Devastating effects of exotic Nile perch invasion in L.Victoria

Contributor based in Nairobi, Kenya

Nation Media Group

The introduction of the Nile perch into Lake Victoria has had devastating and long-lasting effects on the genetic diversity of its native cichlid species, according to a new study.

This artificial introduction has caused a significant ‘bottleneck effect,’ decimating many local fish population and altering the genomic structure of survivors, a group of scientists from Tanzania Fisheries Research Institute (Tafiri) and Tokyo Tech said.

The genomic analysis, which included 137 haplochromine species, showed that four species from the Mwanza Gulf, experienced a significant reduction in genetic diversity due to a ‘bottleneck event’.
“The timing of the bottleneck, which began during the 1970s–1980s and ended by the 1990s–2000s, corresponds to historical records of these endemic haplochromines’ disappearance and later resurgence,” explains Associate Professor Masato Nikaido from Tokyo Tech. This timing aligns with the introduction of the Nile perch for commercial purposes in the 1950s.
The study highlighted that the egg-eating cichlids Haplochromis sp. ‘matumbi hunter’ and Haplochromis microdon were particularly affected.
So severe was the bottleneck effect on the ‘matumbi hunter’ that its genome diverged significantly from closely related species. “This study presents, for the first time, the impacts of the Nile perch upsurge on the genetic structure of Lake Victoria haplochromines,” Peof Nikaido adds.