TECHNOLOGY FOR ARTIFICIAL SPAWNING OF
SILURUS GLANIS SPECIES – WELLS
• TECHNOLOGY DISPLAY
• Object
• The elaborated technology is after controlled spawning of
Silurus glanis – wells, towards redressing its natural
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populations and inserting it on aquaculture.
Area of implementation
Implicit costumers of spawning technology are economical
agents that have the main activity fishing and aquaculture.
• Technological system for artificial spawning of Silurus
glanis – wells
• For artificial spawning of wells having regard to special reproductive
features of species, must ensure a technical-material base specific
and in accordance with different stages of this process.
• Technological system will be apportion depending on production
capacity agreed by costumer, and will ensure by its capacity the
spawning of minimum 10 families, in order to insure maintenance
and conservation of genetic biodiversity of species.
• Correlate with the capacity for incubation, technological system will
be framed by an ensemble of earthen ponds: ponds for standingwintering, ponds for pre-maturation, modules for standing and
maturation of breeders, modules for incubation of embrionated eggs
and modules for standing and growing larvae.
• Ponds for pre-maturation,
modules for maturation of
breeders and modules for
incubation of eggs have the
same properties as the case of
pikeperch.
• For standing and rearing larvae
should be used PVC or
fiberglass tanks with volume of
about 1300 l, fitted with
proper fuel system, adjustment
and discharge of water.
DESCRIPTION OF TECHNOLOGY
• Technology for artificial spawning and rearing larvae of Silurus glanis
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involves travel along following stages:
Assurance of breeders stock;
Evaluation of phenotypic characters and sex determination;
Standing, pre-maturation of breeders;
Maturation of breeders;
Induction of sexual cells maturation;
Gathering sexual products;
Fecundation;
Incubation of sexual products in special installed enclosures;
Sampling and standing larvae in enclosure standings;
Sacking and transportation of larvae;
Rearing larvae up to 45 days.
• Assurance of breeders
stock.
• Wells breeders used in
artificial spawning come
from stocks reared in
farms especially for this
goal.
• For the establishment of
breeders stock are
chosen fish with age of 4
– 8 years and weight of 6
– 10 kg.
Morphological criteria used to
determine sex on wells
Criteria/sex
Form of
papilla
genital
Head form
Roughness
pectoral fins
of
The color of
tegument in the
ventral area
Sedimentation
erythrocytes
of
Male
Female
Concave, small
Bulging, ovoid
Slightly foursquare shape
Foursquare
Earthy
Light color
Dark
Smooth touch
Slow
Fast
• Hormonal treatment goes through after 24 hours from
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stocking of breeders in the station for incubation. For
induction of sexual cells maturation on wells, it is used
carp pituitary.
Hormonal induction of females is made in two steps:
Step I – 0.5 mg/kg of body weight for both females and
males;
Step II – 4 mg/kg of female body weight and 3 mg/kg of
male body weight.
Before injection and gathering gametes breeders are
anesthetized in a solution of 2-fenoxietanol (1 : 1000).
• Gathering eggs and artificial fertilization. Method of harvesting is
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abdominal palpation, technology known as “milking”.
Abdomen is gently massaged on longitudinal direction up and down, along
axial line of abdomen, pushing eggs by the genital hole.
From each female collect a single portion of eggs, about 160 – 200.000
eggs.
Sperm is gathered in a crystallizer by abdominal palpation or by using a
syringe with tygon tube of 5-6 cm long. Sperm is stored for 4 hours at 4
0C. Volumetrically, average quantity of sperm gather is 2.0 – 2.5 ml/kg of
body weight. Males generate between 0.13 – 0.14 × 109
spermatozoids/kg body weights.
Artificial fertilization
Fertilization is accomplished with mixture of sperm originating from at list
2 – 3 males. For fertilization of 100 g of eggs are required 2 ml of sperm.
Eggs and sperm are mixed in a fertilizing solution made by 0.3 % NaCl.
The volume of activating solution is 50 ml/100 g of eggs. Mixture is
homogenized for 10 seconds, and then, after 2 minutes add another 25 ml
of activating solution and eggs are spread on nytal frames with help of a
feather. After another 5 minutes, fertilized eggs are bringing in Nucet
hatcheries for incubation.
• Sampling and standing larvae
• Sampling of hatched larvae is made continuously on
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cushion of water, in individual tanks for gathering.
Gathering tank is fitted with a nytal cage having mesh
size of 0.3 – 0.5 mm to constrict the larvae.
The constricted larvae are sample with the help of
paddles and placed in special enclosure for standing. The
operation is carried out continuously until the end of
hatching. Counting larvae is accomplished directly at the
time collection.
Stocking density will be of 40 – 60 ex/l. flow of water in
standing tanks will be adjusted to 5 l/min. Larvae will
stay on these enclosures a period of 5 – 7 days up to
resorption of yolk.
• Growth of larvae up on achieving adult-like
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phenotypic characters
Stocking rate
Larvae achieved from each female are stoked
independently on rearing enclosures.
Stocking rate is 1500 ex/m3 and is determined taking
into account technological losses for rearing phase which
in general are estimated on 30 %.
The height of water column in rearing enclosures is
adjusted to 20 cm.
Technological water from enclosures will be assessing
physic-chemically by determination of temperature, pH
and oxygen.
The flow of water supply in enclosures for prematuration is set at 5 – 7 l/min.
• Feeding
• Rearing of larvae up to outlining phenotypic characters conformable with
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adults is achieved on account of a feeding schedule involving deliver of live
food and blended yolk of egg in first 5 – 7 days of growth and then a
composite diet composed of natural food and forage.
Feeding with natural food is achieved with very small zooplankton. The diet
is supply with blended yolk of egg.
Feeding of larvae using natural live food in a composite diet with forage will
imply the use of following feeding schedule that will allow gradually passing
to a feeding based exclusively on forage:
first 5 days: 85 % zooplankton, 15 % forage;
next 5 days: 60 % zooplankton, 40 % forage;
next 5 days: 50 % zooplankton, 50 % forage;
next 5 days: 10 % zooplankton, 90 % forage.
After that feeding will be assure only by forage.
With the passage exclusively on forage, daily ration will be determined
depending on consumption, percentage ranging from 4 to 20 % of batch
weight.
During rearing time preventive treatments are made for mix bacteria and
ichtyophtiriosis; these disease are symptoms: abatement, bleaching tail
with necrosis and then fall of necrosis part of the tail. For treatment use
oxytetracycline + neomycin.
For ichtyophtiriosis use malachite green combined with formalin.