AUKE BAY LABORATORY (ABL) (cont.)

Auke Creek Weir Studies

Operations at the Auke Creek Weir through September 2003 completed 214 consecutive days of weir activity. Most fish counts, except for coho salmon and cutthroat trout, decreased after August, which is typical for Auke Creek. Water levels were moderate throughout the month but did not interrupt weir activities; water temperatures were below average during September.

For 2003, a total of 3,239 sockeye salmon migrated upstream at Auke Creek through September. This is greater than the average annual return (2,500 fish) of wild sockeye over the last two decades at Auke Creek but still well below the 1963-1981 average (7,000 fish). The preliminary estimate of marine survival, based on smolt counts from the year 2000, is 25%. Scales were collected from several hundred adult sockeye as well as from late-run pink salmon but have not been processed.

Figure 4.  Pink salmon escapements by brood year at Auke Creek, 1967-68 and 1971-2003.

A total of 10,580 pink salmon were counted at the weir in 2003 (Fig. 4 above). There were no hatchery fish for the year. The average run of wild fish from 1967 to 2002 was 7,460; the average run of wild fish plus hatchery fish was 10,266. Most of the pink salmon (6,098) entered Auke Creek during August; 4,198 were counted in September (Fig. 5 below). The estimated year 2003 return of wild pink salmon, based on the number of fry counted at Auke Creek weir in 2002, is 7%.

Figure 5.  Proportion of the total pink salmon run returning in September at Auke Creek. The lines in each group of markers represent the average of each group.

A total of 1,578 chums passed through the weir in 2003. Based on run timing and numbers, most of these fish were probably strays from DIPAC remote site releases. Three chum salmon migrated into Auke Creek in September, including one on 29 September, the latest a chum has ever been observed there.

A total of 518 adult and 216 jack coho salmon were counted at the weir in September. This is below average for the total return of coho salmon to the creek, and one of the lowest counts of coho adults on record for Auke Creek; average adult return to Auke Creek is 732. However, the marine survival for returning jacks and adults combined is above average. Despite a 44% incidence of the nematode parasite Philonema in year 2002 smolts, the estimate of survival for coho smolts that left Auke Creek in 2002 is 25%; the average marine survival of Auke Creek coho salmon smolts is 23.9%. The coho run at Auke Creek can continue into October, and the total weir and fishery counts will not be known until the end of that month.

A total of 164 adult chinook salmon (larger than 250 mm) were counted at the weir in 2003. No minijacks were captured this year because there was no release of juveniles in Auke Bay. This was the one of the lowest counts of adult chinook at Auke Creek, and because chinook salmon stray into the creek and are not allowed to spawn in Auke Lake, was a welcome reduction from the 2002 return of 668; only 4 years have had lower numbers of chinook salmon at Auke Creek.

A total of 91 cutthroat trout were captured in the weir through September. These fish usually continue to migrate upstream through October. From 1997 to 2002, the average count of upstream migrant cutthroat trout was 268.

Dolly Varden were also captured going upstream in 2003. Through the end of September, 3,770 fish were caught and released upstream of the weir. These fish usually continue to migrate upstream through October. The average number of upstream migrant Dolly Varden from 1997 to 2002 was 4,610.

By Jerry Taylor.

AFSC Quarterly
Research Reports
July-Sept 2003