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Background and 3 Questions:
I am trying to understand the migratory behaviour of Pacific lamprey
(Lampetra tridentata). I am examining the inriver timing of adult Pacific
lamprey on the northcoast of British Columbia, Canada. I have found that the
runs are extremely contracted, with as much as 50% of the run moving through
in just a few days and 80% of run in one of the 4 months of the run. This
seems unusual for such a large watershed (20,000 sq. km) with numerous
tributaries and presumably several stocks. I have too few seasons'
replicates (3) to unequivocally attribute the peak movement to high tides,
dark nights or river discharge. Sjoberg (1980) mentions that L. fluviatilis
entry to rivers is dependent on dark nights and that this knowledge is
"old-established" (I assume this means well documented). Others have
commented that mean body size decreases through the run. My data shows
clearly that body size is not decreasing with progression of the run (with
reasonable power), suggesting we are seeing at least a few "stocks". Why do
they all come at the same time?
Does anyone have data or references that show:
1) similar contracted run timing of L. tridentata or for other anadromous
lamprey spp.;
2) environmental variables driving the timing of return to freshwater;
3) body size as a function of the progression of the run.
Please direct all response to me and I post a summary if warranted.
Thanks.
Sjöberg, K. 1980. Ecology of the European river lamprey (Lampetra
fluviatilis) in northern Sweden. Can. J. Fish. Aquat. Sci. 37:1974-1980.
********************************************************
Michael R. Link
Biologist
LGL Limited, environmental research associates
Sidney, B.C., Canada
V8L 3Y8
Phone: 250-656-0127
Fax: 250-655-4761
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