Embed Size (px)
Citation preview
CgT," 'S
FISHERIES AND MARINE SERVICE
Translation Series No. 4320
An outline of the management of salmon hatching and rearing
Anonymous
Original title: Sake no fuka, shiiku kanri yoryo
From: (Supervised by:) Hokkaido Salmon Hatchery Fishery Agency of Japan, (9): 1-43, 1976
Translated by the Translation Bureau (ELC) Multilingual Services Division
Department of the Secretary of State of Canada
Department of Fisheries and the Environment Fisheries and Marine Service
Vancouver, B. C.
1978
FISHERIES AND MARINE SERVICE
Translation Series No. 4320
An outline of the management of salmon hatching and rearing
Anonymous
Original title: Sake no fuka, shiiku kanri yoryo
From: (Supervised by:) Hokkaido Salmon Hatchery Fishery Agency of Japan, (9): 1-43, 1976
Translated by the Translation Bureau (ELC) Multilingual Services Division
Department of the Secretary of State of Canada
Department of Fisheries and the Environment Fisheries and Marine Service
Vancouver, B. C.
1978
-1 -
TABLE OF CONTENTS
CATCHING ADULT FISH
Catching Adult Salmon Trout 1 Locating the Place for Catching Fish 1 The Methods of Catching Adult Fish
Weirs 2 Seines 2
The Fishway-Type of Fish Catching 3 Others 3
CATCHING INSTALLATIONS 4
HOLDING ADULT FISH
Holding Adult Fish for Egg Collection 15 Types of Holding Facilities
Fish Tanks 15
Double Stop 15 Holding Ponds on Land 15 Holding Ponds in the River 16
Important Items in the Establishment of Holding Facilities Short-Period Holding 16 Long-Term Holding 16
Advice on Holding Management 17
THE COLLECTION OF EGGS AND SPERM
The selection of Adult Fish 20 Killing the Ripe Adult Fish 20 Transfer of the Fish Used for Egg Collection 21 Egg Collection 21 Sperm Collection 22 Fertilization 22 Water Absorption and Washing 23
TRANSPORT OF EGGS
Transport Directly After Fertilization 24 Transport in the Eyed Stage 25
EGG STORAGE 26
CALCULATION OF THE NUMBER OF EGGS 28
EGG MANAGEMENT
The Influence of Light on Eggs 30 Conditions in the Incubation Water 30 The Quantity of Water Inflow 31 The Degree-Total and Number of Days to Hatching 33 The Disinfection of Eggs and Removal of Dead Eggs 34
Page
Page
EGG MANAGEMENT (cont'd.)
REFERENCE MATERIAL (No. 1) • The Controlled-Flow Siphon Method of Egg Disinfection . . 36 . The Preparation of thé Stock Solution -
in the Siphon Bottle › 36
MANAGEMENT DURING THE HATCHING PERIOD 38
MANAGEMENT OF THE FRY Environmental Conditions in the Fry Pond
The Surfacing Pond . 39 The Rearing Pond . . . . ..... . . . . . 39
Management of the Hatchlings 40 Feeding and Rearing of Fry 42 REFERENCE MATERIAL (No. 2)
The Proper Method of Measuring Water Temperature . . . 43 The Release of Fry 44
THE CONDITION OF THE INCUBATING AND REARING WATER
The Hydrogen Ion Concentration (pH) 46 Dissolved Oxygen (0.0.) . . . . . . . . . . .... . 46 Chemical Oxygen Demand (C 0 D ) 47 Ammonia' Nitrogen (NH 2 -N) . . . . . . . . . . . . .... . 47 Iron (Fe) 47 Transparency, Suspended Solids (S.S.) . . . ... . 48 The Silica (Si0 2 ) to Calcium (Ca) Ratio . . . . ... . 48
REFERENCE MATERIAL (No. 3)
Salmon and Trout which Ascend Rivers in Hokkaido' Sake Chum Salmon (Oncorhynchus keta) (WALBAUM) .... 48
Karafutomasu Pink Salmon (Oncorhyhchus gorbucha) (WALBAUM) . 49
Masumosuke .Chinook Salmon (Oncorhynchus tschawytscha) (WALBAUM) 49.
Sakuramasu . . . •,- • Cherry Salmon (Oncorhynchu's masou) (BREVOORT) 50
CATCHING ADULT FISH
1. Catching Adult Salmon and Trout
As the first step in the artificial rearing of salmon and
trout, the catching of adult fish in rivers is completely and essen-
tially different from ordinary fishing. These fish ascend rivers for
the purpose of reproduction over a very wide time range, and the
method of capture must be very carefully considered.
2. Locating the Place for Catching Adult Fish
The season and the circumstances in which the adult fish
ascend a river depend on the position, morphology, and structure of
the river, on the current speed and on the location of the spawning
places. These conditions must therefore be separately investigated
in each river.
(1) The location should be easily accessible, and should be a place
where there are mature adults in large numbers. Locations close
to natural spawning places are ideal, but many of them are
otherwise difficult.
(2) The number of fish ascending a river is often greatly diminished
before arrival at the spawning place by natural conditions in
the river, by natural enemies and by man-made obstacles. It is
therefore often logical to establish. a catching place close to
the river mouth. However, since in the early part of the season
there will be many fish in such a location which are not yet
ripe, the establishment of facilities for a long period of hold-
ing becomes unavoidable.
(3) Furthermore, it is necessary to select a location where catching
installations, holding installations and operating installations
can be unified, and where there will be good traffic facilities
for the transport of eggs.
-2 —
(4) If the catching place is established near the river mouth, the
necessary dykes and holding facilities will be of large scale,
and they will also be easily susceptible to flooding. The site
selection therefore requires considerable care.
3. The Methods of Catching Adult Fish The methods used for catching depend on the size and shape
of the river, the location of the catching place and the conditions
of river banks and the river bed. The method which results in the
least damage and fatigue of the fish must be used.
(1) Weirs (traps)
(a) In one method, the fish are intercepted by a lattice of
wood, bamboo, iron or vinyl chloride built across the river,
with catching tanks inserted at some positions, and the fish
which have entered a catching tank are scooped out by means
of a net.
(h) Weirs may offer high resistance to the flow of water,
particularly during floods, and may frequently be damaged
or may cause a structural damage to the river banks. This
may be avoided by the use of floating upper ends which are
held by wires instead of being fixed, so that during floods
they are below the surface and have little resistance.
(c) The structure of the weir, and the number and position of
the catching tanks, must be decided after , careful consider-ation of the mutes used by the adult salmon or trout.
(d) Where there is much depth but the velocity is low, the whole
structure may be of fish netting, but this is limited to
places with special conditions.
(2) Seines
Seines can be used in places where there are large
concentrations of adult fish, and where the river bed conditions
are suitable, but large seines and personnel skilled in their use
are required.
ri
„ _
- 3 -
Moreover, fish are frequently damaged when caught with
seines, so such methods should be confined to places where the
use of other methods would be difficult.
(3) The Fishway-Type of Fish Catching
In a method often used in America, the holding pond is
connected to the river by a fishway to induce the fish to enter
the holding pond by themselves, and since the fish are not touched
by hand, this is a very good method.
Various configurations are possible, and the type must
be chosen which is best suited to the relations between the hold-
ing pond and the river. The building of a fence, a weir or a
dyke across the river, towards the entrance to the fishway, is
very effective in catching the fish ascending the whole of the
current.
This method increases the cost of the facility, but has
the advantage that no work force is required for its further oper-
ation and management.
(4) Others
Gill nets, drift net, gaffs and hooks may be used, but
since they cause damage to the adult fish, they should be used
only as auxiliary tools when the water temperature is low and the
movements of the fish become sluggish, or when the fish are so
ripe that they can spawn immediately.
