Assessment of the Availability and Quality of Spring Chinook Holding and Spawning Habitat in the South Fork Nooksack River, 1986

摘要

Results of an interagency study of spring chinook spawning and holding habitat in the South Fork Nooksack River are presented. Holding habitat appeared adequate for present spring chinook populations. However, much habitat was of porr quality, lacking the water depths and woodydebris preferred as cover by sping chinook. Mean pool depth was 5.0 ft which is significantly less than preferred depths. Filling of pools with sediment was documented. Water temperatures were above levels preferred by spring chinook. They were typically above 65 degress F and exceeded 70 degrees F at multipled stations for sevendays. Shallow pool depths, lack of adequate cover and high water temperatures appeared to contribute to stress and mortality from poaching and predation. Almost three million ft. of useable spawning habitat capable of supporting an estimated 2889 spawning fish was inventories. Four percent of the spawning habitat was judged unuseable due to fine sediment embeddedness; howerver 37% was 25-50% embedded, and may become unuseable if sedimentation increases. Stream stability ratings for most reaches were unstable or moderately unstable. Redd disturbance due to stream channel instability appears to be the most significant cause of mortality in the intragravel stage of development. Considerable redd loss (37.5%) was documented in a winter with moderate storm flows.