52 
BUI.I.ETIN OF THE BUREAU OF FISHERIES. 
Pajaro fauna, but other species besides, and also because it is many times larger, and 
in the opinion of geologists it is considerably older. 
In a recent study of the topography of a district including part of the Pajaro basin, 
Dr. J. C. Branner® discovered unmistakable evidences of a former shifting of the channel 
of Coyote Creek, a stream of the Sacramento drainage basin, whereby its upper portion 
was for a time transferred to the Pajaro drainage. Coyote Creek drains the upper 
(southern) part of Santa Clara Valley, which is prolonged for a considerable distance 
southward as the San Benito Valley, the two being separated by a low divide which 
crosses obliquely from the southeast to the northwest. The Coyote has its origin in the 
mountainous district south of Mount Hamilton and has attained considerable size when 
it breaks from the range through a narrow gorge to enter the valley from the east. It 
passes near the divide just mentioned, turns abruptly northward and continues its 
course directly to San Francisco Bay. On the southwest side of the divide Llagas 
Creek emerges from the mountains to the west, enters the valley and flows southward 
to the Pajaro. The relative positions of these streams are shown on the map, plate xrx. 
Speaking of Coyote Creek, Dr. Branner says: 
From the mouth of the gorge where this creek debouches on the plain a great alluvial fan spreads 
out toward the south and west across the entire width of the Santa Clara Valley, at this place a distance 
of 2 ) 4 : miles. This fan forms the watershed in the valley trough between the Bay of San Francisco and 
the Pajaro River or the Bay of Monterey. & The configuration of the materials of the alluvial fan at the 
mouth of the gorge shows that the Coyote has been shifting its channel of late. A terrace south of the 
stream, and approximately parallel with it, shows that it formerly flowed toward the west, while another 
and still higher terrace farther south shows that at an earlier date it flowed toward the southwest; and 
the general form of the alluvial fan shows that the whole fan was built by the Coyote. It is a character- 
istic feature of streams, in the building up of such deposits, that they swing from side to side, flowing 
down over their own deposits in every direction, and shifting their channels as they become choked up 
by the deposit of their excess of load. The depth and position of the channel through which the Coyote 
now flows after emerging from the hills show that there has been no recent discharge of its waters toward 
the Pajaro. The general topography of the region about the mouth of the gorge suggests that the alluvial 
fan was built up a long while ago, and at a period when the stream was much more active than it now is — 
possibly during or toward the close of the glacial epoch. During the glacial epoch the streams of the 
region were much more vigorous than they have been since, for the coast stood at an elevation of two 
thousand or more feet higher than it does at present. There was therefore a greater precipitation, and 
during tlie winter months the Mount Hamilton Range must have been covered with snow which accumu- 
lated more than it does now and went off rather suddenly with the warm rains of early spring, producing 
much greater floods than we now have. It follows from the form of the alluvial fan on the plain where 
the stream emerges from the mountains that the Coyote must have shifted from side to side in the usual 
fashion, especially in the early history of the alluvial cone and during the constructive period. It flowed 
sometimes toward the northwest, draining into the Bay of San Francisco, and at other times toward the 
southeast, draining through the Pajaro into the Bay of Monterey. 
The fishes of the Coyote are like those of the Sacramento, the stream itself being a 
part of the Sacramento system, the salt water of San Francisco Bay not being a constant 
barrier to the free passage of fishes from stream to stream along its shores. If a portion 
“ Branner, J. C.: A drainage peculiarity of the Santa Clara Valley affecting fresh-water faunas. Journal of Geology, vol. xv, 
1907, no. I, p. i-io, fig. 
This alluvial fan is indicated by dotted lines on the map, plate xix. 
