Since the late Pleistocene the Colorado River has periodically filled the Salton Basin of southern California to form a huge lake. Lake Cahuilla. Fish remains recovered from archaeological sites occupied about 500 years B.P. along the shores of the last highstand of this lake have been identified as razorback sucker. Xyrauchen texanus, Colorado squawfish. Ptychocheilus lucius, striped mul- let. Mugil cephalus, machete. Elops affinis, and bonytail. Gila elegans. For a number of reasons some of these identifications are considered tentative: the zoogeographic basis is doubtful iO. robusta, G. cypha, and the sucker Catostomus latipinnis may also have been present), ta.xonomic imprecision makes early range determinations unreliable, the remains are fragmentan.-. and individual variation and potential hybridization make definitive determinations challenging. Zooar- chaeologists need to be aware of and address these types of difficulties when they are encountered.