MEMO*.
* Throughout the text, there are blank spaces left, marked MEMO, evidently intended for readers' additions. These have been indicated, but no such spaces left, in the translation. Translator.
•
CATCHING INSTALLATIONS (reference materials)
Type of Construction Method Construction Details
Basic construction Preparation of the The river bed is to be prepared so as to equalize the water pressure all river bed along the weir installation.
River dyke Cutting or piling As directed by the supervisor, the earth removed in cutting away or rais- construction earth for the dyke ing the river dyke is to be carried away and not dumped into the river.
The gabions (rock-filled bamboo baskets for embankments) are to be placed firmly and carefully so as to make foundations which will not collapse.
Dyke construction Follow the plan. The rocks chosen for the foundations must be good with gabions quality, hard material which TAdll not weather away, and must be larger
than the basket mesh. The embankment must rise to a height above the river which will not fail to protect it, and the gabions are to be con- nected together with 12-gauge wire. The construction is to follow the plans, with 2 gabions in each metre placed perpendicular to the river bank and with the rocks well tamped and pressed together.
Weir installation Foundations in The gabions join those in the dyke. Faggots of raw willow wood are to be and construction the river bed used. The gabions are jointed by gauge 12 wire. When sunken gabion con-
struction is used, the construction is • to be such that the water level and the current path are not changed.
- Pile driving The main piles are to be debarked oak logs placed vertically. The ends are sharpened, and they are driven in to a depth determined by the super-visor according to circumstances and the difficulty of driving. The interval between the piles is 1.8 m (one old Japanese "ken").
- Prevention of Each main pile is to be tightly bolted to the bracing. vibration of main piles (bracing)
Cross-bars holding To be of pine lumber of dimensions according to the plans. the grating
L
CATCHING INSTALLATIONS (cont'd.)
Type of Construction Method Construction Details
Grating The upper slats, the middle slats and the vertical slats are to be of first-quality pine lumber. The spaces between the slats are to be 3 cm. To hold the slats, 6 cm nails are to be driven into the cross-bars. They are to be spaced at 2-1/2 times the thickness of the slats.
Construction of Methods of Proceed as shown in the plans. The installation of the tank must conform catching tanks construction to the natural instinctive movement of the adult salmon and trout, so it
is to be placed according to instructions from the supervisor.
Miscellaneous Materials All materials for this installation must be sampled and inspected by the supervisor before being used.
Cleaning up When the construction of this installation is completed, all temporary facilities are to be removed from the site. All remaining material such as wooden boards is to be dug up and removed according to the instruction from the supervisor, and the site is to be left clean and free of debris.
,
Catching Tank Beam 9cm Wee
- 6 -
PLAN VIEW
Catching Tank
e—a—o--e—n---eg--0-0—e—e—e—e—ci-----e-- -é „, g
1 V Weir Stake Locations 5 -= i
k- 4 m---1 • 1---4.-,
m
SIMting
X
\\\
I_ Mil ■ TIMO W222 _fx
1.2 -r
12m
C cinema 24mm Mt
CATCHING INSTALLATION EQUIPMENT
I
.4.— . . \ I .\-20cmx15enm
I I
\s"--- 3cenx3an
CATCHING EQUIPMENT Fish Holder
Itt3 .95 —t3
J-5 55
Splint /31:xx x 13ernx 1.65m
nut attd bett rith weer Manna..
30ernx12mm
PLAN VIEW • 1/20
mullicrn Craesbeom (square lumber) 10.5cm x 10.5 cm
Upper 3cm x 3cm
spocinq 2.8fflt
LI _ tr—rPsate 3franx10.5amx40rdn
nut and bolt 7AatA x but
012 Wks
CATCHING EQUIPMENT hoe
•■■1 9 •■■•
LSpHnt 10amnlm
Sow Twigs I5cms5m
Main Piles 105 aex 4m
SIDE VIEW S. 1/ 20
Upper eats 15 1^
JObrnItIbrnm
7.=
boit 21eroxerom
4,* G
I.9cm I3cm
MAIN CATCHING EQUIPMENT he
(simplified type)
- 10 -
PLAN and CROSS-SECTIONAL VIEWS S. 1/10
_ 1 t ! I
. so eiïecca 0: ._. _ . _ • _ - I_ _ __.,
_ _
=,------ .i II . g = .. i 1
..% No 7
No.6 14 4.
FRONT VIEV/ Loser Slotting Lattice and Bose S.1/5
flL 1.4
DESIGN of CATCHING EQUIPMENT for a catching location
1.1„.
ss_
#10 Gablon f-45emx4m
à A ...04 • fev 7 0 Mt ffe
;
'...•■••••■••••■■■•••••■■•••••
#14 Wire----)
- 11 -
PLAN VIEW
MAIN CATCHING EQUIPMENT
CATCHING INSTALLATIONS - LIST OF MATERIALS*
Total From To Nomen- Quality Number Last Next
No. Clature and Size Units Needed Year Year Purpose
1 Pine 2.7 m x 3 mm piece 2400 For a total river width of 144 m, 2400 pieces are lumber x3 mm used for the lower gratings. 25 pieces form one
sheet of 1.8 m.
2 Oak 1.80 m long piece 320 Strengthening pieces for the above pine lumber lumber 4.5 mm x grating (No. 1).
3 mm
3 Bamboo Pieces piece 3600 For the total river width of 144 m as above, 2.70 m long 23 bamboo mats each 90 cm.
4 Wire 500 m coil, coil 2.5 Woven along the upper matting. For 2 units in No. 8 gauge 4 parts, 1152 m are needed for 144 m width.
5 Wire 2040 m coil coil 4 8-gauge wire to twist around the upper matting. No. 14 gauge
6 Oak 1.80 m long piece 97 97 poles at 1.50 m spacing are needed for river pal es top end width 144 m. These poles add strength to the upper
7.5 cm matting.
7 Oak it II II piece 388 Foundation piles at 1.50 m spacing. Enough for four piles rows, of which one quarter are for maintenance.
8 Oak n II H piece 97 Used as bracing for the foundation
9 Oak logs 3.60 m long piece 80 Side poles for affixing the lower screen and the top end upper matting. 7.5 cm
*It will be observed that in some cases, the dimensions given do not agree with those on the drawings. Translator.
'I,
LIST OF MATERIALS (cont'd.)
Total From To Nomen- Quality Number Last Next
No. clature and Size Units Needed Year Year Purpose
10 Larch 3.60 m long piece 80 Side poles to prevent the rocks from being washed logs top end away and to support the upper matting.
7.5 cm
11 Oak 2.70 m long piece 97 Reinforcing poles for the side poles to which the poles top end upper matting is affixed (No. 9).
7.5 cm
12 Larch 1.8 to 3.6 m , piece 97 Poles to prevent up or down motion of the upper mat- poles long top ting (Which could be removed and washed away by
end 6 cm floods).
13 Wire 510 m coil coil 8 Fixing the end points of the foundation piles and No. 8 gauge side poles. Each end uses 1.20 m 3365 ends need
total length of 4038 m.
14 Wire 1, 21 mm coil 2 Up and down movement of upper matting. rope 1, 9 mm
15 Hooks 12 mm, piece 200 5 used on each of the 3.60 m side poles used with round, iron the up and down motion of the upper matting (No. 9).
16 S-shaped 7.5 mm 384 The upper mats (No. 3) each use 4 at 1.50 m spacing. hooks iron
17 Pig iron 0.15 cm piece 388 For pile driving at each point. iron plates
18 Boulders For use in foundations. (To be collected on site.)
19 Willow As above. twigs
LIST OF MATERIALS (cont'd.)
