Stage height of the Copper River was recorded at the Flag Point Channel East and West Bridge beginning May 12 and at the Million Dollar Bridge starting May 10. Throughout the sampling period, stage height was above 2.5 m at the Flag Point Channel and, with the exception of 11 May, about 40 m at the Million Dollar Bridge.

The acoustic system was operated at Flag Point Channel for a total of 567 h (98% of the time) from 0800 hours on 5 May to 0700 hours on 29 May. Counts were interrupted for a total of 11 h during the season.

A transducer pitch of -3.5 to -4 deg was maintained throughout the sampling period, yielding a counting range of 20m.

Visual review of target strength echograms showed very good separation of eulachon Thaleichthys pacificus and salmon. Displaying the echograms at very low thresholds (-65 dB and lower) revealed eulachon tracks but these were easily discerned from the much stronger tracks left by salmon. Angle echograms indicated little to no downstream movement of salmon.

Daily counts totaled 9,022 salmon for the period sampled (5 - 29 May), with a peak of 992 fish on 21 May. It took the field technicians app. 2 h to count a 24-h period. NVE and Aquacoustics staff checked a subsample of at least four 15-minute counts per day and provided feedback to the technicians within 24 hours. Validated counts were fowarded to NVE and ADF&G by 0900 hours each day.

Similar to 2001, 2002 and 2004, relative changes in acoustic counts at Flag Point Channel mirrored the trends in the counts generated by the Miles Lake sonar. The comparison of time series plots of acoustic counts with Miles Lake data lagged 1-day lag provided the best alignment of peaks and slopes of the Floag Point Channel and Miles Lake sonar counts. This alignment appears to stretch closer to a 2-day lag towards the final 2 days of the study period, which correlates with rising water levels. Further inspection of the time series using a 1-day lag suggested a distinct change in the ration between the Flag Point Channel and Miles Lake counts. The ration dropped from 10:1 prior to 21 May to 24:1 after May 23. On May 22, the ration was midway between the two periods.

The 3-day moving average of the Flag Point Channel acoustics catch efficiency (Flag Point Channel index per 1,000 fish counted at Miles Lake) was compared to data from 2002 and 2004. The efficiency of the Flag Point Channel started lower in 2005 than in 2002 and 2004, but ended at a similar ration to the other 2 years. In 2002 and 2005, a 1-day lag was applied to the Miles Lake data (considered to give the best fit), whereas a 2-day lag was used in 2004. Data from 2003 were not included in the comparison because Flag Point Channel acoustic data were poor due to the extremely low water level.

In 2005, as in the previous four years, daily acoustic indices at Flag Point Channel decreased 1-2 days after the start of each commericial fishing opening in the Copper River District, suggesting that salmon migrated from the fishery to Flag Point Channel in about 1-2 days.

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