Balston's Pygmy Perch

Nannatherina balstoni is a small freshwater fish, the sole member of its genus, typically reaching only a few centimetres in length. It displays the characteristic laterally compressed body of pygmy perches, with colouration ranging from olive to dark brown and often a mottled pattern that provides camouflage among submerged vegetation and leaf litter. It feeds primarily on small invertebrates and plays a role in local freshwater food webs as both predator of aquatic insects and prey for larger fish and birds.

Breeding occurs in association with seasonal flow patterns, with eggs laid among aquatic plants.

The species is restricted to the southwestern corner of Western Australia, inhabiting permanent rivers, streams, and other inland wetlands, as well as some coastal freshwater systems. It favours slow-flowing, vegetated waters with stable conditions and reasonable water quality.

Populations are declining due to a combination of pressures. Dams, weirs, and water extraction have altered natural flow regimes and fragmented habitat, isolating populations and reducing available breeding sites. Invasive fish species compete with and prey upon it, while introduced predators and pathogens add further strain.

Habitat alteration, including changes to hydrology and vegetation cover, has degraded remaining refuges. Logging in catchment areas contributes to sedimentation and altered water quality, compounding these effects.

Conservation efforts include habitat protection within parts of its range, monitoring of remaining populations, and research into its ecological requirements to guide water management decisions. Some populations occur within protected areas, offering partial refuge from broader landscape pressures.

Given ongoing habitat fragmentation, water management conflicts, and invasive species pressure, the species' population trend remains decreasing, and its long-term persistence depends on continued habitat protection and management of freshwater resources across its limited range.