TECHNOLOGY FOR ARTIFICIAL SPAWNING OF TINCA TINCA SPECIES – TENCH

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TECHNOLOGY DISPLAY Object

The elaborated technology is after controlled spawning of

Tinca tinca

– tench, towards redressing its natural 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 tench Tinca tinca –

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 standing wintering, ponds for pre-maturation, modules for standing and maturation of breeders, modules for incubation of embrionated eggs and modules for standing and growing larvae having the same technical parameters as like as for wells.

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DESCRIPTION OF TECHNOLOGY

The technology for artificial breeding and rearing of larvae imply the passing through of following phases: Assurance of breeders stock; Tinca tinca 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; Sacking and transportation of larvae; Rearing larvae up to 45 days.

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Assurance of breeders stock.

Tench breeders used in artificial spawning come from stocks reared in farms especially for this goal or captured from natural environment. In autumn, breeders are catch from rearing ponds and populated on wintering ponds. Most times, tench breeders are wintering together with other cyprinids. For establishment of breeders stock are chosen fish with age of 3 – 6 years and weight of 0.8 – 2.0 kg.

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Evaluation of phenotypic characters and sex determination

Tench breeders are catch from wintering ponds and separated depending on sex when water temperature attains 15 – 18 0C. Separation on sexes is accomplish easily, breeders exhibiting a pronounced sex dimorphism: male display an acute development of pelvic belt and of fins from this level, with bowing and bodying up on a part of fins, and also males are bigger than females.

For artificial spawning are used breeders having average body weight between 800 – 1500 g/ex on females and between 1500 – 2000 g/ex on males.

Breeders are hold in maturation ponds up on the moment when water temperature attain and remain around the value of 22 – 24 0C and don’t fell under 19 – 20 0C in the night.

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Induction of sexual cells maturation

When water temperature is maintain around 22 0C, breeders, mails and females are catch from maturation ponds and stock in standing modules from incubation station.

Hormonal treatment goes through after 24 hours from stocking of breeders in the station for incubation. For induction of sexual cells maturation on tench, it is used carp pituitary. The total dose is of 10 mg/kg of body weight on females and 6 mg/kg of body weight on males.

Males are stimulated with a single dose of 6 mg/kg body weight.

Hormonal induction of females is made in two steps: Step I – 3 – 4 mg/kg of female body weight; Step II – 6 – 7 mg/kg of female body weight.

Injection is applied within the peritoneum. On temperatures of 23 – 25 0C, breeders are injected in the evening time, dealing the first dose on females and entirely amount of hormone on males. The second dose on females is deal at an interval of 8 – 10 hours.

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Gathering eggs and artificial fertilization.

Gathering eggs is made by gently palpation of abdomen.

Females release the eggs in one or more portions. From one female are gathering between 50 and 150 g of eggs. After gathering eggs, one gram of eggs are weight and then counter to determine absolutely fecundity (number of eggs / female) and relative fecundity (number of eggs / kg of female). One gram coincides with about 1400 eggs.

The same proceed with males; sperm is gathered in a crystallizer by abdominal palpation or by using a syringe with tygon tube of 5-6 cm long. The tube is placed slowly in the urogenital outlet. At the exemplars whereat the permeation is complete, sperm start to flow on syringe when primer is move back.

Volumetrically, the average quantity of gathered sperm is of 2.0 – 2.5 ml/kg of body weight.

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Artificial fecundation

Eggs gained from each female are fertilize with a mixture of sperm from more males. For fertilization of 100 g of eggs are required 2 ml of sperm. Fertilization is made by dry method. Sperm is dispersing on eggs, after that, the mixture is homogenized for about 2 minutes. The fertilized eggs are spread on frames and after another 5 minutes, fertilized eggs are bringing in Nucet hatcheries for incubation.

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Incubation of sexual products

Incubation of eggs will start with introduction and attach of frames in the Nucet hatcheries. Incubation lasts 2 – 3 days at the temperature of 23 – 25 0C.

For tench, optimal temperature for hatch is 23 – 25 0C.

During embryogenesis the flow of water supply for incubation enclosures will be correlated with physiological necessities of embryo in its different development phases.

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Sampling and standing of larvae

Sampling of hatched larvae is made continuously on cushion of water, in individual tanks for gathering. Gathering tank is fitted with a nytal cage having mesh size of 0.2 mm to constrict the larvae.

The constricted larvae are sample with a standard measure and placed in other clean hatcheries, where are hold up on the resorption of vitelline bag, about 5 days at 24 – 25 0C.

Stocking density will be of 20 – 25.000 ex/incubator. Water flow in tanks for standing of larvae will be adjusted to 5 l/min.

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Growth of larvae up on achieving adult-like phenotypic characters Stoking rate

Larvae achieved from each female are stoked independently on rearing enclosures.

Stoking rate is 10.000 ex/m3 and is determined taking into account technological losses for rearing phase which in general are estimated on 30 %.

Preparing of rearing modules and stoking of larvae.

Preparing of rearing enclosures is made with 48 hours afore stoking.

Enclosures are rigorously cleaned with Germostop solution 10 %, this solution is keep on for an hour and then banished by repeated wash off.

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 pre-maturation is set at 5 – 7 l/min.

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Feeding

Rearing of larvae up to outlining phenotypic characters conformable with 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.

For tench rearing shall be used carp feeds with a content of crude protein ranging from 35 to 45 % and granulation of 0.1 – 0.2 mm. Feeds shell be delivered in 8 – 10 meals per day.

The growth gain that has to be achieved after 30 days, up to outlining of adult-like phenotypic characters, is 300 – 500 mg/ex.

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Terms of maintenance on rearing time

On the rearing enclosures must be keep a severe sanitation. The sanitation will be achieved before every feeding and will consist of removing excrements and any offal of feeds from the last meal. At least once every 24 hours to clean the walls of rearing enclosure through rubbing them with a sponge flooded in a solution of potassium permanganate with a concentration of 23 mg/l. Also can be used methylene blue on a concentration of 1 %.