Domestication of Chrysichthys Nigrodigitatus of the Cross River, as an Adaptation to Climate Change and a Boost for Aquaculture Expansion in Nigeria

Chrysichthys nigrodigitatus, commonly known as silver catfish, is a prized food fish in Nigeria. It occurs in several African rivers. In the Cross River system, it occurs all year round with peak in the rainy season, from April to October. Several studies have reported on some threatening factors to the species’ survival, including overfishing, low genetic diversity and climate change. The proposed method to curb the depletion of the resource is domestication. Studies were conducted to determine the reproductive ecology of the species. Simulation of these ecological factors in the hatchery for possible domestication of the species was carried out. Results show that the species is a freshwater species with salinity range from 0.01-0.06 ppt. Their preponderance was directly correlated with turbidity and indirectly corelated with transparency, showing that they prefer dark and shaded conditions. Rainfall triggered reproductive activities. Spawning occurred within the rainy period in crevices and holes in the rocky substratum of the river bed. We simulated these conditions in the hatchery and fish farm by placing cylindrical pipes as holding receptacles in the ponds. This provided hiding place and shade for them. Spawning inside the receptacles was observed in the month of June through September, coinciding with the phenomenon in the wild. The species is shown to embark on parental care. The male parents carry the brood in their mouths until they were able to fend for themselves. Thus, understanding the reproductive ecology of Chrysichthys nigrodigitatus in the river, enabled us to develop protocol that assisted in its domestication. This is the first time Chrysichthys nigrodigitatus has been raised in the hatchery and made to spawn in captivity. Thus, our work has expanded the aquaculture range in Nigeria and Africa.