LENGTH AND WEIGHT OF THE GIANT MIOCENE SABERTOOTH SALMON, ONCORHYNCHUS RASTROSUS FROM WASHINGTON, OREGON, AND CALIFORNIA

Sabertooth Salmon bones are found in Late Miocene marine and freshwater sediments from coastal California and Oregon and inland deposits near the Columbia, Klamath, and Sacramento rivers. Oncorhynchus rastrosus, a relative of Sockeye, Chum, and Pink Salmon, evidently migrated up large rivers to spawn and complete its 4-7 year life cycle. Oncorhynchus rastrosus is known to have been a planktivore, based on its lack of feeding teeth and its fine, closely-spaced gill-rakers for straining plankton. Complete fossil specimens are unknown. Bones in fossil collections of the University of Oregon and the Los Angeles County Museum provide measurements that allow estimates of body size of the fish. Lengths were estimated from head and vertebral measurements. Weights were estimated from regressions and allometric equations relating weight to length of large salmon specimens. Vertebrae were most useful as the basis for length: the largest vertebrae of O. rastrosus were 28 mm long and 60 mm in diameter. Conservatively assuming 60 salmon vertebrae plus head and tail lengths, the maximum total length was estimated to be 7.9 feet (2.4 meters). Standard allometric equations relating weight to length of Alaskan Chinook (King) Salmon estimate the weight of a 7.9-foot salmon to be 375 lbs (170 kg). That length is 1.6 times as long as the largest recorded Chinook Salmon. The Sabertooth Salmon weight is 2.9 times the maximum weight of the largest Chinook Salmon. Projections based on larger potential girths of spawning Sabertooth Salmon, as captured in Ray Troll's expert drawings, paintings, and models, suggest that weights of around 500 pounds were possible. Available specimens suggest that the average length was probably around 5-7 feet (1.5-2 meters). Growth rates over 4-7 years were somewhat less than those of planktivorous whale sharks and basking sharks. The estimated growth is consistent with accepted models of Late Miocene upwelling and high primary productivity in the northeast Pacific.