Hanford Reach Fall Chinook





        Researchers are developing a model to describe the spawning habits


of fall chinook in the Hanford Reach of the Columbia River.  The model shows


much more spawning habitat available than is used by these fish.  Fall


chinook are very concentrated into narrow bands along certain reaches of the


river.   Based on the model, less than 25 per cent of the available spawning


habitat is used.





        The fall chinook spawners choose spawning habitat that is influenced


by upwelling of water in the spawning gravel.  The source of this water is


from the river itself and not ground water. 





        The patchy distribution of spawning is related to upwelling of river


water in certain areas of the river.  This water enters the gravel substrate


at the head of bars and comes out along the margins of the bar further down


river.  This subgravel flow of river water is warmer than the main flow of


the river.





        The subgravel water increases the oxygen flow over the eggs and the


warmer water shortens the incubation time and probably protects the eggs


from anchor ice during the late fall and winter months prior to hatching.





       This research, funded by the Bonneville Power Administration on


Columbia Basin wild salmon populations, was presented for review by


scientists at the Columbia Basin Fish and Wildlife Authority Project Review


held in Portland, Oregon on March 25, 1997.