Ethiopia covering a surface area of 1127127 sq km is blessed with rich water resources in the form of large lakes (Crater and Rift Valley), reservoirs, lengthy rivers and small water bodies with a water expanse of about 8800 km2 and rivers at a length of 7185 km. The country depends largely on inland water bodies for fish production and livelihood. Considering the rapid increase in human population which was just 70 million in 1970s has increased to over 110 million in 2018. This rapid increase in human population forces Ethiopia to identify additional food production sectors and it is in this context, fisheries and aquaculture plays a significant role. Ethiopia must therefore concentrate more on fish production through capture and culture fisheries. Although rich in water resources and fish species diversity which is more than 200, Ethiopia now bestow interest in the exploitation of only two major fish species namely Nile Tilapia, Oreochromis niloticus and the African catfish, Clarias gariepinus from natural water bodies. Recent reports indicate that owing to over dependence, both Nile Tilapia and Catfish populations are over exploited and thus the population of both species are depleting rapidly in lakes and reservoirs. Besides over exploitation, other factors such as excessive infestation of aquatic weeds particularly water hyacinth and disease prevalence in fish species affect fish production and productivity in most lakes in Ethiopia.
The rapid spread of water hyacinth in water bodies has become a subject of great concern in Ethiopia. Weed infestation in Lakes of Ethiopia is a recent history, and the available reports indicate that water hyacinth started spreading first in Lake Tana and thereafter its infestation has been reported in a number of lakes. Several studies reported the negative consequences of water hyacinth to the lentic ecosystem, human health and fish production. Another major factor receives the attention of scientists is the prevalence of diseases in cultivable fish species. From a perusal of literature, it is seen that some studies were concentrated on the incidence and prevalence of metazoan parasites which are of great economic importance. Besides metazoan parasites, research activities were also focused on microbial diseases especially bacterial diseases in Nile tilapia, Catfish, and to some extent the common carp, Cyprinus carpio.
The present paper describes the extent of infestation of water hyacinth in lakes of Ethiopia and its impact on lake environment particularly water quality parameters and contributing factor for the incidence of infestation of parasites in fish species. The paper also elaborates the susceptibility of commercial fish species to various kinds of parasites and pathogens and their impacts on the health of fish and fish production. As lakes are the life and life management systems of millions of rural people, the paper suggests ways and means and action programmes to protect the lakes from such devastating impacts of water hyacinth and fish diseases to create a sustainable environment to enhance fish production to ensure food security.