Ecological Position of 'Small Barbs' and Their Potential for Fisheries: An Option to Reduce Fishing Pressure on 'Large Barbs' of Lake Tana (Ethiopia)?

The two barbs, Barbus humilis and Barbus tanapelagius are important pelagic fish in Lake Tana. These ‘small barb’ species (<10 cm fork length) play a key role in the Lake's ecosystem as a link between zooplankton and the top predators, mostly ‘large barbs’. This paper presents an overview on the position of ‘small barbs’ in the food web of Lake Tana as indicated from gut content analysis. Barbus tanapelagius, the most abundant and specialized species, exploited zooplankton. Barbus humilis mostly fed on detritus and zooplankton. Barbus tanapelagius, and to some extent the benthopelagic Barbus humilis, transferred energy from zooplankton to the top level of the food web. Barbus humilis is a vector of energy and biomass from detritus to top predators. Pelagic fisheries are proposed as an option to reduce fishing pressure on the endemic species flock of ‘large barbs’. If, however, a fishery on the ‘small barbs’ is proposed to increase the sustainable yield, implications on the ecosystem balance should be critically assessed. Regulations should be recommended for these fisheries (gear, habitats and season) accounting for the biological constraints.