Total From To Nomen- Quality Number Last Next
No. Clature and Size Units Needed Year Year Purpose
20 Nails 6 cm long K 36 For pine lumber cross-bar construction. 3 nails for each cross-bar. CI K contains 270 nails.)
- 15 -
HOLDING ADULT FISH
1. Holding Adult Fish for Egg Collection
Adult fish caught in the river, other than those which will
probably spawn almost immediately, must be held until the gonads ripen.
Usually, the river is large and the spawning places are
distant, so the fish tend to ascend the river early. If the catching
place is in the downstream part of the river, there must be a fairly
long period of holding.
There are various types of holding facilities. Since they
are places in which a large number of adult fish which are still un-
ripe and must be held for a long time„one must endeavour to give them
an environment as close as possible to that in the river.
2. Types of Holding Facilities
(1) Fish Tanks (pens)
These are used for temporary holding at catching places
where the number of adult fish caught is small. The size, type
of construction and materials are chosen to suite the river
conditons.
(2) Double Stop
Holding ponds may be constructed directly in the river
in places where the current velocity is not too high, where there
is little fear of sudden flooding and where there are places up
or downstream where the adult fish naturally congregate, and
where weirs may be installed.
These can be expected to provide a desirable environ-
ment for the fish, but they are difficult to operate, and difficult
to build.
(3) Holding Ponds on Land
Simple dug-out ponds, wooden-fenced ponds and concrete
ponds may be built on land. For long-period holding, they need a
- 16 -
supply of water, and where there is an abundant supply of good
quality water they can be the most suitable places for holding
fish.
(4) Holding Ponds in the River
Holding ponds made by partitioning off part of the
river may be used, but there is some risk that the adult fish
will escape during flooding. Ways must be devised in advance
to prevent this.
3. Important Items in the Establishment of Holding Facilities
(1) Short-Period Holding
(a) Fish tanks may be used for temporary or provisional holding
before transfer to the holding pond, but in their construc-
tion, careful consideration must be given to the shape of
the tank, the materials, the location, the river conditions
and the number of fish to be held per day.
(b) Piles must be sufficiently firm not to be washed away during
flooding.
(c) Covers must always be provided to protect against direct
sunlight.
(d) When the water depth is about one metre, the size of the
fish tank should be such that there will not be more than
50 fish per square metre.
(e) When fish tanks are installed close to a river mouth, the
water current will stagnate at high tide, and oxygen defi-
ciency may occur if the tank contains too many fish. Such
conditions must be avoided.
(2) Long-Term Holding
(a) When unripe adult fish are to be held for a long time, they
must be kept in an installation which is as close as possible
to the environmental conditions of life in the river which
they are ascending.
01
(2).
- 17-
(b) The holding pond should be as close as possible to the catching installation. If the distance of transport is long, the adult fish will be badly affected, and the operat-ing expenses will be large.
(c) They must be contained in holding ponds with an abundant supply of good-quality water. There is no problem if natural river water can flow in, but if it is to be pumped up, a reserve pump with its own power supply must be installed in case of breakdown. rf electric motors are used, a private supply or diesel engine must be installed, with arrangements for prompt switch-over in case of power supply failure, so that the length of a failure of water supply is kept shorter.
(d) The quantity of water supplied is related to the number of adult fish held, and to the number of fish to be transported at one time, and it must he possible to increase or decrease the water input.
(e) The water used must have little suspended matter and suffi-cient dissolved oxygen, and during rainfall little muddy water may flow in.
(f) Rapid changes of water temperature must be avoided by using a sufficient water depth and hy covering the water surface so as to avoid the temperature effect of strong sunshine.
4. Advice on Holding Management
Since there is a close relation between the quanity of dissolved oxygen (D.0.) and the amount of crowding, these must always be carefully considered and, if necessary, the D.O. should be measured.
Since the dissolved oxygen decreases as the temperature rises, the number of fish held should be decreased when tempera- tures are high.
-
(3 )
(4)
(5)
(6)
(7 )
— 18—
Since the amount of the oxygen consumed by the fish
increases when they are agitated, people should, so far as pos-
sible, avoid going close to the holding pond.
A suitable current speed in the holding pond is about
10 centimetres per second. rf the current speed becomes too great, the amount of motion of the fish increases, the amount of
oxygen consumed risës and their physical strength may be largely exhausted.
Because of this, it is necessary during long-term
holding to provide places where the current speed is small, and
the fish can rest.
Adult fish which are being held can easily be influ-
enced by human shadows and by noise. If such conditions occur
frequently, they cause stress, and wounds are often produced by
abrupt movements. Unnecessary human and vehicle approaches must
be avoided as far as possible.
Various fish diseases can easily arise if the water
temperature varies or if dirty water enters, so the condition of
the fish must be carefully monitored. Sick and dying fish must
be removed as soon as possible, and disinfection and medical
treatment must be provided under the guidance of professional
experts.
As to the proportions of male and female fish to be
held, the number needed for fertilization is one male for three
to five females, so in order to utilize the holding pond suffi-
ciently, it is appropriate to have one male to each three females.
- 19 -
Generalized sketch of a "double stop" holding pond
UP-STREAM WEIR
The desirable place will have a large surface area, and one part of the river will be deep and the water will be slow-moving.
DOWN-STREAM WEIR
" DOUBLE - STOP " HOLDING POND
Example of a holding pond on land -
(A fixed wooden fence holding pond)
Both inlet and outlet of water are under control. The water input and the condition of the fish being held must be carefully considered.
FIXED WOODEN FENCE HOLDING POND
(1)
(2)
— 20 —
THE COLLECTION OF EGGS AND SPERM
1. The Selection of the Adult Fish
(1) Since good quality eggs cannot be obtained from unripe
or overripe females, the adult fish to be held must be repeatedly
examined, and those which are ripening must be chosen, so that
the appropriate moment is not missed.
(2) The choosing should ideally be done in the water. Since the
examination will be made many times before the spawning period,
and since good or bad handling of the fish will affect the
development and hatching of the eggs, the fish must always be
handled carefully with both hands.
(3) The following criteria are used to decide on the ripeness of the
female fish:
(a) For breeding, the colour of the fish body darkens.
(h) Lifting the tail shows that the abdomen, particularly the
part under the pectoral fins, is swollen, and the abdominal
wall by the vent has sunk, producing wrinkles.
(c) The abdomen is much softer than during the unripe period.
2. Killing the Ripe Adult Fish
The ripe adult fish which are to be used for eggs or
sperm should be killed by clubbing immediately before use. Acci-
dental heavy pressure on the abdomen during killing will result
in dead eggs. One person should therefore hold the tail and
chest and hold the head forwards, and another person should
strike hard between the eyes and the snout.
When eggs are to be collected from a large number of
fish, the operation of egg collection may be postponed for con-
venience. (If a long time elapses after the killing, there is a
risk that the amount of sperm obtained will be diminished.)
(1)
(2)
(3)
-21 -
3. Transfer of the Fish Used for Egg Collection
(1) In order to transport the killed adult fish to the egg
collection room, a container is used in which they can be placed
head-downwards.
When there is a small number, they may be transported
by hand, but they must not be transported in a heap. In places
where a large quantity of eggs are to be collected in a short
time, the efficiency can be increased by a belt conveyor, a pipe,
or tubs.
Since the eggs and the sperm are badly affected by rapid
changes of the body temperature of the fish, the adult fish,
after killing, must be transported to the egg collection room as
rapidly as possible, without being exposed for a long time to
direct sunlight or to cold atmospheric temperatures.
