7706

• UCREFRP Catalog Number: 7706
• Author: Mesa, M. G. and C. B. Schreck
• Title: Electrofishing mark-recapture and depletion methodologies evoke behavioral and physiological changes in cutthroat trout
• USFW Year: 1989
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

BEHAVIOR AND PHYSIOLOGY OF MARKED FISH
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FIGURE 4.-Mean feeding and aggression rates for socially ranked hatchery (panels at left) and wild cutthroat
trout (panels at right) before (pre) and for several hours after they were electroshocked, marked, and released in an
artificial stream. Vertical bars represent 1 SE.
increased at 6 h, and again returned to control
concentrations for the rest of the experiment. Plas-
ma cortisol concentration in fish receiving only a
single electroshock did not increase immediately
(Figure 5) but increased significantly 15 min after
shocking (data not shown), reached a peak at 1 h,
and then returned to control concentrations by 3
h. Plasma cortisol concentrations in shocked and
marked fish and in fish only shocked differed sig-
nificantly immediately after application of the
treatment and 6 h later.
Because average plasma lactic acid levels dif-
fered significantly between trials, we analyzed the
data independently. In both trials, lactic acid in-
creased significantly after electroshocking plus
marking and remained elevated for 1 h (Figure 6).
Concentrations returned to control levels by 3 h
posttreatment. Lactic acid changes in fish receiv-
ing only a single electroshock were similar to those
in fish that were both shocked and marked.
HATCHERY
DOMINANTS
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Multiple electroshocks: -Because there were no
differences in average plasma cortisol levels be-
tween multiple-electroshock trials, we pooled all
data for analysis. In fish receiving multiple elec-
troshocks, cortisol concentrations were signifi-
cantly elevated after the second and third shocks
(Figure 7). Cortisol levels peaked after the third
shock, returned to control levels 6 h after appli-
cation of the first shock, and increased again 24 h
later. Cortisol levels of fish receiving only a single
shock reached a peak at 0.5 h posttreatment and
returned to control levels by 6 h. Cortisol concen-
trations for fish receiving the 30-s handling stress
reached a peak at 0.5 h posttreatment and re-
turned to control levels by 3 h.
Because average plasma lactic acid concentra-
tions differed between trials, we analyzed the data
from each trial separately. In the first trial, lactate
increased rapidly and reached a peak immediately
after the third shock in fish that received multiple