THE RELATIONSHIP BETWEEN RIVER FLOW AND ENTRY TO THE ABERDEENSHIRE-DEE BY RETURNING ADULT ATLANTIC SALMON

One hundred and nine returning adult salmon were radio-tagged in the e stuary of the Aberdeenshire Dee, Scotland between February and August 1985 to 1989 and the times when 62 fish entered the river were recorde d. Elapsed times between tagging and river entry were significantly gr eater during periods of lower than average river flows in all months w here there were sufficient data to allow statistical comparison. The d egree of association between river entry and particular levels of rive r discharge rate varied seasonally. The proportion of days associated with river entry declined at the lower end of the range of flows avail able to tagged fish in the summer months. Absolute levels of river dis charge played a significant role in modifying the response of salmon t o changing flows. During periods of lower than average seasonal flow, river entry was closely associated with days when Bow had increased si nce the previous day. During periods of higher than average Bow, river entry was not significantly associated with such periods of increased flow. The results suggest that models which relate river entry by sal mon to absolute discharge rates alone are unlikely to be generally rel iable.