Cook's figures for the groups which were formerly listed under the Chilula and Whilkut were 800 and 1,300 making a total of 2,100. Kroeber's figures were 600 and 400 for a total of 1,000. The difference between Cook's figures and those given here is partly due to the fact that Cook took the group on the North Fork of the Mad to be Wiyot, whereas I have them as Whilkut. Also Cook made a reduction of a ninth in his Mad River estimates because of the poor environment there. I have not done this because the Mad River region does not seem to me noticeably poorer than that along Redwood Creek. ESTIMATES BASED ON FISH RESOURCES For the six tribes just discussed, the ethnographic notes at our disposal offer a means of estimating the population, but we have also another basis for our calculations. Fishery was the most important single factor in the California Athabascan economy, hence the fish resources of the region undoubtedly exerted a marked influence on population size. Therefore, before attempting to estimate the population of the remaining groups, for which we have scanty ethnographic information, I would like to present some data on the fish resources of the region. I have attempted to calculate the number of stream miles of fishing available and thereby to form some estimate of the economic basis of each of the groups. Most of my information comes from Mr. Almo J. Cordone, Junior Aquatic Biologist of the California Department of Fish and Game, who was kind enough to gather the relevant data from the records of that organization. I have not included material on the freshwater trout, which was apparently too scarce to be important, or on the lamprey eel, on which we do not have sufficient information, although it was of some importance, especially in the Eel River and its tributaries. The available stream miles of fishing may seem insufficient material on which to base estimates of fish resources and unquestionably it would be desirable to have some idea of the fish population per mile of stream in order to estimate the food value of the resources available to the people. On the other hand, this point may not be as crucial as it seems, for apparently the fish population was not a governing factor in the number of fish taken by the Indians. According to Rostlund (1952, p. 17), the aboriginal fishermen of California did not even approach overfishing. If this is so, then there must have been fish left uncaught even in the smaller salmon streams and it would therefore seem that one stream was nearly as good as another, if it carried salmon at all. An exception would be the Trinity River and its tributaries, the only streams in the Athabascan area with both spring and fall runs of salmon. In other streams there is only a fall run.