Whitefish populations around the world have long been difficult to categorize taxonomically. The whitefish of Bear Lake, Utah/Idaho are no exception. There are three recognized species of Prosopium that are endemic to the lake. Two of these species, Prosopium spilonotus and Prosopium abyssicota, have previously been indistinguishable outside of spawning times. Previous studies have proposed additional taxa within P. spi/onotus to further complicate the identification among these taxa.

Morphological characteristics were quantified on wild whitefish from Bear Lake, as well as from progeny reared in the laboratory from the wild adult fish. The purported taxa were separated in the field using the best characteristics presented in previous studies, and the progeny were reared separately in these groups. Otolith aging was also done on the wild adult fish to understand the age structure of the spawning populations.

Results from otolith aging and morphological analyses on the laboratory reared fish indicated that there is only one taxonomic group of P. spilonotus. By using scale counts, it was determined that P. spilonotus and P. abyssicola can be distinguished from each other with considerable reliability.