Volume 196 - 1993 - Part 26 of 45

ICES mar. Sei. Symp., 196: 117-121. 1993
The measurement of muscle fatigue in walleye pollock
(Theragra chalcogramma) captured by trawl
Gang X u, Takafumi A rim oto, and Yoshihiro Inoue
Xu, G ., A rim oto, T ., and Inoue, Y. 1993. The measurem ent of muscle fatigue in
walleye pollock (Theragra chalcogramma) captured by trawl. - ICES mar. Sei. Symp.,
196: 117-121.
Walleye pollock ( Theragra chalcogramma) were captured by otter trawl in the fishing
grounds off Hokkaido, northern Japan. In order to investigate the muscle fatigue of a
fish in relation to its swimming ability during the capture process, samples of the dorsal
white muscle of captured fish with a mean fork length of 43 cm were taken on board
and the concentrations of lactic acid and ATP-related compounds (A D P, AM P, IMP)
were later determ ined in the laboratory. Lactic acid concentration ranged from 52 to
239 mg 100 g -1 wet muscle and A T P concentration from 0.13 to 1.57 //mol g _1 wet
muscle in the fish immediately after capture. Some of the fish had a higher ATP
concentration of about 1 /^mol g ~ 1with a lower lactic acid concentration of about 50 mg
100 g -1 , very similar to that observed in the fish after 24 h recovery in a 500 litre
holding tank. During a recovery period of 24 h, the A TP concentration did not
increase, but the concentration of ATP-related compounds such as A D P and AM P
increased gradually. The resuits suggest that some of the walleye pollock might not
have experienced complete muscle fatigue, and might be able to swim longer inside the
net, which was towed at speeds of 4.0 to 4.6 knots.
Gang X u: Fisheries and Marine Institute o f M emorial University o f Newfoundland, PO
Box 4920, St J o h n ’s, Newfoundland, Canada A I C 5R3; Takafum i A rim oto: Tokyo
University o f Fisheries, M inato-Ku, Tokyo, 108 Japan; Yoshihiro Inoue: National
Institute o f Fisheries Engineering, Kachidoki, Chuo-Ku, Tokyo, 104 Japan.
Introduction
Changes in carbohydrate metabolism in fish following
severe muscular exercise have been well reported in
relation to muscle fatigue (Beamish, 1966a, 1968; Prit­
chard et al., 1971; Johnston and Goldspink, 1973;Driedzic and Hochachka, 1976). In most fishes, the lateral
musculature consists of two main fibre types, usually
term ed red and white muscle. The red muscle is aerobi­
cally active by itself during swimming at sustained
speeds, whereas during burst swimming the white
muscle becomes active together with the red muscle.
The white muscle carries out anaerobic glycolytic
metabolism which results in glycogen depletion and
lactic acid accumulation (Bone, 1966). The glycogen in
white muscle is one of the major fuel sources supplying
the energy required during swimming. In the glycolytic
pathways, the formation of A TP, which serves as the
immediate source of energy for muscle contraction, is
the most important function. In view of the relationship
between energy supply and muscle contraction, studies
on the concentrations of muscle lactic acid and ATPrelated compounds may improve the understanding of
muscle fatigue in fish after strenuous exercise, such as
swimming inside towed fishing gears. Much of the older
literature in this area has been reviewed by Driedzic and
Hochachka (1978).
Walleye pollock ( Theragra chalcogramma) are fre­
quently captured by otter trawls in the offshore fishery of
northern Japan. Observations with an underw ater video
camera during the capture process have shown that most
of the fish were inactive, both in the net mouth and
inside the net, which was towed at about 3.8 knots
(Inoue et al., 1992). However, from the video record­
ings, it could not be determined whether the fish had
been exhausted by swimming along with the trawl at the
towing speed. In this study, a series of experiments were
carried out to determine the level of muscle fatigue in
captured walleye pollock.
117
Material and methods
All research tows were made by two 124 G .R .T . type
commercial trawlers RV “No. 85 Y awata-maru” during
27-28 July 1988 and RV “No. 67 Eishou-maru” during
24-25 July 1989, in the fishing ground off Kushiro on the
east coast of Hokkaido, Japan. The gear was towed
along depth contours ranging from 154 to 235 m. The
towing speed varied between 3.8 and 4.6 knots accord­
ing to sea conditions. The towing duration was between
50 and 180 min, depending on the num ber of fish inside
or around the net. Samples of walleye pollock were
taken at random about 2 min after the net was hauled
aboard at the end of each tow. In the 1988 trials, muscle
samples were taken from the fish immediately after
capture. In the 1989 trials, the fish were first sampled
from the catch immediately after capture and then
placed in an aerated 500 litre holding tank for recovery.
