 MT/yr) of the total catch (Escudero and Demoral 1983). In 1990-1991 survey, sampling months were not indicated but it is assumed that it is likely for a year of monitoring just like in the 1982-1983 survey of Escudero and Demoral (1983). Fisheries production in 1990-1991 declined, constituting only 9% (22.442 MT/yr) of the total fisheries production in Lake Lanao (Escudero 1995). In a span of 17 years, this represents over 90% reduction in fisheries catch data. After the 1990-1991 survey, no major surveys were conducted in Lake Lanao until mid-2000s due to unstable peace and order around Lake Lano and lack of research funding. In November 2007, approximately 100 individuals were obtained from the markets for fecundity analysis (Mangondato 2008). In 2008 (Ismail 2014) and in 2015 (DENR 2015), direct field sampling, market survey and fish landing monitoring did not find this species. In May 2016-March 2017, this species was not also encountered after about a year of fish landed catch monitoring conducted every other day in major fish landing sites representing northwestern, northeastern, southwestern and southeastern parts of Lake Lanao (Torres 2018). Local knowledge through Key Informant Interviews was also sought to supplement data from these fish landing surveys. Most key local fishermen, fish vendors and housewives confirmed the disappearance of this species in the lake and fish markets for many years. Some claimed that this species is already very rare. A fisherman captured this species in 2006. Another fisherman reported that he caught one piece of B. sirang in 2015. A wife claimed that she saw the species in the market in 2016. These results imply that B. sirang is very rare but may still survive in Lake Lanao.
ThreatsThe survival of this species is mainly threatened by the invasive alien species, Giuris margaritaceus (Eleotridae), a native species in the Philippines but translocated accidentally in Lake Lanao. The pathway of introduction of G. margaritaceus into the lake was probably through the stocking of fingerlings of Nile Tilapia (Oreochromis niloticus) coming from a government hatchery (Guerrero 2001). This invasive species was estimated to have been introduced in the lake in the early 1970s and eventually occupied the entire littoral portion of Lake Lanao (Escudero 1995). Another invasive species that has contributed to the population reduction of this species is Glossogobius giuris (Gobiidae). The pathway of this predator goby to enter Lake Lanao was by unintentional introduction probably through the stocking program of milkfish (Chanos chanos) aimed to increase fish production in 1960 (Juliano et al. 1989). The growing abundance of these two invasive species has corresponded with the gradual disappearance of endemic cyprinids in Lake Lanao. Notably, G. margaritaceus has become the most abundant fish throughout the lake since the early 1980s. Its increasing contribution to the lake fisheries has coincided with the decreasing catch of all other fishes, outnumbering the endemic, native, and other introduced fish species. Both G. margaritaceus and G. giuris fed on fishes (Sanguila et al 1975, Escudero et al. 1980, Escudero and Demoral 1983, Escudero 1995). Glossogobius giuris was found in the stomachs of sirang (Sanguila et al. 1975). Giuris margaritaceus was described as a voracious feeder, devouring almost anything and feeding on organisms that usually live in the littoral zone, where endemic cyprinids inhabit (Escudero and Demoral 1983). It fed on fishes at all stages (Escudero and Demoral 1983, Escudero 1995).Other issues in Lake Lanao that have posed threats to the survival of this species include overexploitation, rampant use of destructive fishing methods, particularly dynamite fishing when it was still in abundance, unsustainable fishing practices, extraction of water from the lake for industrial, agricultural and domestic uses, illegal logging, and pollution (Torres 2018, Metillo and Garcia-Hansel 2016, Ismail et al. 2014, Naga 2010, Guerrero 2001, Rosagaron 2001, Escudero 1995, Bleher 1994, Kornfield and Carpenter 1984, Escudero et al. 1980, Sanguila et al. 1975).
Both G. margaritaceus and G. giuris feed on fishes (Sanguila et al. 1975, Escudero et al. 1980, Escudero and Demoral 1983, Escudero 1995). Giuris margaritaceus was described as a voracious feeder, devouring almost anything and feeding on organisms that usually live in the littoral zone, where endemic cyprinids inhabit (Escudero and Demoral 1983). It feeds on fishes at all stages (Escudero and Demoral 1983, Escudero 1995).