Observations on reproduction of the Lake Tana barbs

Abstract

During the rainy season (September-November 1994), in tributaries of Lake Tana (Ethiopia), the Gumara, Gelda and Negashu, barbs of different morphotypes were ready to spawn, running and spent. The most numerous were barbs similar to Barbus intermedius common in many rivers of the Ethiopian Highlands. They were also found spawning in the Gumara and Gelda Rivers in the dry season (February 1996(February , 1997. There were no evident differences in time and place of spawning of barbs representing different morphotypes. Only zurki, bigmouth mini-eye and bighead were not found in the rivers. Spatial and temporal segregation may contribute to reproductive isolation of morphotypes spawning in rivers, but if reproductive isolation exists the main role must be played by differences in mating behaviour. Morphotypes of the Lake Tana barbs have different migration patterns. Barbs similar to the riverine B. intermedius may spend their lives in rivers or in the lake, moving to and fro. Barbs of acute, bigmouth big-eye and, perhaps, other morphotypes migrate downstream as alevins or fry, stay in the lake for several years and migrate back into rivers for spawning after reaching maturity. 1999 The Fisheries Society of the British Isles

Vulnerability to a small-scale commercial fishery of Lake Tana's (Ethiopia) endemic Labeobarbus compared with African catfish and Nile tilapia: An example of recruitment-overfishing?

“…Catchability is highly variable during the year: CPUE peaked sharply in July, September and especially August in both periods and more than 50% of the annual Labeobarbus yield is landed during the 3 months of peak spawning, July-September, in 1992, 1993and 2001 Fishermen cease their activities each year for 2 weeks to celebrate the Ethiopian new year ('Unkutatash') on 11 September followed by the 'Finding of the True Cross' (Meskel) on September 27, otherwise the landings of Labeobarbus could have even been higher. Highest CPUE is in the Gumara River mouth where the riverine spawning Labeobarbus species form large aggregations (de Graaf et al, 2005) before migrating 40 km upstream to spawn on the shallow, gravel beds (Nagelkerke and Sibbing, 1996;Dgebuadze et al, 1999;Palstra et al, 2004). The fishermen clearly target these spawning aggregations as is illustrated by the subsequent dominance and disappearance of riverine spawning/aggregating Labeobarbus species in the catch during these months (Fig.…”

Riverine spawning and reproductive segregation in a lacustrine cyprinid species flock, facilitated by homing?

“…Berrebi, 1995), including the diploid 'small barbs' of Lake Tana. Mina et al (1996a, b) and Dgebuadze et al (1999) have suggested a combination of maybe a few distinct species; however, they stressed the occurrence of a phenotypically plastic species using the original morphotypes as described by Nagelkerke et al (1994). Dgebuadze et al (1999) stated that there were no evident differences in time and place of spawning among barbs representing the different morphotypes, although sampling in the same area and period as Nagelkerke and Sibbing (1996).…”

“…Dgebuadze et al (1999) stated that there were no evident differences in time and place of spawning among barbs representing the different morphotypes, although sampling in the same area and period as Nagelkerke and Sibbing (1996). The few field data on spawning segregation among Lake Tana Labeobarbus Dgebuadze et al, 1999) were highly fragmentary, ambiguous, and lacking for many species, due to the difficult environment and logistics. In particular, heavy rainfalls and high water levels complicate access to remote areas and fish sampling ( fig.…”

“…Mina et al (1996a, b) and Dgebuadze et al (1999) have suggested a combination of maybe a few distinct species; however, they stressed the occurrence of a phenotypically plastic species using the original morphotypes as described by Nagelkerke et al (1994). Dgebuadze et al (1999) stated that there were no evident differences in time and place of spawning among barbs representing the different morphotypes, although sampling in the same area and period as Nagelkerke and Sibbing (1996). The few field data on spawning segregation among Lake Tana Labeobarbus Dgebuadze et al, 1999) were highly fragmentary, ambiguous, and lacking for many species, due to the difficult environment and logistics.…”

“…The evolutionary status of the diversified 'large Barbus' in Lake Tana, Ethiopia, is a controversial topic (Banister, 1973;Nagelkerke et al, 1994;Mina et al, 1996a, b;Nagelkerke and Sibbing, 1996;Sibbing et al, 1998;Berrebi and Valiushok, 1998;Dgebuadze et al, 1999). The latest revision (Nagelkerke and Sibbing, 2000) distinguished 15 biological species composing an endemic species flock of Barbus (subgenus Labeobarbus following Berrebi, 1995).…”