Muscle samples were then taken from the fish after
recovery periods of 0.3, 6, and 24 h (Table 1).
For analysis of both lactic acid and ATP-related
compounds, muscle samples (1 g) were cut from the
dorsal white muscle block above the anus of freshly
killed fish. The muscle pieces were then placed in a
scintillation vial with 5 ml of cold (0°C) perchloric acid
(PCA) solution (6%) to remove protein. A fter the
muscle pieces were homogenized in ice, the samples
were kept in a “Styrofoam” bag containing dry ice and
brought back to Tokyo University of Fisheries for bio­
chemical analyses. The mixture was filtered with a
0.45 ,um syringe filter and the filtrate was centrifuged at
3000 g for 8 min. The supernatant solution was stored at
—30°C until analysis. Lactic acid concentration was
determined colorimetrically by the method of Barker
and Summerson (1941). All readings were made at 560
nm in a spectrophotom eter (Hitachi, UV-1000). Lactic
acid concentration is expressed as milligrams of lactic
acid per 100 g wet muscle.
A T P and its related compounds, A D P , A M P, and
IMP, were determined by high-performance liquid
chromatography (HPLC), measuring UV absorption at
254 nm (Suwetja et al., 1989). A 5 /A PCA extract was
injected into a TSKgel O DS-80™ column (5 /jm, 4.6 X
150 mm, Tosoh) equilibrated with 3% m ethanol in
0.05M K2H P 0 4 buffer, pH 6.5 (PB). Elution was con­
ducted at a flow rate of 0.5 ml m in- 1 , first with a linear
gradient between 3% and 15% m ethanol in PB for 30 s,
then with 15% methanol in PB for 19.5 min. Identifi­
cation of ATP-related compounds was carried out by
comparing the retention time of peaks in H PL C between
the sample and standard compounds. A T P concen­
tration is expressed as micromoles A T P per 1 g wet
muscle, as are the A D P , A M P, and IMP concentrations.
All changes in lactic acid and ATP-related compounds
were tested for significance using Student’s t test.
Results
In the 1988 trial, sampling was carried out over a total of
five tows. Six to eight individuals were sampled for each
tow. For the fish immediately after capture, the concen­
tration levels of muscle lactic acid varied between 52 and
239 mg 100 g ' 1. From a total of 38 samples, 14 samples
had lactic acid concentrations that were under 100 mg
100 g ' 1. O n the other hand, muscle A T P concentrations
in the fish immediately after capture were relatively low.
With the exception of a few samples, most were under
the level of 1/^mol g“ 1 (Fig. 1). The mean values of lactic
acid and A TP concentrations for samples in each tow are
given in Table 2. Most of the fish immediately after
capture were characterized by a high lactic acid and low
A T P concentration in their white muscles. However,
some fish had a low lactic acid and high A T P concen­
tration. These conflicting results between individuals
and tows may be associated with differences in operating
conditions, or variations in fish exertion during the
capture process. However, we found no conclusive evi­
dence to explain the relationships quantitatively.
In 1989, measurem ents were carried out in fish after
different recovery periods. Fish were removed from the
holding tank and decapitated immediately. The mean
value of lactic acid concentration for five individuals
after 18 min recovery was 154.2 mg 100 g“ 1. This value
Table 1. Operating conditions of the fishing boats during the sea trials collecting the samples of walleye pollock for biochemical
analyses.
Tow
no.
1
2
3
4
5
6
7
8
118
Sample
date
Towing
period
(min)
Towing
depth
(m)
Towing
speed
(kt)
Fishing
method
27 Jul 1988
27 J u l 1988
27 Jul 1988
27 Jul 1988
27 Jul 1988
24 Jul 1989
25 Jul 1989
25 Jul 1989
130
50
180
125
125
135
85
78
163-215
205 - 2 3 5
195
190
185
205
165
154
4.6
4.0
4.2
4.5
4.1
3.8
4.5
4.3
Bottom trawl
Mid-water trawl
Bottom trawl
Bottom trawl
Bottom trawl
Bottom trawl
Bottom trawl
Bottom trawl
during the recovery process. A fter 24 h recovery, the
total free adenylate pool was restored to 12.15 ,Mmol g~ 1,
which was three times as much as that after 18 min
recovery. The energy charge, [(ATP) +0.5(A D P)]/
[(ATP) + (A D P) + (AMP)] as defined by Atkinson
(1968), was low at about 0.20 in all states of recovery
(Table 3).
