Masters Thesis
Predators affect aquaculture by feeding on fish, causing injuries and spreading diseases. Questionnaires were administered to 137 fish farmers in Kirinyaga County assessing farming practices, constraints, type of predators and extent of predation experienced by fish farmers. Prevalence of parasites was evaluated in 289 fish (203 tilapia, 86 catfish) and 50 piscivorous birds in the region. Tilapia, catfish and ornamental fish were the main species of fish farmed. Overgrown vegetation, low water levels and poor predator control methods were the main management constraints observed. Low quality and expensive feeds, water scarcity, predation, theft and lack of proper markets were major fish production constraints. Piscivorous birds (Herons, kingfisher, ibis, hamerkop), otters, monitor lizards and snakes were the main predators encountered. Predators were controlled by fencing (10%), pond netting (21%) and chasing them away (74%). Tilapia (39%) and catfish (45%) from earthen ponds were infested with at least one species of helminth parasite. Farms which had higher presence of birds also had more parasitic infestations. Prevalence of parasites isolated in tilapia were; Acanthocephala spp. (11%), Clinostomum spp. (5%), Dactylogyrus spp. (3%) and Diplostomum spp. (22%). In catfish, they were; Acanthocephala spp. (4%), Contracaecum spp. (24%), Dactylogyrus spp. (5%), Diplostomum spp. (11%), Gyrodactyrus spp. (6%) and Paracamallanus spp. (16%). Water birds including herons, cormorants, kingfishers, hamerkop, spoonbill and several stilts were infested with Clinostomum spp. (4%), Contracaecum spp. (2%), Acanthocephala spp. (16%), and cestodes (36%). Genera of parasites with documented zoonotic importance isolated from fish and predatory birds were; Clinostomum spp., Contracaecum spp. and Acanthocephala spp. Predation has a significant role in aquaculture profitability. Most farmers don’t practice effective predator control methods due to inadequate knowledge on losses impacted and ability of predators to spread diseases in aquaculture. Farmers should be trained and advised on handling and cooking of fish to avoid contracting zoonotic parasites.
Norwegian Agency for Development Cooperation (NORAD)