Update Assessment of Sockeye Salmon Production from Babine Lake, British Columbia

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Abstract

Wood et al. (1998) provided the last formal assessment of sockeye production from Babine Lake using production data spanning the 1950-1996 return years (1950-1991 brood years). This update adds 14 more years to the data series (1950-2010 return years, 1950-2005 brood years) and provides an overview of the monitoring methods used to assess Babine Lake sockeye production.

Three distinct yet overlapped sockeye “runs” return to Babine Lake each year: early-timed, mid-timed, and late-timed. Babine Lake sockeye were enhanced in the late 1960’s, which saw spawning channels and flow controls established on two of the mid-timed Babine Lake spawning tributaries located at Pinkut Creek and Fulton River. Approximately 90% of all Skeena River sockeye are now from Babine Lake, and of these, an average 75% are enhanced fish from Pinkut Creek and Fulton River.

Skeena River sockeye returns (catch plus escapement) increased substantially after Babine Lake enhancement and continued to do so throughout the 1980’s and through most of the 1990’s as sockeye returns to Babine Lake increased. Since the early 2000’s, Skeena River sockeye returns have declined to lower levels coincident with a recent decline in Babine Lake production. Escapements to enhanced Pinkut Creek and Fulton River continue to exceed spawning requirements, even with the recent declines in total production. Escapements to the unenhanced late-runs exhibit a long-term declining trend which was not evident in the last assessment conducted in the mid 1990’s. Late-timed escapements have been much lower than historic in recent years. Escapements to the early-timed and mid-timed unenhanced runs have also been very low in recent years.

Fry production from Pinkut Creek and Fulton River continues to account for ~90% of fry and smolt recruitment to the Main Arm of Babine Lake; yet total fry recruitment to the Main Arm still appears to be below maximum rearing capacity. North Arm/Nilkitkwa Lake fry and smolt production was on a declining trend prior to cessation of the last brood year assessed, consistent with reduced numbers of late-run spawners.

It is currently unclear how freshwater and/or marine survival variation may be influencing recent Babine Lake brood year recruitment. Reduced adult returns the past decade could be due to fewer smolts leaving Babine Lake, fewer smolts surviving as adults in the ocean, or some combination of both. Several mechanisms affecting freshwater and marine survival have been proposed, but data are lacking to make a proper assessment. Future research may help address some of the concerns.