Thayeria boehlkei

Thayeria boehlkei, the blackline penguinfish, is a species of freshwater ray-finned fish belonging to the family Acestrorhamphidae, the American characins. This species is endemic to the Amazon River basin and Araguaia River, in Peru and Brazil respectively. The species is popular with aquarium hobbyists, and is traded under a variety of common names including blackline penguinfish, blackline thayeria, hockey-stick tetra, penguin fish and penguin tetra.

The fish is named in honor of James E. Böhlke (1930–1982) of the Academy of Natural Sciences of Philadelphia, because of his interest in and contributions to the knowledge of South American characids.