4. Egg Collection
Normally, one person will hold the head, and the other
person will hold the caudal peduncle. A gutting knife (there
are various shapes) is inserted shallowly into the vent, and a
single cut is made to the vicinity of the pectoral fin. Eggs
remaining in the abdominal cavity are gently extracted by hand.
This must 5e done carefully, since the eggs will be
injured if the gutting knife goes too deep and enters the ovary
while cutting. If the cut is too deep in the neck, a large
amount of blood will come out, so care must be used there. If
water, body fluids and blood are mixed with the eggs as they are
collected, the relative amount of semen will be reduced, so this
must be given sufficient attention.
A round, shallow egg collecting dish is often used for
holding the eggs, but there is no need for a particular type of
dish; any dish made of plastic or of any other material is all
right, if convenient.
(2)
(1)
(2)
(3)
(1)
(2)
- 22 -
5. Sperm Collection
Two persons are usually employed to squeeze out the
semen. The assistantholds the head; the semen collector grasps
the caudal peduncle with one hand and first removes the dirt
from the abdomen. He then squeezes downward the part just above
the vent, and the dirt expelled is thrown away outside the egg
collecting dish.
Since the whole of the seminal glands do not ripen at
the same time, the portion nearest to the tail is gently squeezed
and the pure semen is poured over the eggs in the egg collecting
dish. Good quality semen has a thick, pure white colour. Any-
thing tinged with green, yellow or black, or mixed with blood or
visceral slime must not be used.
If there are few adult male fish, semen can be collected
from them while alive, without killing, and in this case, they
can be held and used several times. Since there is water in the
abdominal cavity when they are re-used, care must be taken that
this does not penetrate among the eggs.
6. Fertilization
Ova from several fish are placed in the egg collecting
dish, and the semen from at least two males is added. This is
to avoid the possibility that if only one male isused, the sperms
will be completely inactive, and there will be no fertilization.
The ova and the semen must be suitably agitated. This
is to be done by hand in order to avoid shock to the ova, or the
feathers of a water bird may be used. If the eggs are damaged,
their contents flow out into the water used for fertilization,
and the rate of fertilization is reduced, so care is essential.
(3) The mixture of ova and sperm is not sufficient for
fertilization, because the sperm will not become active until
they are in fresh water. After the ova and sperm have been
thoroughly mixed, the fertilization water must therefore be added.
14.
- 23 -
A shower is advantageous, but if the water is poured on, care
must be taken to avoid shock, and gentle agitation must continue.
If the water used for fertilization contains salt, the
fertilization ratio will be reduced, so good quality pure water
at 5°C is to be used. (The time required for the completion of
fertilization is two to three seconds.)
7. Water Absorption and Washing
(1) The fertilized eggs absorb water and begin to swell
after several minutes. After 10 to 20 minutes, they will begin to be stuck together by surplus semen, so 5 to 10 minutes after fertilization, they are moved to a washing tub, in which water
absorption as well as washing is completed.
(2) If the number of eggs fertilized at one time is small,
it is permissible to wash them and to allow them to absorb water
in the egg collection dish. In this case, it is necessary to
take care to remove impurities.
(3) When water absorption is complete, the eggs are swollen
and have become elastic. At about 70C, the period needed is about 60 minutes, and at lower temperatures, a longer time is required. Care must be taken over this, since incomplete water
absorption is a cause of bad eggs.
(4) The desirable type of a washing tub is a water barrel
with a metal mesh stretched across the bottom, so that the water
enters from below and flows out over the top. The amount of
water should be such that the eggs are not agitated and made to
float upwards.
(4)
(1)
(2)
(3)
(4)
(5)
- 24 -
TRANSPORT OF THE EGGS
1. Transport Directly after Fertilization
Eggs in the egg collection shed which have finished
absorbing water are fairly resistant to pressure applied from
the outside, but, since they have Little resistance to impact,
they must be handled cautiously.
Transport boxes should be of a size which is easily
managed. Normally, a wooden egg transport box is used which
will contain 50,000 eggs (490 mm x 265 mm x 210 mm), but when
a large quantity of eggs is to be transported, a transport box
900 mm x 330 mm x 300 mm which will contain 200,000 eggs is
used.
The transport box is gently filled with eggs which have
previously been well washed. A dampened bleached cloth is laid
over the eggs, then an intermediate cover is added, and on top
is placed a sponge mat or blanket containing water and secured
by rope. In this way, the eggs are under sufficient pressure
that they will not move, but this must be done carefully, since
too great a pressure may be a factor in hindering the proper
development of the eggs.
The sperm nucleus and the ovum nucleus will have finished
uniting when about two hours have elapsed since fertilization,
and the blastodisc will have started to divide. At this time,
the egg is in a condition in which it is sensitive to impact and
agitation, so transport to the rearing shed must by then be com-
pleted (within eight hours).
The interval from fertilization to the first division of
the blastodisc depends on the environmental temperature of the
egg, and the following general intervals are given for reference:
•■■
15°C
13° to 14°C
9° to 12°C 7° to 8°C 3° to 4°C
about 6 hours
about 8 hours
9 to 11 hours
10 to 12 hours
24 hours
-25 -
2. Transport in the Eyed Stage
(1) In the period reaching from the eyed stage to about five
days before hatching (280° to 440°C), the fertilized eggs have
relatively high resistance to external pressure and impact, so
that long-distance transportation may occur during this period.
(2) When egg transport boxes are to be loaded onto trucks,
anti-shock materials must be spread out first, and the egg trans-
fer boxes loaded onto them so as to prevent vibration. They must
be secured firmly.
During transport, the temperature of the eggs must be
maintained at 3° to 8°C. Blankets and heating appliances must
he used during cold weather, and ice during hot weather, to
maintain the proper temperature.
(4) When large quantities are to be transported, it is
advantageous to use vehicles whose internal temperature can be
maintained at a fixed level.
MEMO
( 3 )
- 26 -
EGG STORAGE
1. When the egg transport boxes arrive at the hatchery and are
unpacked, the temperature must always be measured.
2. The eggs must not be immediately placed in the water if the
difference between the temperatures of the eggs and of the water is
4oC or more. They must be kept in the transport boxes, and water is
to be poured gently over the boxes and onto the eggs. When the egg
temperature is as near as possible to that of the incubation water,
they are removed from the boxes and put into temporary holding tanks.
3. The temporary holding tanks are needed to hold the eggs
until hatching (hatching trays or baskets),and the Atkins-type of dual
purpose tanks is usually used. The quantity of eggs to be held in one
tank is then to be limited to at most 150,000.
4. Eggs adhering to the inner wall of the transport box are
not to be forcibly removed. The box is to be washed with water so
that the eggs can peel away naturally.
5. When eggs are moved into temporary tanks, they are spread out in the
incoming water. Agitation and impact of the eggs caused by the water
flow are causes of egg death. This is avoided by partitioning the
incoming-water part with metal mesh or by other means, to diffuse the
flow.
6. Eggs should be held for as short a time as possible. It is
particularly necessary that transport to the storage tank should be
completed within eight hours, directly after fertilization.
7. The process of placing eggs in the tank must always take
place in water. In particular, great care must be taken to subject
eggs which have just been fertilized to as little impact as possible.
-27 -
8. When Atkins hatching tanks are used, the normal level is
100,000 to 120,000 eggs per tank. With hatching trays, it is 2,500.
When eggs are kept in hatching trays, the tray is held horizontally
in the water with the left hand, eggs are scooped up by means of an
egg scoop in the right hand and moved over the tray and gently moved
up and down, back and forth, to distribute them uniformly in rows.
9. In a rearing and stocking facility which uses basket-type
incubation, there will normally be 5,000 eggs per basket. However,
10,000 may be held per basket from directly after fertilization to
the eyed stage.
