Abundance and Seasonal Spatial and Diel Distribution Patterns of Juvenile Salmonids Passing the Red Bluff Diversion Dam, Sacramento River. Final Report Red Bluff Research Pumping Plant Report Series. Volume 14

摘要

The objective of our juvenile monitoring program was to generate in-river estimates of passage of juvenile chinook salmon, Onchorhyncus tshawytscha, and rainbow trout, O. mykiss, emigrating past Red Bluff Diversion Dam (RBDD). These data were utilized by the Bureau of Reclamation (BOR) for their evaluation and assessment of the potential for entraining emigrating salmonids into experimental water lifts (pumps) at the Red Bluff Research Pumping Plant (RPP). Four distinct races or runs of chinook salmon were documented emigrating past RBDD based on length-at-date criteria. Length frequency distributions were bimodal for each race, but were more pronounced for late-fall and spring chinook. Diel patterns in abundance existed below RBDD in close proximity to the RPP. Relative abundance was greater for nocturnal periods (71-74 percent) than diurnal periods (26-29 percent), especially for pre-smolt/smolt sized juveniles. Differences in the horizontal distribution of juveniles existed as well. Relative abundance was greater in mid-channel habitats than for either river-margin. Juvenile chinook salmon were more abundant in the upper-water column than the lower-water column as evidenced by high relative capture of chinook salmon by rotary-screw traps, compared with low relative entrainment of chinook by RPP pumps. Also, relative entrainment of benthic fishes (lamprey ammocoetes and prickly sculpins) was greater for RPP pumps than relative capture by rotary-screw traps. For all chinook captured, 83.8 percent were fry (less than 46 mm FL) and 16.2 percent were pre-smolt/smolt sized (less than 45 mm FL) juveniles. Fall chinook were numerically dominant relative to the other races of chinook. On average, 87.7 percent of chinook captured were fall chinook versus 1.4, 8.6 and 2.3 percent for late-fall, winter and spring chinook, respectively.