FR2778063A1 - Rearing procedure for aquatic creatures, especially freshwater catfish - Google Patents

Abstract

The procedure, in which the creatures are reared from egg stage to the selection of mature adults for breeding, consists of maintaining a constant water temperature in the hatchery, at least from the larvae stage, and in the rearing ponds, as close as possible to the biological thermal optimum for the creatures being reared, i.e. 26 deg C for Siluris Glanis. In the hatchery, the creatures are raised on solely artificial feed, while in the rearing ponds a nomination of natural and artificial feed is used. Before the incubation stage, a rigid support, e.g. of wire mesh, is placed in the incubation tank prior to introducing the eggs so that the eggs can attach to it individually. During the incubation process the support can then be removed from the tank to subject the eggs to a temperature shock and prevent larvae hatching from eggs which have undergone an overlong embryogenesis, leading to poor performance.

Description

REPRODUCTION AND BREEDING PROCESS IN AN AQUATIC ENVIRONMENT

  IN PARTICULAR OF SILURUS GLANIS AND A DEVICE FOR ENABLING

TO IMPLEMENT IT

  The present invention relates to the fields of aquaculture and fish farming and in particular the adaptations and the means which make possible the reproduction and the breeding, under optimal conditions of the different species living in aquatic environments such as

  for example fish, crustaceans, molluscs, etc.

  The serious shortcomings of aquaculture and fish farming methods, as currently practiced, are well known. They result in difficulties in terms of the quality and image of the productions and have negative consequences in terms of their marketing. They are mainly manifested in the breeding lines and in the management of the corresponding biotopes often designed and produced, in search of increased productivity, in contradiction

  with the basic requirements of biology.

  The constraints and the drifts resulting from the intensification as regards aquaculture and fish farming productions commonly lead to confining with significant densities - the subjects raised in basins of the artificial type - in concrete or in "plastic" materials, etc ... - or in cages immersed in ponds or at sea, thus depriving them of normal contact with the natural adversity that the species concerned must face, in particular

  at the bacterial, parasitic, etc. levels

  The establishment and development of immune defenses are greatly disturbed or inhibited in the subjects concerned, thus creating a situation of dependence on the means of veterinary pharmacy and more particularly, antibiotics often incorporated directly during their manufacture in the composition of foods usually distributed. -2- This situation of dependence is, moreover, aggravated by the systematic recourse to an entirely artificial diet whose industrial production cannot ensure a perfect continuity of the qualitative data, nor avoid, as a result, the appearance of deficiencies often with the origin of system failures

immune system or their worsening.

  These negative aspects of conventional, and in particular intensive, forms of aquaculture and fish farming regularly observed in the growth phases of fry and juveniles towards their commercial sizes take on a much more significant significance, by their consequences, in the

  larval reproduction and breeding phases.

  Indeed, the gametes of spawners selected among the subjects bred according to the conventional modes described previously do not have the high level of biological quality of the gametes of spawners living in natural conditions or in conditions of type

  natural, especially in the yolk of the oocytes.

  Embryogenesis and larval life are strongly affected, leading, in this situation also, to very early recourse, i.e. from the phase

  incubation, using veterinary pharmacy.

  This situation leads to a weakening of new subjects, initiated from the egg and the embryo, thus creating

  conditions for a permanent impairment.

  In addition, certain aspects of the commonly used reproduction protocols, particularly for freshwater fish, further accentuate the initial state.

  biologically deficient in the embryo and larva.

  Indeed, during fertilization and incubation manipulations, to prevent the eggs from sticking together and sticking together - which they would do naturally but would mostly lead them to perish by default of oxygenation - it is practiced - 3 - their "takeoff" by means, in particular, of enzymes

  proteolytics added to the water in the incubator.

  These products combine their effects with those of fungicides, antiparasitics, bactericides, commonly used in a conventional manner during incubation. This results in a more or less significant deterioration depending on the doses used of the membrane of the eggs, detached and moving in the incubator, at the time when its role, in particular in the oxygenation of the embryo, must, on the contrary, be favored. In addition, the detached eggs float in the incubator where they are needlessly continuously shaken; their control, such as the observation of embryogenesis in progress, is then very difficult

otherwise impossible.

  On the other hand in semi-artificial aquaculture, it is sometimes planned to place in the spawning areas, nests made of branches in order to recover the eggs;

  nests that can then be placed in the incubators.

  One of the methods intended to potentiate the results of aquaculture, in particular in terms of growth of the subjects bred for their marketing, consists in making reproduction activities impossible and therefore preventing seasonal maturation.

successive after puberty.

  One of the ways to make it impossible for the breeding activities of high subjects, obtained for

  of salmonids, is to make them triploid.

