The idea of a fish with “fingers” describes animals with uniquely adapted fins that function like hands. While not true fingers, these fins allow them to interact with their environment in ways other fish cannot. This adaptation appears in modern species that crawl on the seabed and in ancient fossils that mark a key transition in life’s history.
The Modern “Fish with Fingers”: Handfish
The contemporary fish known for these limb-like fins are handfish, a group of 14 species from the family Brachionichthyidae. Found in the coastal waters of southern Australia and Tasmania, their modified pectoral fins support their body weight. This allows these small fish to “walk” across the seafloor instead of swimming.
As bottom-dwellers, this walking movement is an adaptation for hunting slow-moving prey like crustaceans and mollusks. Their skin is covered in tooth-like scales called denticles, giving some a warty texture. Examples include the Spotted Handfish (Brachionichthys hirsutus) and the Red Handfish (Thymichthys politus), one of the rarest fish in the world.
An Ancient Ancestor with Limbs: Tiktaalik
Long before handfish, the ancient Tiktaalik roseae marked a key step in limb evolution. This 375-million-year-old fossil fish from Arctic Canada is a transitional form between fish and four-legged land animals. It had fish-like gills, scales, and fins, but also a flattened, crocodile-like skull and a mobile neck.
The bone structure within Tiktaalik’s front fins contained a skeleton similar to the arm and hand bones of land vertebrates, including a humerus, ulna, and radius. This structure allowed Tiktaalik to prop itself up in shallow water, an important development for the move onto land. Its fossils show how fins evolved into the limbs used by amphibians, reptiles, and mammals.
Conservation Concerns for Walking Fish
The future of walking fish is precarious, as many handfish species are critically endangered, including the Spotted, Red, and Ziebell’s Handfish. Their limited geographic distribution and low dispersal rates make them susceptible to environmental changes. Primary threats include habitat degradation from coastal development, pollution, and siltation in their estuaries.
Invasive species like the Northern Pacific seastar also pose a danger by preying on handfish eggs and the sea squirts they use for spawning. Conservation efforts include captive breeding programs, habitat restoration, and developing artificial spawning habitats. These provide safe places for handfish to lay eggs where natural sites are gone.