Content area
Full text
Introduction
The use of aquaculture has grown over the years with efforts channeled towards bridging the gap between demand and supply of aquatic products by culturing aquatic animals in captivity. Today the success of many aquaculture operations depends largely on the availability of a steady supply of larvae for rearing to market size (Rottmann et al., 1991). According to Adewolu & Adeoti (2010), one of the major problems identified that continually hinders the promotion and development of the aquaculture industries is the scarcity of fish fingerlings of a desired cultured species. Wild supply is fast depleting, hence this source is not capable of supplying the needed amount of fish seed for culture (FAO, 1996). Artificial propagation of the fish remains the only means to provide a more steady supply of desired fish species of good quality.
Many hormones have been researched for the purpose of controlled maturation and spawning of cultured fishes. Some are of natural or synthetic origin. The efficacy of human chorionic gonadotropin (HCG), acetone-dried carp pituitary extract, deoxycorticosterone acetate (DoCA), and Ovaprim®, fresh common carp pituitary gland (PG) has been reported by Adebayo & Popoola (2008). Breeding performance of fish using pituitary of African catfish Clarias gariepinus (Burchell, 1822) (Olufeagba et al., 1998, Olufeagba et al., 1999), Nile Tilapia Oreochromis niloticus (Linnaeus, 1758) and many other non-pisci pituitary hormones (e.g. frog) (Nwokoye et al., 2007) have also been well documented. However, little information is known about the effect of preservation of natural pituitary extract on the spawning performance of the fish.
African catfish C. gariepinus is one of the most popularly cultured and consumed fish in many parts of Africa, Asia and Europe (FAO, 1996). The artificial breeding pattern (i.e. sacrificing the male) and domestic processing method (decapitating the fish) make it a very cheap and steady source of acquiring natural inducing hormone (pituitary extract) for breeding (Fagbenro et al., 1993, Adebayo & Popoola, 2008). Considering the continuous increase in the price of synthetic hormones used in induced breeding, it is inevitable that cheaper means of artificially propagating cultured fishes need to be found. Hence, this study was designed to investigate the spawning performance of Clarias gariepinus induced to spawn using preserved (24...