  The triploidy which naturally exists in an exceptional way in aquatic environments corresponds to the presence in the nucleus of the cell of three identical chromosomal batches - each representing the genetic inheritance of the subject - instead of the two identical chromosomal batches which define diploidy,

normal situation of the cell.

  - 4 - Triploidy is not genetic manipulation; the chromosomal group representing the genetic heritage is not affected and remains identical whether the same subject is triploid or diploid. The triploid subject is therefore normally sexed but it is sterile. In the absence of reproductive activity, all of the energy consumed by the high subject will be devoted to its growth which will therefore be much faster than that of the same diploid subject: the productivity of aquaculture

is greatly increased.

  Triploidy also makes it possible, through the resulting sterility, to fully control the demography of the species concerned; it thus makes it possible to introduce it into the natural environment, in particular for ecological purposes, without running the risk of losing control of its population and of dangerous proliferation; this takes on a particular meaning when it is, for example, a very large predator, as

Silurus Glanis.

  In addition, triploidy eliminates the risk of genetic pollution and authorizes the use of the species concerned for ecological purposes or aquaculture in areas where it is not naturally present and

  o it is therefore not part of existing ecosystems.

  In all these situations, the necessities of the struggle for the preservation of natural species and for the safeguarding of ecosystems lead to administrative attitudes and regulations prohibiting the introduction and use of diploid subjects of the foreign species concerned. In the case of Silurus Glanis for example, naturally present in the continental parts of the temperate zone in Europe and West Asia, the triploidy of the species allows its introduction and use, technically and administratively, by others climatic zones, for example warm temperate, subtropical, tropical, -5

equatorial, etc ...

  One of the known methods for obtaining triploidy consists in applying a thermal shock to the egg; this thermal shock must be carried out under specific conditions, at a specific time, at a temperature

  given and during a determined time.

  One of the consequences of the thermal shock is to deteriorate relatively the treated egg in particular at the level of the yolk and to have, therefore, a negative effect on

embryogenesis.

  The conditions of maturation, reproduction, incubation in conventional aquaculture considerably amplify these difficulties, to the point of making triploidy inaccessible for most commercial species - except for salmonids - and to obtain it only with random triploidy rates by

report on the subjects treated.

  It is therefore in a sort of negative spiral that the shortcomings of conventional aquaculture and fish farming are seen by reinforcing each other both at the level of the growth stages of fry and juveniles towards their commercial sizes and at the generation level. - maturation of broodstock, reproduction, larval breeding of future subjects intended for enlargement and the pursuit of

generation itself.

  The present invention provides a solution to the shortcomings of ancient art (or practice

  conventional) mainly on the points described.

  It achieves this by avoiding or eliminating the contradictions between the farming processes and the ordinary natural constraints of biology, and on the contrary by developing, normalizing and potentiating the natural means which nature often has only one way discontinuous and / or random. -6- The reproduction and rearing process on which the invention is based is of the type comprising that of the following conventional phases: - hatching, vesicular resorption, different stages of larval rearing, rearing up to stage d hatchery or juvenile in hatchery, - growth and enlargement in tanks, - transition from the fry phase or from the juvenile phase to the adult phase, - selection of broodstock, maturation, - oocyte and sperm collection, - fertilization,

- embryogenesis in an incubator.

  According to the main characteristic of the invention, the aquaculture process is remarkable in that it consists in placing in the incubator, before the introduction of the eggs, a removable support accommodating them on reception areas provided for this purpose. at the time of their

introduction into the incubator.

  This support has the advantage of allowing the individual fixing of the eggs which are thus immobilized throughout the duration of the embryogenesis each being perfectly exposed to the circulation of water in the incubator and

  this fact in particular benefiting from optimal oxygenation.

  The individual fixing of the eggs on the support prevents them from sticking together and therefore perish for the most part due to insufficient oxygenation and makes it unnecessary to add products to the incubator to water. proteolytic enzymes, intended specifically for conventional aquaculture to separate them

after they have gathered.

  In addition, the eggs being fixed and immobilized and no longer unnecessarily in motion for the duration of the incubation, embryogenesis can be observed and

  continuously monitored, especially in its final phase.

  Another particularly interesting characteristic of the process of the invention consists in removing from the incubator the removable support on which the eggs are individually fixed so as to interrupt the incubation process at a determined time and thereby avoid hatching of larvae whose embryogenesis would have

too long.

  Indeed, the duration of embryogenesis within an incubation operation is more or less variable depending on the eggs and the larvae whose embryogenesis would have been too long are less efficient. Their elimination, before hatching, greatly limits the size dispersion and leads to much more homogeneous production batches, thus significantly improving productivity in quantitative terms

and qualitative.

