The Piscivorous Barbs of Lake Tana (Ethiopia): Major Questions On Their Evolution and Exploitation

Abstract

This paper surveys some major questions on the evolution of eight piscivorous Barbus species (B. acutirostris, B. dainellii, B. gorguari, B. longissimus, B. megastoma, B. platydorsus, B. truttiformis, and B. macrophtalmus), which together with six other species compose the endemic hexaploid 'large barb' species flock of Lake Tana. Preliminary data suggest that the major prey species of these piscivores (up to 90 cm length), in contrast to previous reports, is not Barbus trispilopleura, but at least two other diploid 'small barb' species (10 < cm). Data are collected from 1) the resource partitioning of the piscivores in the field, 2) aquarium experiments on the predator success in catching different prey species and size classes, 3) analyses on allometric growth and diet shifts in the field and 4) molecular genetic data, which will be combined to construct a hypothesis on the process of the evolution of these piscivorous barbs. Being the major target of commercial fisheries, knowledge on these piscivorous fish stocks and their prey species is required for aiming at sustainable fisheries. Preliminary data show a serious decline of fish stocks, most probably largely due to overexploiting their spawning grounds.