Chinook salmon research on the Unuk River, 1994

Description

The distribution and abundance of large chinook salmon Oncorhynchus tshawytscha that returned to spawn in the Unuk River in 1994 were estimated by using radio telemetry and a mark-recapture experiment. Age, sex, and length compositions were estimated for the immigration, and juvenile chinook salmon from the 1992 and 1993 brood years were captured for coded wire tagging to enable estimation of future harvests. Set gillnets were used to capture 169 immigrant chinook salmon 660 mm in (mid-eye to fork) length during June and July, 1994. One hundred sixty-one (161) fish were marked with spaghetti tags and opercule punches, and 109 of these fish also had radio transmitters inserted into their stomachs; 94 of the fish with radio transmitters were tracked to spawning locations. An estimated 17.4% (SE = 4.2%) of the fish returned to Canada, and 82.6% (SE = 8.6%) spawned in U.S. tributaries and mainstem waters. During August, 313 chinook salmon 660 mm in length were captured at spawning sites and inspected for tags; 10 of these fish had been previously marked. A modified Petersen model (n1 = 161, n2 = 313, m2 = 10) estimated that 4,623 (SE = 1,266) chinook salmon 660 mm in length immigrated to the Unuk River in 1994. Peak survey counts in August totaled 711 large chinook, about 15% of the estimated inriver run. Age and length composition of the immigration was estimated using a combination of the gillnet and spawning ground samples to remove bias. An estimated 9% of the immigration were age 1.1, 13% age 1.2, 28% age 1.3, 46% age 1.4, and 2% age 1.5. During October 1993, 13,959 juveniles from the 1992 brood year were tagged with coded wire tags, and another 2,642 smolt from the 1992 brood were tagged in May of 1994. In October 1994, 20,542 fish from the 1993 brood year were tagged.

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