10. Whether the Atkins or the basket-type is used, great care
is required to ensure that the water normally flows uniformly through
all parts of the incubator.
When eggs are transported, they must always be accompanied
by lists of the number of eggs, the place of collection, the dates of
collection and of arrival at the eyed stage, and the anticipated date
of hatching, and these list must always be checked. When eggs that
have been locally collected have been fertilized, the egg diameters
and egg weights are measured in order to compute the exact number of
eggs.
11.
- 28 -
CALCULATION OF THE NUMBER OF EGGS
The number of eggs may be calcu1ated from the wéight, the area
or the volume, but the weight method is simple and is now Most frequently
used. There are thé two following methOds:'
Before the eggs are removed from the transport boxes to the
temporary holders, the total weight is measured, the weight of eggs
is determined by subtracting the weight of the box, and the number of
eggs is determined by using a standard weight for an egg.
(Example of calculation.)
Suppose that a definite number of eggs, such as 100, has
been extracted and the total weight obtained, with the result that
one egg weighs 0.35 grams. Next, if the weight of the transport box
containing the eggs is 32.18 kg, and the weight of the box is 2.15 kg,
the number of eggs is:
Total weight of transfer box - weight of box alone
Weight of one egg (grams)
32.180 - 2.150 - 85,800 eggs.
0.35
2. The number of eggs in a weight which is a suitable fraction
(a subsample) of the total egg weight is counted, and the number of
eggs is determined by using proportionality.
(Example of calculation.)
1.
■■•
(1) Suppose the weight of eggs is 17.5 kg:
(a) Suppose the number of eggs in one-hundreth part of this
weight, or 175 grams, is found. It is then to be multiplied
- 29 -
by 100. Thus, if 175 grams corresponds to 500 eggs, then
100 times this is 50,000 eggs.
(2) If the total weight of eggs is 35 kg:
( a) Then 175 eggs is one 200th-part, and the number counted is
to be multiplied by 200 -
175 g = 500 eggs
500 eggs x 200 = 100,000 eggs.
(2)
(3)
- 30 -
EGG MANAGEMENT
The general principles for the management of the eggs are that
the water conditions must be kept suitable, and that every possible effort
should be made to prevent physical or chemical changes. The points which
must receive sufficient attention have been summarized under the following
headings:
1. The Influence of Light on Eggs
(1) The ultraviolet part of the sunlight is harmful and,
since eggs which are exposed to direct sunlight all die within
a few days, it is absolutely essential to take care of this
point.
The windows of the Incubation room should be of frosted
glass or have curtains to prevent exposure to direct sunlight.
Indirect light rays in the incubation room are not
particularly harmful, but since fluorescent bulbs produce a lot
• of ultraviolet light, it is possible that when they are used
there will be damage if the floodlights are close to the eggs,
so they should be kept as far apart (away) as possible.
2. Conditions in the Incubation Water
An increase or decrease of the temperature of the
incubation water will have an enormous influence on the speed
of development of the eggs. It is said that an increase of 1 0C
in the water temperature will cause the time of hatching to
arrive about five days early. It is therefore important that
changes of incubation water temperature should be small, and,•
for salmon incubation in particular, spring water or river-bed
water is desirable.
(1)
The incubation water should have an oxygen content of
50 percent to 9_0 percent saturation, it should be colourless, and
(2)
(3)
-31 -
it should not contain suspensoids or mud. The hydrogen ion concentration (pH) should he close to neutral (p 117).
With karafutomasu (Oncorhynchus gorbuscha, pink salmon) and sakuramasu (Oncorhynchus masou, cherry salmon), it is desir-able to use river water for incubation. This is because in
natural conditions, the eggs of both salmon and trout develop in
water which has percolated down from the river. In order to con-
form with the normal river conditions at this season, which is at
or after the latter part of March, incubation water with the
lowered winter temperature and the abundant dissolved oxygen of
river water will be the most suitable.
During the incubation period, it is necessary that the amount of water should neither increase or decrease. Rapid
changes of the amount of water may lead to asphyxiation, due to
lack of oxygen or to impact with the water current, and both can be causes of death. Too much or too little water can have good or bad effects on the results of incubation.
Sudden changes of water temperature during the incuba-
tion period may be the reason for the development of deformed
fish, so care must be used when fertilized eggs are relocated.
3. The Quantity of Water Inflow
(1) The quantity of water depends on the incubator or tank, but the following are standard values:
(4)
(a) Atkins-type incubation tanks (b). Atkins-type, large
(c) Box-type incubator , (d) 3-D incubator (eggs)
(e) 3-D incubator (fry)
1 row, 20 litres per minute
1 row, 30 litres per minute
1 row, 50 litres per minute 1 rack, 9 litres per minute 1 rack, 12 litres per minute
The flow for basket-type incubators is the same as for
3-D incubators, (d) and (e).
WATER INTAKE INSERT PARTITIONING SHEETS OF ALUMINUM PLATE ,ETC.
WATER LEVEL
- 32 -
(2)
(3)
The water level in the Atkins incubator should submerge
the upper metal mesh. The metal mesh of the incubating tray is
to be parallel to the water flow direction, and the water inlet
of the incubator frames should always be in the direction in which
the incubating water is received into the incubation tank.
In the basket-type, the eggs in the uppermost level of
the basket must be submerged. Also, when baskets are used as
partitions in the rearing pond, it is necessary to ensure, with
care, that the water flows through all parts of the basket.
When baskets are used In Atkins-type incubating tanks
(see diagram), two partitioning boards are to be inserted between
each of the baskets, so that the water always passes through the
baskets from the bottom to the top. •
BASKET TYPE INCUBATOR
INCUBATING TANK
Notes Degree-total
from fertilization to hatching
Species
About 5600C to 580°C The eggs are weak and should not be touched until half the degree-total has been exceeded.
Karafutomasu Oncorhynchus
gorbuscha (Pink Salmon)
Masumosuke Oncorhynchus
tschawytscha (Chinook Salmon)
About 578°C ti
- 33 -
4. The Degree-Total and the Number of Days to Hatching
(1) The number of days which fish such as salmon and trout
require for hatching depends on the temperature of the incubation water, but the total number of degrees, which is called the
"degree total" is almost constant. Thus, by using the degree-
total and dividing it by the average temperature of the incubation water, it is possible to estimate the number of days required for
hatching.
(2) The degree-total from fertilization to hatching for each of the fish species is shown in the Table:
Sake They are most sensitive Oncorhynchus keta About 480°C to impact when the (Chum salmon) degree-total is 105o to
If daily average is 8°C 1350C. 60 days
Weakness extends from If daily average is 4°C the eyed stage to 270°C,
120 days and they should not be touched.
Sakuramasu Oncorhynchus masou
(Cherry salmon)
About 4400C to 450°C
I I Himemasu Oncorhynchus
nerka v. adonis (Kokanee salmon)
About 6600C to 7600C
Beni sake Oncorhynchus
nerka v. nerka (Sockeye salmon)
About 660°C to 760°C
(1)
(2)
(3)
(4)
(5)
(6)
- 34 -
5. The Disinfection of Eggs and the Removal of Dead Eggs
In order that thgy should not be exposed to
impact or vibration, the eggs stored in the incubator must not,
as a general principle, ever be touched before they reach the
eyed stage.. Thus, before the eyed stage, the eggs will not be
inspected, and dead eggs will not be removed.
If dead eggs are present, water-borne fungi will
grow, and if this condition is neglected, the fungi will spread
to other eggs which will be killed. This can be reliably pre-
vented by disinfection with malachite green.
Disinfection may use the immersion or the drip
method, but the most simple method uses a controlled-flow siphon
which drips a malachite green stock solution into the incubator
water.
