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Hi Cynthia,
Some remarks after the mail from Bill Allison about Perca flavescens
mortalities.
I heard about European perch (Perca fluviatilis) mortality during
commercial fisheries, in lake Geneva if I am right. It was claimed that
specimens died when they felt encircled by nets, i.e. before to be meshed.
That would mean a strong physiological shock like a heart attack because of
a single nervous stress.
This observation seems to be specific for lake populations, that means for
fish living in large shoals in quite open standing waters that probably
develop a strong inter individual sensitivity (strong group reactivity).
Perch collected in rivers do not seem to suffer such excessive reactions.
When I was young, I remember how hard it was to keep alive a perch angled
in lake while there were much less problems with those angled in rivers.
However, I was able to carry in quite simple vessels (i.e. unconfortable
conditions) during many days and hundreds of kilometers some specimens of
lake perch when they have been kept quiet during several days after catch.
Thus, I suppose that, after a while in captivity, they adapted, reduced
their stress and became able to suffer any new trial.
A more professional remark: psychological sensitivity apart, among European
species, Perch is one of the most sensitive to electric shock, i.e. it can
be easily killed by electricity if we do not care (too much intensity or
too long exposure, or, the worst, AC current use), but, if they recover the
initial shock, no delayed mortality is observed in riverine fish.
I do not know whether it exists relevant papers about these statments.
Hoping that might nevertheless help you,
Henri,
Henri PERSAT
Freshwater and Large River Ecology Laboratory
ESA CNRS 5023 - Universite Lyon 1
43, Bvd du 11 Novembre 1918
69622 VILLEURBANNE Cedex, France
Tel (33) 04 72 44 84 35
Fax (33) 04 72 43 11 41
E.mail [log in to unmask]
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