HomeFish encyclopediaRay-finned fishesFlatfishesRighteye floundersButter sole Butter sole (Isopsetta isolepis) Scientific name: Isopsetta isolepis Lockington, 1880 The Butter sole (Isopsetta isolepis) is a marine fish of the family Pleuronectidae. Native range: Eastern Pacific, Bristol Bay in the southeastern Bering Sea and Amchitka Island (Aleutian Islands) to Ventura, California, USA. BiologyCommon in shallow water on soft, silty bottom. Moves into shallow water in summer and to deeper water in winter. Spawning adults exhibit north-south migrations. Feeds on chaetopod marine worms, young herring, shrimps, and sand dollars. A tasty food fish, sometimes marketed. Also used for mink food.Source: FishBase, licensed CC BY-NC 4.0. Species factsScientific nameIsopsetta isolepisFamilyPleuronectidae (Righteye flounders)OrderPleuronectiformes (Flatfishes)ClassActinopterygii (Ray-finned fishes)Maximum length55.0Depth range20–425 m (66–1394 ft)EnvironmentMarine; demersal; oceanodromous; depth range 20 - 425 mClimateTemperateDistributionEastern Pacific: Bristol Bay in the southeastern Bering Sea and Amchitka Island (Aleutian Islands) to Ventura, California, USA.Conservation status (IUCN)Not EvaluatedThreat to humansHarmlessUsesFisheries: minor commercial; gamefish: yesResilienceMedium, minimum population doubling time 1.4 - 4.4 years (K=0.26; tmax=11; tm=2) SourcesTaxonomy, distribution and biology data: FishBase (Froese, R. and D. Pauly, eds.), licensed CC BY-NC 4.0.Last updated 27 September 2026