30%
30%
n»38
n *3 8
20
20
10
10
0
0
0
100
L a c tic
200
0
300
a c id (mg/100g)
0.5
1. 0
1.5
A T P ((imol/g)
Discussion
Figure 1. Percent frequency distributions of concentrations of
muscle lactic acid and A TP in walleye pollock immediately
after capture in tows 1 to 5 (see Table 1).
was higher than that for the fish immediately after
capture (121.7 mg 100 g_1). A fter 6 h recovery, the lactic
acid concentration had not changed significantly
(P> 0.05), compared with that in the fish after 18 min
recovery. By contrast, the fish after 24 h recovery
showed a great reduction in lactic acid concentration
(Fig. 2). This mean value was 52.6 mg 100 g - 1, very close
to that in some fish with low lactic acid.
A TP concentration remained low and unchanged dur­
ing all recovery periods (Fig. 2). In addition to lactic acid
and A TP, measurements of A D P, A M P, and IMP were
also carried out to observe the total change in the free
adenylate pool. The concentrations of both A D P and
AM P in muscle increased, whereas IMP decreased as
the recovery period increased. The total free adenylate
pool [(ATP) + (A D P) + (AM P)j increased gradually
Many investigators have used lactic acid as a measure of
muscle fatigue in fish following exercise (Beamish,
1966a). For Atlantic cod (Gadus morhua) of about 40
cm length, white muscle lactic acid in the fish after
swimming at 130 cm s-1 for 30 min was higher (189 mg
100 g~*) than that in unexercised fish (66.8 mg 100 g-1 ).
Despite 4 h recovery, its lactic acid level was almost
unchanged and remained high (153.7 mg 100 g ~ ’). A fter
8 h recovery, the muscle lactic acid disappeared gradu­
ally to near unexercised levels (52.9 mg 100 g“ 1)
(Beamish, 1968). With reference to lactic acid concen­
tration in plaice Pleuronectes platessa L. immediately
after capture by otter trawl, a high level of 297-396 mg
100 g“ 1 in white muscle was observed (W ardle, 1978).
That muscle lactic acid in walleye pollock immediately
after capture was much higher than after 24 h recovery is
in accord with the observations of Beamish (1968) and
Wardle (1978). Based on absolute lactic acid values, it
seems likely that most of the walleye pollock captured by
otter trawl have experienced strenuous muscular exer­
s*
15, 10
200
■8
c
AMP
IMP
3
8.
£o
5
-3
E
ADP
ATP
< o
00.3
24
0 0.3
6
24
R ec ov ery p erio d (ho u rs)
Figure 2. Changes in muscle lactic acid and ATP-related compounds in walleye pollock after different recovery periods. Values
shown are means for five individuals (see text).
Table 2.
Mean values for muscle lactic acid and ATP-related compounds of walleye pollock immediately after capture by trawls.
Tow no.
1
2
3
4
5
Mean
No. of fish
Fork length
(cm)
Lactic acid
(mg/100 g)
ATP
(Mmol/g)
6
8
8
8
8
4 1 .7 ± 4 .r
45.1 ± 4.5
40.0±4.8
41.8+6.1
43.9±5.4
82.2 ± 16.0
140.3± 19.6
156.3+37.9
104.8±36.2
115.3±52.7
0.98±0.33
0.41 ±0.11
0.52±0.12
0.41 ±0.11
0.34±0.11
42.5±5.4
121.7±43.9
0.5110.27
a Standard errors (s.e.).
119
Table 3.
pollock.
Comparisons of the values of total free adenylate pool and energy charge after different recovery periods in walleye
Recovery period (h)
Metabolite
Adenylate pool (umol/g)a
Energy chargeb
No. of fish
0.3
6
24
5 -7
5 -7
4.74±0.63c
0.17±0.01
5.79±0.58
0.21 ±0.01
12.15±1.26
0.16±0.02
a (ATP) + (ADP) + (AMP).
b f(ATP) +0.5(ADP)]/[(ATP) + (ADP) + (AMP)].
cStandard errors (s.e.).
tion and become fatigued during the capture process.
