INTRODUCTION CHILLING AND ITS EFFECT ON THE EGGS OF CLARIAS

INTRODUCTION Tobor (1985) stated that protein of animal origin is in short supply in Nigeria as increase in livestock population is being limited by several causes including virus diseases, scarcity, drought and high cost of feeds and low genetic potential of The Effect of Cold Storage of Clarias gariepinus Sperm on Hatchability and Survival Akinyemi, A.A. et al indigenous livestock breeds. This situation has given rise to considerable increase in the demand for fish to supplement animal protein. Also, FAO (1996) revealed that West Africa countries of which Nigeria is one, obtain at least 50 percent of their animal protein needs from fish and fish products. According to Aromolaran and Akintunde (1998), the residents of Warri, in Nigeria preferred and actually consumed it more frequently than any other animal protein source. The average household in the area consumed fish at least once a day for 16days in one month. The number of species in aquaculture is growing and several important species rely on the collection of broodstock or seed from natural population. With these present facts, it is very important that the aquaculture sector should be able to meet the challenges posed on the demand for fish to supplement animal protein. One way of achieving this, is by improving genetically on our broodstock (i.e. sperm management). The collection of fish sperm for storage (sperm management) is a good technique that may perhaps also improve the aquaculture sector. Spermatozoa motility (time of their motion after activation) is very important for successful fertilization of the eggs (Jezierska and Witeska, 1999). Thus together with morphologic characteristic, is considered an indicator of milt quality. Sperm motility and their ability to fertilize eggs are highest just after stripping (Jezierska and Witeska, 1999). In case of artificial spawning, storage of milt is sometimes necessary. Reduction of spermatozoa quality (their ability to fertilized eggs) with time is well known, but there are little detailed data on motility time reduction. [Goodall et al (1989); Gluchoska and Jezieka (1994), and Jezierka et al (1995)] showed the effect of storage on motility time, while Ravinder et al (1997) on the percentage of spermatozoa motile after activation. According to Sarnowski et al (1997), however storage of sperm for 5hours in the refrigerator of about O0C did not adversely affect fertilization rate. Possibility of milt storage at about O0C was proved by [Babiak and Glogowski (1996); Hulat and Rothbard (1979); and Malczewski (1988)]. The authors observed that sperm stored at that temperature was able to fertilize eggs. However, storage affects sperm motility time. It seems that temperature of activating medium may affect activity of spermatozoa. Goodall et al (1989), and Babiak and Glogowski (1996) showed that at lower temperature time of motility is longer. Techniques of sperm management have been established in some freshwater fish species such as cyprinids (Billard, Cosson, Crim & Suquet, 1995) or Siluroids (Legendre, Linhart & Billard, 1996) and in Salmonids (Scott & Baynes 1980, Billard, 1992). Among . At O0C conditions, spermatozoa can be stored for a few hours up to several days, depending on the species while cryopreserved gametes can be theoretically stored between 200 and 32,000 years without deleterious effect (Ashwood-Smith, 1980). The use of cryopreserved spermatozoa can be delayed from the data of ova processing. The aim of this present study was to evaluate the effect of the hours of cold storage of Clarias gariepinus sperm on hatchability and survival.