The concentration of malachite green to be used
is one part in 200,000 to 400,000.
The standard period for disinfection is one hour,
each five to seven days, but the concentration of the disinfec-
tant solution and the interval between applications can be
increased or decreased in response to the state of development
of the fungi.
If the development of chorion softening is feared,
potassium permanganate may be used jointly with malachite green
as disinfectant. In disinfecting, the stock solution is dripped
into the incubator water for 30 minutes to provide a concentra-
tion of one part in 40,000 to 80,000.
This disinfection should be used three times in
the period before hatching. The concentration used is one part
in 80,000 after loading into the incubator, one part in 40,000
before the eyed stage, and one part in 40,000 after the eyed
stage.
"04
4L
(7)
- 35 -
In greater concentrations, both malachite green and
potassium permanganate are harmful to young fish, and it is
necessary that during disinfection, the incubator water should
not enter the young-fish pond and come directly into contact
with the young fish.
If it should enter, it can easily be diluted. In
addition, malachite green can be neutralized by adding sodium
sulphite, and potassium permenganate can be reduced by adding
sodium thiosulphate.
The neutralization of malachite green solution
Concentration of Quantity of sodium sulphite disinfectant in to be added to each litre of the outflow, the outflow
1 in 200,000 1.2 cc of 0.8% solution
1 in 300,000 0.8 cc of 0.8% solution
1 in 400,000 0.6 cc of 0.8% solution
1 in 600,000 0.4 cc of 0.8% solution
1 in 800,000 0.3 cc of 0.8% solution
The reduction of potassium permanganate solution
Concentration of Quantity of potassium permanganate
disinfectant in to be added to each litre of the the outflow. outflow.
1 in 40,000 0.33 ml of 20% solution
1 in 32,000 0.165 ml of 20% solution
1 in 100,000 0.132 ml of 20% solution
1 in 1,000,000 0.0132 ml of 20% solution
- 36 -
REFERENCE MATERIAL (No. 1)
The Controlled-Flow Siphon Method of Egg Disinfection
It is reported that when the controlled-flow siphon method of
egg disinfection is used, good results are obtained from the use of a
solution of one part in 200,000 of malachite green for one hour every
half week.
The Preparation of the Stock Solution in the Siphon Bottle ,
If the amount of incubation water which enters the incubator
tank each minute is taken as 18 litres, and the concentration of malachite
green desired for disinfection is to be one part in 200,000, the method of
preparation of the stock solution can be worked out as follows:
1 : 200,000 X : 18,000 cc
X = 13 ' 000 x 1 = 0..09 grams per minute '
200,000
Thus, 0.09 grams of malachite green per minute are required.
In order to decide on the concentration of the stock solution in the
siphon bottle, the rate of flow of the stock solution from the siphon
bottle must be determined. If this rate of flow is 30 cc per minute,
1,800 cc must drip out for one hour of disinfection.
The concentration of malachite green in one cubic centimetre
of water is 1/30 of 0.09 grams, or 0.003 grams, and 100 cc will contain
0.3 g, so that the strength of the solution is 0.3 percent.
Since1,800cc must drip out if the disinfection is to last for
one hour, it is necessary to put at least 2,000 cc of stock solution into
the five-litre siphon bottle. The stock solution is to be prepared by
dissolving 3 g in 1,000 cc (1 litre) or 6 g in 2,000 cc (2 litres).
The concentration of the stock solution is, in fact, limited
to one part of malachite green in 150 parts of water, for if stronger
- 37 -
solutions are made, they may become over-saturated, and there is a risk that malachite green crystals will be precipitated. It is necessary to take note of this.
An example of a controlled-flow siphon.
Outer diameter 16.6 cm, height 35 cm Glass Tubing outer diameter 9 mm, rubber tubing 11 mm Glass tubing protions are C, E, H, J Rubber tubing portions are F, I, K.
(1 )
(2)
(3)
(4)
(5)
- 38 -
MANAGEMENT DURING THE HATCHING PERIOD
As the hatching period approaches, froth appears and
gathers at the outlet of the incubation tank or in the upper portion
of the incubation tray, and when the hatching is in full swing, the
surface of the incubation tank may be covered by froth. This is pro-
duced by an enzyme which is secreted inside the eggs to liquify the
egg membranes, and when it is seen to appear, the following procedures
must be used:
As the hatching period approaches in the Atkins-type
incubator, hooks (made of wire) are passed through holes in the
corners of the incubation frame which is hung from the edges of the
incubation tank at about 10 cm from the bottom. This allows the
hatchlings to slip through the mesh of the incubation tray or to
swim out past the corners and to gather together on the bottom.
However, since the newly-hatched fry have large egg yolks,
there is a risk of suffocation of those at the bottom of a large
pile. The newly-hatched fish must therefore be sucked out of the
incubating tank by means of a siphon and transferred to the fry pond.
At the same time, the number of eggs still being incubated in the
tank is gradually diminishing, and they should be brought together
so as to reduce the number of tanks.
Great care must be taken to cause as little physical
impact as possible when the fry are moved from the incubation tank
to the pond. In particular, when they are scattered into the fry
pond, it is important that they should come gently into contact
with the bottom.
It is not necessary to remove the hatchlings to the fry
pond from the vertical or the basket types, because there is room
for them until they float upwards when the umbilical cords have
been absorbed. However, a large number of cast-off eggshells accumu-
late on the metal mesh or on the meshes of the baskets, and they must
without fail be removed several times daily.
f
■
(1)
(2)
- 39 -
As the hatching period approaches, the activity of the incubation enzyme can be strengthened by decreasing the water
quantity by one-third, and since the eggshells are then completely liquified, the process of removing the eggshells also becomes extremely efficient.
MANAGEMENT OF THE FRY
This must he done with great care, since the quality of
management of the fry can result in great variations in the amount of growth. •
1. Environmental Conditions in the Fry Pond
"Fry pond" is a general term for the surfacing pond and the rearing pond. These have the following individual func-tions, but they are generally combined:
(a) The Surfacing Pond This is the pool for holding the newly-hatched fry during the period between hatching and coming to the surface.
This period depends on the water temperature, but at 8°C
it is 20 to 30 days.
(b) The Rearing Pond The fry are released into this pond after they have surfaced, and are given food for growth. The state of growth is to be checked monthly.
The quality of the environmental conditions in the fry
pond is strongly connected to the growth after hatching, and par-
ticular attention must be given to the following points:
(a) The pond is to be kep clean.
(h) The quantities of inlet and outlet water must be easily
controlled.
(p) A definite water quality and rate of flow must be maintained.
(1)
(2)
(3)
- 40 -
(d) The water flowing through the pond should not anywhere
stagnate or drift sideways.
(e) The entrance of harmful birds, animals or fish must be
prevented.
(f) The pond must he completely covered with awnings to that
there is no direct sunlight.
Since disease producing fungi, harmful animals and
harmful fish can easily breed or enter, the pond should be
cleaned out and disinfected with lime before use. This is par-
ticularly necessary in ponds into which mud or organic matter
can flow.
In order to disinfect with lime, the pond is first
thoroughly cleaned whîle the water flows through. The water is
then cut off, and quicklime is spread at the rate of 600 grams
for 3.3 m 2 . It is then refilled with water and left for one to
two days. Finally, the water is allowed to flow through so as
to flush the lime solution completely away.
If quicklime is not available, about twice as much
slaked lime may be used.
2. Management of the Hatchlings
When the Atkins-type incubator is used, the newly
hatched fry must be promptly transferred to the surfacing pool.
If the condition of the water used is good, eggs which are about
to hatch may also be transferred.
