Abstract
Egg adhesiveness has been a major problem affecting the hatchability of Clarias gariepinus. The removal of egg stickiness will improve aquaculture production through enhanced hatching rates. However, appropriate media for removal of adhesiveness in Catfish eggs is not yet well established. This study therefore, determine the optimum concentration and rinsing time of powdered milk (PM), Urea (UR) and Tannic acid (TA) for removal of adhesiveness of African catfish eggs and their effect on fertility and hatching success. Milt and eggs obtained from African Catfish broodstock of the same lineage were used for induced breeding following standard procedure. Four hundred fertilized eggs each were rinsed in the three different media at varying concentrations and exposure time using dry and wet fertilization methods. Treatment efficacy was assessed by comparing the percentage of non-stick eggs, fertilization, hatching and survival rate in the treatment groups and the control. Data were subjected to multivariate general linear model and Duncan multiple range tests at α0.05. Under the wet fertilization method eggs exposed to 10 g PM at 20 minutes gave the highest number of free eggs (87.50%) while 6g UR at 5 minutes recorded the lowest (27.09%). In dry method, 14 g PM at 20 minutes recorded the highest number of free eggs (90.00%) whereas, the lowest (47.50%) was recorded in 6 g urea at one minute rinsing time. The highest number of hatchlings for PM, UR and TA were 53.26%, 33.24%, and 13.13%, respectively. The survival rate was high in all treatments except in 1.5 g TA. Eggs treated with PM solution performed best in adhesiveness removal and recorded highest percentage fertilization and hatching rate. However, more studies should be conducted to establish the appropriate media for other culture fish species.
Highlights
Aquaculture is one of the fastest growing food production systems in the world with developing countries contributing significantly to its growth (Haruna, 2003)
The interaction between the rinsing concentration and rinsing time for wet method of fertilization revealed that 10 g and g powdered milk (PM) gave the highest quantity of non-stick eggs (90.00% each) at and 25 minutes, this was significantly different from other treatments (p
The fertilization rate was higher in 10 g PM at 15 minutes (95.75%) and this was significantly different from other treatment (p
Summary
Aquaculture is one of the fastest growing food production systems in the world with developing countries contributing significantly to its growth (Haruna, 2003). The culture of clariid catfish dominated local fish production in Nigeria and has grown rapidly since 1985 till because it grows fast and feeds on a large variety of food, tolerate a wide range of water quality conditions, relatively easy to reproduce in captivity and can be raised in high density resulting in high yield (Okechi, 2004). In artificial spawning, the adhesiveness of the eggs could reduce fertilization and hatching rates. Few studies have been done on how best to remove adhesiveness of the African catfish eggs in Nigeria despite dominating local fish production. Powdered milk, urea solution and tannic acid at different concentrations were evaluated
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