INTRODUCTIONThe steadily growing importance of fish farming has compelled improvements in the technologies necessary for securing the initial and basic requirements for productive aquaculture; namely the production of fish seed for stocking. Fish culture today is hardly possible without the artificial propagation of fish seeds of preferred cultivable fish species. The need for the production of quality fish seed for stocking the fish ponds and natural water bodies has indeed increased steadily (Brain and Army, 1980). Artificial propagation methods constitute the major practicable means of providing enough quality seed for rearing in confined fish enclosure waters such as fish ponds, reservoirs and lakes (Charo and Oirere, 2000)

TYPES OF REPRODUCTION IN CATFISH

There are two main types of reproduction in catfish they are: Natural reproduction Artificial or Induced reproduction

NATURAL REPRODUCTION

Natural spawning is usually done without hormonal treatments. This is through the simulation of natural spawning conditions in ponds or tanks. It also occurs naturally in the wild .Some major advantages of this natural system of reproduction in catfish is that it is cost effective and it requires little or no time investment.Major disadvantages are that few of the fry survives to the fingerling stage. Another disadvantage is that the number of fertilized eggs cannot be determined.

ARTIFICIAL REPRODUCTIONThis involves the use of hormone to stimulate the egg into ovulation. There are basically two types of induced reproduction. They include semi-artificial reproduction (where the final maturation of gametes is achieved through the administration of hormones) and the artificial reproduction (where the fish are injected with hormone to stimulate ovulation and the eggs are stripped from the female brood fish manually. Fertilization is then done manually and the eggs are incubated for hatching (Akankali et al., 2011).

ADVANTAGES OF ARTIFICIAL REPRODUCTION Fish seed is guaranteed all year round Fish seed is obtained outside the normal

environment It increase the survival rate It improve quality by crossing two different parents

(hybridization)

DISADVANTAGES OF ARTIFICIAL REPRODUCTION The whole process is laborious, highly technical and

energy sapping The donor male fish is sacrifice hence loose of one

fish It a very expensive method it that it require

construction of houses and tanks

STEPS IN ARTIFICIAL REPRODUCTIONThe artificial propagation of cat fish involves a chain of activities similar to natural production. For example, the process involved in the artificial propagation of Clarias gariepinus is:→ Brood fish selection from nature or fish ponds→ Brood fish rearing→ Inducing final maturation and ovulation with hormone treatment→ Stripping of the female and egg collection→ Artificial fertilization→ Incubation and hatching of eggs; and→ Larvae and fry rearing.

Plate 1: Show the female brood stock strip for egg collection.Image Source: Google images

PROCUREMENT OF SPERMThe spermatozoa from a male spawner fish are obtained an hour to stripping. It is difficult to strip the male for milt. This is probably due to the anatomical structure of the seminal vesicles. Therefore, milt is obtained by sacrificing a spawner male fish. Its testes are dissected and small incisions are made into the cream colored lobes of the testes. The milt can easily be squeezed out and collected into a vital or small bottle. This process can obtain several droplets of milt. Milt can be diluted with physiological saline solution. Contact with water should be avoided. Otherwise, the spermatozoa lose its ability to fertilize mature fish eggs. Milt solution can be stored in a refrigerator for one or two days without affecting its activity (Nwadukwe et al., 1991).

Plate 2: Show the male brood stock sacrificed for sperm collection.Image Source: Google images

COMMON HORMONES USED IN INDUCED REPRODUCTION

OVAPRIM Human Chorionic Gonadotropin (HCG) Carp Pituitary Extract (CPE) Leutinizing Releasing Hormone

FERTILIZATIONThe union of the male’s spermatozoa and the female’s mature eggs to form a zygote is referred to as fertilization. In fish, the fertilization period is limited. This is because; fish eggs swell immediately when in contact with water, resulting in the micropyle closure. For common carp, the fertilization period is within 45-60sec. In most other fish species, it is limited to few minutes. Special precaution must therefore be taken to the application of water during artificial fertilization. Three methods are commonly adopted in the artificial fertilization (Akankali et al., 2011).

Plate 3 Showing an incubator where eggs are incubatedImage Source: Google images

CONCLUSIONIt has been stated that Nigeria is a protein deficient country. Fish stands as a cheap source of animal protein. In order to make fish (and protein) readily available, artificial reproduction, through which maximum production is usually achieved, should be encouraged so as to meet the high demand for fish and protein in general in the increasing population.

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