By Ruby Gonzalez
Striking the right balance between darkness and light enhances the viability of hybrid catfish Heterobranchus bidorsalis x. Clarias gariepinus in its early life stage, according to a study conducted in Nigeria, where catfish is the leading aquaculture product.
By Ruby Gonzalez
“Exposing fertilized eggs to continuous light worsens hatchability, while longer darkness exposure reduces survivability of fish larvae,” cited Dr. Isreal Adebayo, a senior lecturer at the Department of Fisheries and Aquaculture Management, Ekiti State University, in his research article published in the HSOA Journal of Aquaculture and Fisheries.
Adebayo suggested that two different lengths of light exposure are needed to achieve balanced results in terms of hatchability of eggs, growth and survivability of fish fry.
Incubation and hatching of eggs should be done under complete darkness, while rearing of fry should be done under equal light and darkness exposure, he said.
The highest hatchability of eggs and optimum growth performance of hatchlings were observed under 24-hour darkness, but survivability was reduced due to cannibalism.
The research further showed that larvae of hybrid catfish were photophobic.
While the highest growth performance was recorded at complete darkness, deformed fish larvae were equally highest compared to other photoperiod regimes. He said this could be related to another study which asserted “that fish species exposed to incorrect hour of photoperiod could be severely crippled and may not develop properly.”
The hybrid catfish was produced through hormone-induced spawning.
Artificial insemination of catfish using hormonal induction method appeals to the farmers as a cheap and practical approach producing “highly reliable” fingerlings, the report said.
The establishment of the appropriate photoperiods for the artificial propagation of hybrid catfish is expected to contribute to the growth of aquaculture in Nigeria.