However, in some of the walleye pollock, only lower
lactic acid levels, corresponding to that after 24 h recov­
ery, were detected. These fish are likely to have a
different level of muscle fatigue from that in most of the
fish caught by trawls.
With respect to changes in nucleotides, Jones and
Murray (1957) reported that in rested cod Gadus callarias, A TP concentration in muscle was 5.34 «mol g- 1 ,
and in exhausted cod which were caught by trawl, A TP
decreased to a low level of 0.26 «mol g_1, with a striking
increase in IMP. Usually the rate of utilization of ATP
for muscle action is related to its rate of production
through glycolytic metabolism. As the work load of the
tissue exceeds its aerobic capabilities, the 5'-A M P de­
aminase converts A M P to IMP, and the adenylate pool
is decreased, resulting in muscle A TP reduction (Driedzic and Hochachka, 1978). O ur observations in fish
immediately after capture showed that A TP concen­
trations in white muscle were low for most of the fish. In
contrast to the gradual disappearance of muscle lactic
acid following recovery, muscle A T P was not restored
significantly in any recovery period (P>0.05) (Fig. 2).
However, the obvious increase in the total free adeny­
late pool after recovery might account for some of the
muscular recovery from fatigue (Table 3). The changes
in the free adenylate pool were very similar to the
patterns between rested and exhausted fish observed by
Jones and Murray (1957) and Driedzic and Hochachka
(1978). On the other hand, the level of energy charge
was almost unchanged and remained low during recov­
ery periods. This fact may indicate that these fish had not
completely returned to an unexercised state even after
24 h recovery. It seems likely that slow muscular recov­
ery from fatigue might be associated with degree of
fatigue, as well as experimental conditions including
influences of engine noise and vessel vibration.
In the present study, the capture of walleye pollock
could have occurred at any time during the tow. It is hard
to assign qualitative figures to strength of exercise and
physical condition of fish (Beamish, 1966a). When fish
are able to detect trawl gears visually, they have been
observed to maintain station with the gear as it is towed.
When fish are unable to swim to keep up with the trawl.
120
they become exhausted and drop back into the codend
(Wardle, 1983). However, in the absence of vision, fish
can only react to a moving net by a startle reaction when
struck by the net (Glass and W ardle, 1989). Since our
trawls were towed in the deep sea at about 200 m, the
fish were estimated to recognize the trawl gear probably
with a low acuity in this dark environment (Zhang and
A rim oto, 1993). During the capture process video
recordings were taken to observe the behaviour of
walleye pollock at a water tem perature of 2°C, while
artificial light was provided by a halogen lamp of 150 W.
The video recordings showed that most of the walleye
pollock inside the net did not swim actively and drifted
passively towards the codend, even in the artificial light
condition (Inoue et a i , 1992). For G adidae of similar
size, it was found that at low tem peratures from 0 to 5°C,
Atlantic cod could only maintain endurance swimming
for several seconds at high speeds of above 2 m s_1
(Beamish, 1966b; He, 1991). For walleye pollock of 5053 cm length, the maximum swimming speed estimated
from muscle contraction at 5°C was 2 . 1 m s -1 (Arimoto
et al., 1991). H ere, if the walleye pollock swim to keep
up with the trawl at towing speeds of 4.0 to 4.6 knots (2.1
to 2.4 m s~ !), the fish would be exhausted to a great
extent after burst swimming for a short time. Wardle
(1983) suggested that the fish in the codend are exhaus­
ted to varying degrees by their efforts made during the
capture process. Therefore, some captured walleye pol­
lock with a lower lactic acid and higher A T P concen­
tration probably had not experienced complete muscle
fatigue during the capture process and could have swum
for longer. This result implies that inactive fish observed
with an underwater video camera might not have swum
long with the trawl at high speeds, and before becoming
completely exhausted most of them already dropped
into and struggled in the codend, while some were quiet
in the codend.
Acknow ledgem ents
We are grateful to D rs Takaaki Shirai, Ken Suzuki, and
Toshio H irano, professors of the D epartm ent of Food
Science and Technology of Tokyo University of Fish­
eries, for encouragement and valuable suggestions dur­
ing the course of this study. We thank M r Frank Chopin
for his kind inspection of the manuscript. Thanks are
also due to the captains and crew of RV “No. 85 Y awatam aru” and “No. 67 Eishou-maru” for their assistance
during the cruise.
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121