- An investigation of the fishes of the Willamette River and three of its larger tributaries was made during July, August, September, and November of 1951, to ascertain the possibility of using them as bio-indices of pollution. Thirteen stations were established on the Willamette River and tributaries. These stations were selected in respect to the major tributaries, cities, and sources of pollution. Two stations were located on the McKenzie river; two on the North Fork of the Santiam River; eight on the
main stem of the Willamette River from above Eugene to Oregon City; and one on the Clackamas River. Fishes were collected at each station by means of a seine. The fishes were preserved in a 10 percent formalin solution and returned to Corvallis where they were classified as to species and the numbers of each recorded. Stomach analysis were performed on a portion of the fishes collected from each of the stations. In an attempt to determine the affect of pollution on the fishes of an area, the samples from a clean-water station were compared with those
taken from a polluted station. From this survey a tentative list of fishes which were sensitive, intermediate and tolerant to pollution was formed. In general, the trout, salmon, whitefishes and sculpins were found to be sensitive; falcate dace, white crappie, smallmouth black bass, mountain suckers, and longnosed dace were intermediate; and redsided shiner, blacksided dace, coarse-scaled sucker, three-spined stickle back, squawfish, bullhead catfish, chiselmouth, largemouth black bass, Columbia River chub, and larvae of the Pacific lamprey were tolerant. It was found that even the most tolerant fishes disappeared when pollution was excessive. In addition to the biological data collected at each station, certain chemical and physical tests were also determined. Air and water temperatures were taken, along with hydrogen-ion concentration (pH), and dissolved oxygen content of the water. Bio-chemical oxygen demand (B.O.D.)
readings were taken at some of the stations by the Oregon State Sanitary Authority. River flow measurements were obtained from U.S.G.S. records for the gage at Salem, Oregon. The physical and chemical tests were used in conjunction with the biological findings to determine the condition of each station. Water flow data was used to determine low water periods. Chemical, physical and water flow data are shown in table form as well as graphically. The numbers of each species of fish and the food organisms found by stomach analysis are listed for each monthly sample and these data are also shown in table form.
According to observations from this survey there was a definite indication that pollution can be detected by using the species, numbers and stomach contents of fishes from a waterway.