It's their job to boat out to two fish wheels twice a day to count, tag, measure and take scale samples from the chinook and chum salmon caught in it while heading upstream from the Bering Sea to spawn.
(It; 's; their job) (the chinook and chum salmon; caught; in it; T:while heading upstream from the Bering Sea)
It the chinook and chum salmon
's caught
their job
in it T:while heading upstream from the Bering Sea