  Another particularly advantageous characteristic of the process of the invention consists in placing said removable support, after its removal from the incubator, in a different temperature zone so as to cause a thermal shock on the eggs before the first cell division; the application of a thermal shock, different according to the species concerned, makes it possible to obtain triploid subjects. According to a nonlimiting exemplary embodiment, for Silurus Glanis, it is

cold shock.

  The advantage of the removable support is that it allows all the eggs to move to the different temperature zone at the same precise moment and ensures exposure to thermal shock of the same duration for

  the set of eggs and each one of them.

  Thus, once defined, the three parameters varying according to the species raised and treated which are the moment of intervention, the temperature of the thermal shock and the duration of application of said shock will be identical for all the eggs and each of between them. Of course, the objective of homogeneity of treatment upstream and -8 during triploidy is to produce one hundred percent of triploid subjects, without risk of accidental diploidy which would raise the problem of genetic pollution and

livestock management.

  The invention also relates to the device making it possible to implement this method and remarkable in that the aforesaid removable support consists of a rigid lattice formed of a frame whose general shape adapts to the interior shape of an incubator of

  so that it can be introduced.

  According to a particularly advantageous characteristic of the invention, the trellis is formed by two circular frames linked together by vertical uprights so that the centers of the two circles are on the same axis forming a rigid frame the vertical uprights and the circles serving as a support and attachment point for crisscrossing wires and passing through each upright so as to produce a condensed trellis inside the chassis allowing the eggs to be fixed there

after fertilization.

  The choice of a wire as a support for fixing eggs is particularly advantageous in that it allows fixing on a small part of the membrane, the rest of the spherical surface of the egg ensuring

oxygenation.

  According to a non-limiting characteristic of the invention, the wires constituting the trellis have a diameter less than the diameter of the eggs to which they

serve as support.

  According to another particularly advantageous characteristic of the invention, the rigid frame as well as the wires are made of rot-proof material which optimally conducts the temperature to which they have been subjected in order to guarantee very high homogeneity in the heat treatment which is carried out. undergo eggs

remained attached to the support.

  -9- Of course, said rigid mesh is provided with a gripping member allowing it to be removed from the incubator, placed in the different temperature zone and returned to the incubator manually or by any lifting means. It is understood that the method and the device which have just been described above, were for the purpose of disclosure rather than limitation. Of course, various arrangements, modifications and improvements can be made, without departing from the scope of the invention taken in its broadest aspects and spirit. Thus, the biotope to which the process applies is not limited to freshwater but to all

  situations where aquatic life is possible.

- 10 -

Claims (6)

  1. Reproduction and rearing process in an aquatic environment of the type comprising that of the following conventional phases: 5 - hatching, vesicular resorption, different stages of larval rearing, rearing to the fry or juvenile stage in hatcheries, - growth and enlargement in basins, - passage from the fry phase or from the juvenile phase to the adult phase, - selection of broodstock, maturation, - oocyte and sperm collection, - fertilization, - embryogenesis in incubator, CHARACTERIZED IN THIS 'It consists in placing in the incubator, before the introduction of the eggs, a removable support accommodating them on reception areas provided for this purpose at the time of their introduction into the incubator. 2. Method according to claim 1, CHARACTERIZED IN THAT it consists in removing from the incubator the removable support on which the eggs are individually fixed so as to interrupt the incubation process at a determined time and thereby avoid l hatching of larvae whose embryogenesis would take too long.25 3. Method according to claim 1, CHARACTERIZED IN that it consists in placing said removable support, after its removal from the incubator, in a different temperature zone so as to cause a thermal shock on the eggs before the first cell division .30 4. Device for implementing the method according to claim 1 of the type which consists in placing in the incubator, before the introduction of the eggs, a removable support accommodating them on reception areas provided for this purpose at the time of their introduction into the incubator, CHARACTERIZED BY THE FACT THAT it comprises a removable support constituted by a - he -   rigid lattice formed of an armature whose general shape adapts to the interior shape of an incubator   so that it can be introduced.   5. Device according to claim 4, CHARACTERIZED BY THE FACT THAT the trellis is formed by two circular frames linked together by vertical uprights so that the centers of the two circles are on the same axis forming a rigid frame the vertical uprights and the circles serving as support and attachment point for the intersecting wires and passing through each upright so as to produce a condensed trellis inside the chassis allowing the eggs to be fixed there after fertilization.   6. Device according to claim 5, CHARACTERIZED BY THE FACT THAT the rigid frame as well as the wires are made of rot-proof material optimally conducting the temperature to which they have been subjected in order to guarantee a very high homogeneity in the heat treatment   that is subjected to the eggs that remain attached to the support.