Threatened fishes of the world: Onychostoma alticorpus (Oshima, 1920) (Cyprinidae)
The conservation status, species identification, distribution, specific habitat and ecology of a threatened, endemic cyprinid fish, Onychostoma alticorpus (Oshima 1919) is reported herein. It is merely found in five river basins of Taiwan. The protection of natural habitat would be very essential.
KeywordsOnychostomaCritically endangeredCyprinidaeFreshwater fishConservationTaiwan
Commonnames: Deep-body shovel-jaw carp; Kao-Shen-Ku-Yu (Mandarin); Shar-Ven (Taiwanese). Conservation status: Critically endangered (Ministry of Interior), endangered (IUCN). Identification: D 3 + 8; V 1 + 8; A 3 + 5; LL 43–44; PreD 13–15. Body oval, snout rounded, mouth subterminal, two tiny barbels, upper lip thick, prominent, lower lip with a horizontal shovel margin. Dorsal unbranched rays without serration. Body grayish silver dorsally; silver white ventrally. Dorsal, anal and caudal fins pinkish. Size 15–30 cm (SL), maximum 50 cm (Oshima 1920; Shen 1993; Chen and Fang 1999). Distribution: Endemic in middle reaches of the Kao-Ping, Hua-Lien, Shiu-Ku-Luan, Pei-Nan, and Tai-Mar-Li Rivers (Tzeng 1986; Chen and Chang 2005). Abundance: Adults/100 m2, 35–50, in the densest populations. Habitat and ecology: Prefers weak alkaline water(pH 8.0–8.8) with high DO(>70%), depth(0.5–7 m), moderate temp (19–24°C), clear water(0–50 NTU) and moderate flow(20–100 cm∙s−1), around 30–800 m altitude. Adult ascending migration during floods (May to August); descending movement is in September to February. Feeds diurnally on periphyton mainly, Bacillariophycae (Fang et al. 1995; Han et al. 2000). Reproduction: Larvae (1–3 cm) appears after rainy season, October to February at low altitudes, 100–350 m (Chen and Fang 1994; Fang et al. 1996). Threats: Habitat destruction from road construction, damage of natural vegetation and heavy silt; occasional illegal fishing by poison and electro-fishing; dam construction blocked seasonal fish migration; and water pollution (Chen 2001). Conservation action: Natural protective areas established in three basins have significantly improved for fish populations. Conservation recommendation: Prohibit damage of natural vegetation and river habitat, prohibit illegal fishing and avoid new dam construction. Remarks: The recovery of fish populations suggests the ranking of ‘endangered’ instead of ‘critically endangered’ in recent years. However, more field work on population dynamics may be necessary for further re-evaluation. Varicorhinus alticorpus is a synonym for Onychostoma alticorpus (Chen and Chang 2005).