7122

• UCREFRP Catalog Number: 7122
• Author: Maxfield, G. H., R. H. Lander and K. L. Liscom
• Title: Survival, growth, and fecundity of hatchery-reared rainbow trout after exposure to pulsating direct current
• USFW Year: 1971
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

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MAXFIELD ET AL.-PULSATING DIRECT CURRENT EFFECT ON TROUT 551
on the day following fertilization, (2) at the
eyed stage, and (3) at hatching. At the eyed
stage, the eggs were siphoned from the basket,
"bumped" (mechanical shocking of the eggs
caused by free fall from the end of the siphon
into a pail of water), and transferred to trays,
after which infertile eggs were removed. After
hatching, fry losses for each lot were counted
and recorded as (1) mortalities, (2) cripples
or monsters, and (3) fry with blue sac disease.
When the fry in each lot had absorbed the
yolk sac and had begun to feed, they were
counted and released into labeled troughs for
test and control fish.
SURVIVAL AND GROWTH TO SPAWNING
Cumulative rates of survival for test and
control fish between the times of electroshock
and of preparation for spawning were similar.
For the 1952 year class the cumulative survival
percentages were 92.9 for test fish and 89.6
for controls (9 November 1954) ; for the 1953
year class the respective percentages were 90.1
and 84.0 (17 December 1955; see Table 2).
Electroshock did not affect survival of the test
fish to spawning time in either year class.
Likewise, the average sizes of test and
control fish at various times between 26-27
May 1953 (before electroshock) and prepara-
tion for spawning were also similar. Although
for the 1952 year class near spawning time
(9 November 1954) the average length and
weight of the test fish (392 mm; 721 g) were
slightly less than the values for the control fish
(405 mm; 833 g), the size relation was re-
versed for the 1953 year class (Table 3). On
19 December 1955, average length and weight
were slightly greater for the test fish (425
mm; 861 g) than for the control fish (419
mm; 820 g). Thus, electroshock had no con-
sistent effect on growth of the test fish in
either year class.
FECUNDITY
Average numbers of eggs of the test and
control females of each year class were com-
pared on each spawning date. For the 1952
year class, the average number of eggs pro.
duced per female was higher for test fish than
for control fish on seven of nine spawn-taking
dates (Table 4). The difference in average
fecundity between test and control females
ranged from -706 to 320 eggs. For the 1953
year class, the control females had higher
yields on four of seven spawn-taking dates
(Table 5). The difference in average fecundity
between test and control females ranged from
-60 to 267 eggs.
The rand average yield of eggs per female
was 1,839 for the test fish and 1,850 for
control fish for the 1952 year class and 2,025
for test fish and 2,030 for control fish for
the 1953 year class (Tables 4 and 5). Evi-
dently electroshock did not affect the fecundity
of the test females in either year class.
SURVIVAL OF EGGS AND FRY
Although percentage survival of test fish
was appreciably smaller than that of control
fish for-lots of eggs taken from the 1953 year
class An?two spawning dates (9 January and
23 January-see Table 5), the percentages for
test and control fish of the two year classes
were closely similar for lots of eggs taken on
most other dates (Tables 4 and 5).
The grand average percentage survival of
offspring of test and control lots to different
stages was as follows:
rcentage urv
Parent year class, and
stage of development TestPefish Csontroivall fish
1952
Eyed eggs 91.0 90.3
Hatched fry 89.4 892
Feeding fry 88.0 87.9
1953
Eyed eggs 92.8 90.8
Hatched fry 86.4 87.0
Feeding fry 75.2 80.3
Clearly, the percentage survival of the off.
spring to the feeding fry stage was not reduced
by electroshock of the parents.
SUMMARY
Electroshock of yearling and young-of-the-
year rainbow trout apparently had no effect
on their survival, growth, and fecundity nor
were the survival and development of their
offspring adversely affected.