Normally, the newly-hatched fry are gradually dispersed
from the downstream part of the pond to the upstream part. If
fry in different stages of development are put in, there will be
trouble with cannibalism, so if the fry are in very different
stages, they must necessarily be separated by partitions.
The population density in the pond depends on the rate
of water flow, the water quality and the construction of the pond
but, in general, 3.3 m 2 (one Japanese utsubon) can take 20,000 to
40,000 fish.
(3)
(4)
(5)
(6).
(7)
(8)
(9)
- 41 -
Up to the stage when the fry come to the surface, the
amount of water in the fry pond must be controlled so that the
fry in the pond are not pushed together by the current. A normal
value for a pond with 100 to 200 cubic metres will be 300 to 500
litres per minute, with a water depth of 15 to 20 centimetres.
Before the yolk sac is absorbed, the fry will swarm
together and can easily suffocate. This is particularly likely
in the water inlet part of the pond, so trouble must be taken
about an even distribution over the whole area of the pond and
about the water inlet.
When fry and eggs which are about to hatch are placed
in the pond, awnings must be spread over them to exclude direct
sunlight. Fry which have not yet absorbed the yolk sac have very
little resistance to direct sunlight and are greatly affected by
four to five hours of exposure. This remains dangerous for about
30 days after hatching. More than 50 days after hatching, there
is practically no such effect.
Solid incubators or basket incubators differ from the
Atkins-type in that after hatching, the fry are not removed to
the fry pond until the absorption of the sac is finished, and the
fry come to the surface. They are then transferred to the rear-
ing tank or rearing pond and are fed. In this case, the incubator
mesh may be blocked by the corpses of a large number of dead fish.
There is some risk that this may cause an oxygen deficiency and
result in a large number of deaths, so the mesh must be periodi-
cally inspected, and any corpses blocking it must be removed.
After the fry have hatched, the quantity of oxygen
consumed increases, so usually one must take note of the dis-
solved oxygen and the pH and calculate the appropriate water
inflow.
The condition of the fry in the rearing tank or rearing
pond must be continually checked, and appropriate measures must
be taken if anything unusual occurs. Sick or dead fish must be
removed.
(1)
(2)
(3)
(4)
(5)
- 42 -
3. Feeding and Rearing of Fry
In order to increase their health and to improve the proportion which survive, and also to promote their successful return after going down to the sea, salmon and trout fry which have reached the stage of coming to the surface are normally fed before being released.
Hatchlings which have been transferred to the fry pond come to the surface and begin to swim when 80 percent to 90 per-cent of the yolk sac haS been absorbed. At this time, the digestive organs have developed sufficiently for them to be able to feed, so the provision of feed should start. The awnings are also to be removed.
In order to accustom the fish to the feed, it is given as a very fine powder for about the first week. The amount pro-vided at one time should be small, the rule being to feed frequently% An approximate norm is 10 to 12 times per day.
When feeding is established, a gradual change is made from powder to "crumble." If commercially marketed food is used, these species require "mash," "crumble No. 1" and "crumble No. 2."
The diet requirements of the fry depend on the water temperature, the weather, the environment in the rearing pond, the quality of the feed, the health of the fry and the degree of absorbtion of the yolk. The feed is to be given several times per day in response to the requirements of the fry. A normal condition is three to six times per day. This must be tightly controlled, since an excess of food contributes to a deteriora-tion of environmental conditions in the pond.
The objective of feeding and rearing is to increase the body weight of the fish, and during the period this should, as a standard be doubled in a month. The usual method of feeding is to sprinkle the food in the air onto the water surface. >t,
(6)
(7)
- 43 -
The water in the pond in which the fry are reared and
fed should be as deep as possible, and must at least be more
than 30 cm deep. The ideal is that the oxygen should be 70 per-cent of saturation in the inlet water. The amount of water
should, as a standard, be three times as much as in the incubator.
The quantity of food to be given per day is propor-
tional to the weight of the fish, as shown in the following
table:
Table of normal food ratio.
Water Temperature °C 3 4 5 6 7 8 9 10 • 11 12
Food ratio (%) 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.4 3.6 3.8
(The food ratio is the amount of dry food per day as a percentage of the fish weight.)
REFERENCE MATERIAL NO. 2
The Proper Method of Measuring Water Temperature Scoop up the water in a bbcket, throw it out, scoop it up once
again, and place the thermometer in it. Lmmerse it in the water as far
as the portion to which the mercury line has risen, shield it from direct
sunlight, wait until the mercury line is completely steady and take the
reading. Endeavor to make the line of vision perpendicular to the
thermometer.
If there is a break in the mercury line of the thermometer,
place it in a mixture of ice and salt, and after the mercury has completely
withdrawn into the bulb, take it out quickly and tap it lightly on a sheet
of rubber or other yielding material till the air bubble escapes. Further,
if part of the mercury line does not go down, shake it gently, and it will
usually come down.
(From Yatsuka SAIJO, Kosho chosa ho. (Methods in limnology).)
(1)
(2)
(3)
-44-
ATER SURFACE
The Release of the Fry
In natural conditions, the fry (pink and chum salmon)
would go down to the sea after coming to the surface, using bottom-
dwelling animals as food. The migration of the fry from fresh water
to sea water requires a great physiological change, and the response
to sea water is easiest about 90 days after surfacing. When this
period is past, up to about 150 days after surfacing, the transition
results in physiological damage, and frequently in death. The period
of easiest adjustment to sea water is different for other species of
salmon and for trout.
After surfacing, the fry would be in the river water, with
a temperature of 3° C to 4°C. As they go down-river, there will be
the snow-melt flooding rush at 5° to 6°C, and at 12° to 13°C there
will be the transition from the brackish water of the river mouth to
the offshore water. The fry will move around, actively seeking for
food, and will grow rapidly.
In the offshore region, where river water and sea water
are mixed, there is an abundance of zooplankton (containing the
larvae of fish and marine animals) resulting from the nutrient salts.
These are the food for the salmon and trout, and it is no exaggera-
tion to say that on them depend the active motion and the bodily
strength of the fry (the juvenile salmonids) which determine the
proportion which returns after going out into the oCean.
•
•1!■
•
-45 -
(4) The period during which salmon and trout fry and smolts
remain in the offshore zone may vary somewhat according to the
species, but if the temperature éxceeds 15°C. they will leave because
they cannot endure higher temperatures. One must therefore be care-
ful to time the release of the fry or smolts so that they will have
an offshore feeding period of about one month.
In order that the appropriate time for release of fry may
not be missed, it is necessary to observe the offshore water temper-
ature, with particular reference to the influence of the Tsushima
warm current and the regions of rapid increase of temperature in the
Sea of Japan and on the Pacific coast of southern Hokkaido. It is
sometimes unavoidable that the feeding period for the fry must be
shortened, or they may even be released without feeding.
It is believed that the percentage of fish which return
to rivers which have installations for the release of fry will be
increased if the fry are held in these installations and fed for at
least one week so that they become sufficiently familiar with the
river water. There must therefore be no errors in the supply of
eggs and fry, in the temperature of the water used for their incuba-
tion and rearing, or in the time at which they are moved.
In order to reduce the loss of the fry while going down-
river, it is necessary to look out for destructive enemies. If they
may have to pass localities where they may wander into irrigation
ditches or where the water is extremely polluted, they may be moved
past these sections by land and released downstream. In order to
reduce such influences and make them as small as possible (minimize
their effect), it may be necessary to release the fry in river
tributaries.
THE CONDITION OF THE INCUBATING AND REARING WATER Since the water in which incubation and propagation occur is an
extremely important environmental factor for the fish, it is necessary to
ensure a good quality of water.
