Nile tilapia remains to be one of the most preferred fish for rearing and human consumption in Africa . Despite being a prolific breeder, the demand for tilapia seeds remains high, and hatcheries have been established to meet this demand . However, hatcheries face significant challenges with high costs associated with feed , electricity, and also with fish diseases. An often overlooked challenge in the hatcheries is the presence of ectoparasites which pose a high potential risk to fish health. The combination of high stocking densities in most hatcheries and frequent handling of the fish, increases the susceptibility of the fish to ectoparasites infestation.
A study was conducted in two hatcheries in Homabay County, Kenya in the months of March and April, in a bid to establish the prevalence and intensity of different ectoparasites in these facilities.
Samples were collected from all age groups in the two hatcheries and examined in-situ. Twenty (20) scoops each for eggs, fry and larvae were sampled, while for broodstock and fingerlings 40 samples each were taken, totaling to 140 samples. The eggs , larvae and fry were examined wholly under the microscope, while for fingerlings and brooders, skin scrapes, fin clips and gill clips were examined. The total parasitic prevalence was 66% (92/140) and prevalence was highest in broodstock fish at 80% (32/40) while it was lowest in larvae at 10% (2/20).
Five ectoparasite genera were recovered, with Gyrodactylus spp. being found in all age groups at an overall prevalence of 35% (49/140).The o thers included the genera Dactylogyrus spp.12% (19/140) , Trichodina spp. 11 % (16/140), Epistylis spp. 4% (6/140) and Argulus spp.0.7% (1/140) (Table:1 ). The highest mean intensity was observed in the ciliate, Epistylis spp., at 30.8.
The findings show that ectoparasites can be found in all the age groups in the hatchery , and being most prevalent in brooders , they can spread to other age groups. Hatchery owners should implement strict biosecurity measures in order to avoid the spread of ectoparasites within the hatcheries and grower ponds.