Rheocles derhami

Rheocles derhami is a small freshwater fish endemic to Madagascar, belonging to the family Bedotiidae. This species is found exclusively in the island's freshwater river systems, where it inhabits flowing waters with rocky substrates. The species exhibits the characteristic elongated body form typical of rheotactic fishes, adapted for life in current-dominated environments.

Rheocles derhami faces severe threats primarily from habitat degradation and loss due to deforestation, agricultural expansion, and sedimentation of waterways. The conversion of native forest to agricultural land has resulted in increased erosion and altered water chemistry in the streams where this species occurs. Additionally, the introduction of non-native fish species poses a significant threat through competition and predation pressure.

Water extraction for irrigation and domestic use has further reduced available habitat by lowering water levels and altering flow patterns. The species' restricted range makes it particularly vulnerable to environmental changes, as local extinctions cannot be compensated by recolonization from other areas. Conservation efforts for Rheocles derhami are limited but include habitat protection initiatives within Madagascar's protected area network.

Research programs focus on better understanding the species' ecological requirements and population status. Community-based conservation approaches are being developed to engage local stakeholders in watershed protection activities that benefit both the species and local communities dependent on freshwater resources.

This species inhabits flowing freshwater streams and rivers in Madagascar with rocky substrates and clear water. It requires well-oxygenated waters with moderate to strong currents typical of upland river systems.