Abstract
There has been a nationwide unexplainable huge loss of fish at the fry/fingerling juvenile stage since 2013 by catfish breeders or fish farmers in Nigeria. This has prompted search for the probable causes for the huge losses during these stages. The systematic elimination of the probable causes of the massive mortality of fish fry/fingerlings, by the practicing farmers and the concerned supervising authorities, has been narrowed down to inbreeding of catfish. This has come with different narrations of woes ranging from a great reduction in hatching of catfish, to table size production. Inbreeding in fish is said to be the mating of closely related individuals leading to loss of hybrid vigor. It has made hatching unpredictable because most brood stocks in the country have lost hybrid vigor. The genuine concern for the loss to hatchery operators led to a concerted effort of a group of fish farmers from different geo-political zones of the country, other professional career civil servants, coming together to exchange notes on practical experiences and findings on their farms. This has continued to date. The general observation from empirical experience of hatching Clarias gariepinus was that on hatching, there will be growth but indiscernibly slow, active, and showing promises of potential fingerlings/juveniles. However, between 3rd and 4th week the fry will suddenly die in large numbers and within six weeks, the mortality is complete. This was termed by one of the farmers as the asymptomatic third week syndrome of Clarias gariepinus fry.
The other consequences of inbreeding can be summarized as follows: the slow growth of the fish, taking longer days to reach market size of an average of 700g to 1kg; slow conversion ratio of feeds; percentage runts are high; low immunity to infections; low returns on investment if not total capital loss; high flux of fish farmers. The difficulties in importation of fresh catfish brood stocks as juveniles from other countries especially Holland, South Africa, and Indonesia to improve the hybrid vigor led to inbreeding. Old stocks are being re-circulated. The degree of inbreeding depends on the filial generation of the male and female brood stock crossed which is not known by most breeders. The filial generation of the catfish brood stock being sold and transferred between farms and geopolitical zones of the country became unknown. The F generations of the brood stock in the country is undetermined and remain indeterminate. The challenge has persisted with farmers looking for alternative ways to resolve the issue of inbreeding. Time is fast approaching that none can hatch. The co-author of this paper wrote a petition to the then Chairman Senate Committee on Agriculture and had discussions at different levels on this issue. This paper provides possible solutions to resolving problems associated with inbreeding in catfish farming in Nigeria. These are the short-term solution which is the immediate importation of fresh brood stock and on the long run, the establishment of a national brood stock bank.
Keywords: Inbreeding, Clarias gariepinus, fish farmers, consequences of inbreeding, mortality, short -term and long -term solutions