(5)
(6)
(7)
•
- 46 -
The fitness of the water can be analyzed by various chemical
techniques, and before operations are commenced, analyses should be made
and advice obtained from professional agencies about the quality of the
water it is intended to use.
There are a number of water conditions which must be present.
These chemical qualities can be measured locallywith simple apparatus and elementary technology, and the information needed for deciding on the
suitability of the water will now be discussed.
1. The Hydrogen Ion Concentration (pH) The pH shows the acidity or alkalinity of the water.
pH = 7 is neutral, alkalinity goes from 7 up to 14, and acidity goes from 7 down to 1. In pure river water, the pa is close to 7, but in
water from bore-holes, the pH is low and acid, directly after being pumped up. Moreover, since some waters become practically neutral
after exposure to the air, they must be spread out for aeration if
it is decided to use underground water. In general, water with pH
from 6.5 to 7.5 is considered satisfactory for use.
The methods of measurement of pH include the use of a pH
meter with a glass electrode, the addition of indicator chemicals for
pH measurement to the water sample and comparison of the change of
colour with standard tubes, and the insertion into the water of pH
test paper whose colour will indicate the pH. Despite a rather
inferior accuracy, pH test paper is convenient and cheap for local
testing.
2. Dissolved Oxygen (D.0.)
Since the oxygen consumption of cold-water salmon and trout
is large, it is necessary that dissolved oxygen should be abundantly
present in the water used, and the abundance or scarcity of dissolved
oxygen is an important element in determining satisfactory rearing.
The saturated amount of dissolved oxygen is 11.5 ppm, at a 1 water temperature of 80C; 11 ppm at 10°C and 8.8 ppm at 20°C.
-47 -
An amount sufficiently close to the saturation value is present in clean river water, but if underground water is used, there may be little oxygen and a lot of nitrogen gas. This may be a cause of gas disease if it is used for rearing, so it is necessary to use sufficient air during aeration. When used for rearing, river or lake or marsh water with more than 6 ppm is desirable, and for salmon and trout it should be more than 7 ppm.
A D.O. meter employing the Winkler method is used for measurement, but this requires skillful operation and is complicated by the preparation of test chemicals, so it has recently become advantageous to use commercially marketed oxygen determination sets.
3. Chemical Oxygen Demand (C.O.D.) C.O.D. is usually used as an indicator of the quantity of
organic matter in the water, and is one way of knowing whether the water is clean or dirty. The C.O.D. should not rise above a low value and, for rearing water, it is desirable that it should not exceed 3 ppm.
4. Ammonial Nitrogen (NR2 -N)
Ammonia is toxic to fish and aquatic animals. It is practically absent from normal, pure river water or spring water but, water from bore-holes may, depending on the type of ground, contain ammonia.
In general, it is desirable that the ammonial nitrogen
content of water used for rearing should he less than 0.3 ppm.
5. Iron (Fe) Iron is also present only in very minute quantities in
pure river or spring water, but rivers which flow over peat bog, and
water from bore holes may contain a lot of iron.
Iron is an element which is necessary to animals, but rear-ing water which contains too much iron is undesirable, and the maximum iron content should be less than 0.3 ppm.
- 48 -
6. Transparency, Suspended Solids (S.S.)
Transparency and S.S. are used as values for the turbidity
of the water. In pure river water and spring water, the transparency
is at least 30 cm, and the S.S. is less than a few ppm.
To be used for rearing, water which is clean enough so that
no turbidity is visible to the naked eye is of course satisfactory,
but it is desirable that the transparency should at least be 30 cm,
and the S.S. less than 25 ppm.
7. The Silica (S10 2 ) to Calcium (Ca) Ratio
For trout nutrition, the ratio of silica to calcium
(S10 2/Ca) should be less than 4, but, in general, if there is less
silica and more calcium, the growth of the fish is improved.
The individual values given in each of the above sections are
not conditions which must necessarily be met, but the best quality water
should be used, and it is also necessary to take care to avoid any risk
of the inflow of water discharged from nearby mines or of water contain-
ing agricultural chemicals discharged from the farms.
REFERENCE MATERIAL NO. 3
Salmon and Trout which Ascend Rivers in Hokkaido
Sake
Chum Salmon, Oncorhynchus keta (WALBAUM).
Distributed in Japan, Korea, the maritime provinces of Siberia
(Primorskii kray), the Kurile rslands, Kamchatka, Alaska and the western
coasts of America.
The body length is 55 to 100 cm, the body weight 3.5 to 5.0 kg.
At the spawning period, the adult fish exhibit cloudy spots as breeding
colours. The forward tip of the mouth in the males protrudes and is
curved into a hook. ti
They arrive offshore from early summer to late autumn, and the
run up the Hokkaido rivers occurs from September until January of the
- 49 -
next year. They are familiarly known as "akiaji" (literally, "autumn
mackerel").
The body is mature at three to five years, most frequently at
four years, and spawning takes place relatively close to the mouths of
the riVers. The number of eggs laid in one spawning is 2,000 to 3,000. They hatch in about 60 daSrs, and go down to the sea in April to May of
the following year.
Karafutomasu
Pink Salmon (Oncorhynchus gorbuscha) (UALBAUM)
Distributed throughout the northern Pacific area, the Okhotsk Sea, the Bering Straits and the Sea of Japan.
During the spawning season, the snout of the male protrudes, and the back is greatly humped up in front of the dorsal fin. They are
then commonly called "sepparimasu" (literally, "humpback salmon").
The body is small, averaging 1.4 kg, but this changes greatly
from year to year, and it is said to be characteristic that they are
large in years when there are few fish, and small in years of big catches.
They ascend the rivers in June to October, and have a two-year
cycle of activity. Spawning occurs in autumn, hatching and egg-yolk
absorption occurs in the following spring, and they descend to the sea
immediately. They are mature 16 to 18 months after entering the sea, and
return to the river of origin. They go upstream without relation to the
size of the river.
Masumosuke
Chinook Salmon (Oncorhynchus tschawytscha) (WALBAUM)
This is the largest of the salmon. The body length is 70 to
200 cm, the body weight may reach 5.5 kg to 18.0 kg.
They are distributed in the Sea of Japan, north of Niigata; Kamchatka, the Okhotsk Sea and to the north of southern California.
Spawning occurs in relatively small tributaries, but the upriver run is characteristically confined to large rivers. The run may occur in spring, summer or autumn, being early in the north and getting progressively
later to the south.
-50-
The age of maturation ts generally four to six years. Rarely
it may be seven years, but generally it is five years.
There are few runs in Hokkaido, but these fish were first
introduced into Japan in 1959. In particular, eyed eggs have been
imported from America since 1968, and are continually being released in
the Yoichi River, so great hopes are entertained for the future.
Sakuramasu Cherry Salmon (Oncorhynchus masou) (BREVOORT)
This species is confined to the Asian side and is not found on
the American side. On the Pacific Ocean side of Japan, it is distributed
to the north of Kanagawa prefecture, on the Sea of Japan side to the north
of Kumamoto prefecture.
The sides of the mature adult fish show characteristic, beauti-
ful pink or red cloudy patches. This is the warmest (highest temperature
tolerance) of the salmonidae, and there is a land-locked form of a dis-
tinct colour. The land-locked form is known as "Yamabe." Many males, but
few females, remain in the rivers, and the bodies of those which go out to
sea become silver, but those that remain in the rivers have bands of a
rose-pink colour.
In Hokkaido, the upriver run is from the latter part of June to
the middle of July, and spawning occurs upstream from August to October.
One fish lays 1,000 to 2,000 eggs which hatch after eight weeks and come
to the surface after five to six weeks. They remain in the river for one
year after hatching, go down to the sea in June, and are mature in three
to five years.
