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Dear colleagues:
I am involved in a study of predation by outmigrating hatchery coho
smolts on wild fall chinook smolts and pre-smolts. One of the things
we're investigating is the proportion of coho that have recognizable
fall chinook or diagnostic fall chinook bones in their stomachs.
Unfortunately, the river we're working on has been above or near flood
stage all spring, and we're having a terrible time collecting coho
smolts. Neither back-back shocking nor boat shocking nor beach seining
have been at all effective. Does anyone have an idea how we might more
effectively sample outmigrating coho smolts in a raging river? Also,
has anyone ever heard of a coho outmigration "stalled" by abnormally
cool water temperatures occurring late in the spring? Previously,
virtually all coho smolts released in our system had entered the
Columbia by the second or third week in May. This release, however,
seems to be "hanging up" somewhere, even though it's late in the season
and flows are very high. Does the fact mean daily water temperatures
are 10-12 deg F cooler this year than they typically are explain this
lack of movement?
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