The piscivorous barbs of Lake Tana (Ethiopia): Major questions on their evolution and exploitation

This paper surveys some major questions on the evolution of eight piscivoro us Barbus species (B. acutirostris, B. dainellii, B. gorguari, B. longissim us, B, megastoma, B. platydorsus, B. truttiformis, and B. macrophtalmus), w hich together with six other species compose the endemic hexaploid 'large b arb' species flock of Lake Tana. Preliminary data suggest that the major pr ey species of these piscivores (up to 90 cm length), in contrast to previou s reports, is not Barbus trispilopleura, but at least two other diploid sma ll barb' species (10 < cm). Data are collected from 1) the resource partiti oning of the piscivores in the field, 2) aquarium experiments on the predat or success in catching different prey species and size classes, 3) analyses on allometric growth and diet shifts in the field and 3) molecular genetic data, which will be combined to construct a hypothesis on the process of t he evolution of these piscivorous barbs. Being the major target of commerci al fisheries, knowledge on these piscivorous fish stocks and their prey spe cies is required for aiming at sustainable fisheries. preliminary data show a serious decline of fish stocks, most probably largely due to overexploit ing their spawning grounds.