Weather Loach

The weather loach (Misgurnus anguillicaudatus) is an elongated, eel-shaped freshwater fish in the family Cobitidae, native to East and Southeast Asia, including China, Korea, Japan, and parts of mainland Southeast Asia. Its common name comes from a well-documented behavior of becoming restless and active ahead of drops in barometric pressure associated with approaching storms, a sensitivity thought to be linked to specialized inner-ear or air-bladder mechanisms. The species is a facultative air-breather, tolerating low-oxygen, muddy water where few other fish survive. Weather loaches have been introduced outside their native range through the aquarium and pond trades and have established populations in parts of North America, Europe, and Australia.

Weather loaches are recognized by their long, eel-like, cylindrical body and small barbeled mouth.

• Elongated body with tiny embedded scales, giving a smooth, slippery appearance
• Base color mottled yellow-brown to olive-grey with irregular dark speckling or blotching along the flanks
• Five pairs of barbels surrounding a small, downturned mouth
• Low, continuous dorsal and anal fins set well back on the body
• Rounded, paddle-like tail fin
• Grows to 15-25 cm

Distinguished from true eels by its barbels and small scales; distinguished from selectively bred dojo/pond loach color morphs of the same species mainly by its mottled, natural coloration.

Weather loaches inhabit slow-moving or still freshwater across East and Southeast Asia, including rice paddies, ponds, ditches, marshes, and muddy-bottomed streams, from China and Korea through Japan and into parts of Vietnam. They favor soft, silty substrates into which they can burrow, and tolerate a wide temperature range from cool winters near freezing to warm summers above 28C. As facultative air-breathers, weather loaches can survive in stagnant, oxygen-poor water, including temporary pools and heavily silted agricultural ditches, by gulping air at the surface and absorbing oxygen through the gut. Introduced populations now occur in parts of North America, Europe, and Australia, often in similar muddy, low-flow habitats.

Weather loaches are bottom-dwelling, primarily nocturnal fish that burrow into soft substrate during the day and forage at night for small invertebrates, insect larvae, and organic detritus using their sensitive barbels. They are known for a distinctive behavior of becoming noticeably more active, including surface-darting and erratic swimming, ahead of falling barometric pressure associated with storms, which gave rise to their common name. As facultative air-breathers, they regularly gulp air at the surface. They are generally peaceful and tolerant of other species, sometimes loosely social in groups. Spawning occurs in shallow, vegetated water during warmer months, with adhesive eggs scattered among plants and no parental care afterward.