Abstract:

Despite the species richness of the tilapiines, the fish have been compromised by various
factors like overfishing, climate change and un-controlled fish translocations. These
challenges particularly fish translocations have negatively impacted on native tilapiines
through competition, hybridization and introgression thus compromising genetic integrity of
the native tilapiines. Despite the prevailing research interventions, insufficient information is
available on the hybridization levels of different tilapiines in the Lake Victoria basin. The study
utilized nuclear microsatellite markers to investigate hybridization signals and compare the
genetic diversity of different tilapiines in Lake Victoria, Kenya, based on next-generation
sequencing. Tilapiines were collected from different beaches using experimental seine nets.
A fin clip/muscle tissue was extracted from the fish sample, preserved in 98% ethanol, for
subsequent genotyping in Meimberg laboratory at BOKU, Austria. The genetic structure based
generally revealed two clusters: one group of O. niloticus and the other congeneric species.
Despite this, some alleles of O. niloticus were observed in the genetic structure of other
congeneric tilapiines. This suggested some degree of admixture/introgression among the
studied tilapiines. With O. niloticus populations, there was a strong genetic differentiation
between Dunga, Usenge, Mbita, Siungu and Seka-Bay (FST = 0.06, 0.05, 0.09 and 0.06
respectively). The differences could be attributed to geographical isolation that has acted as
a barrier to gene flow between those populations. The apparent admixture of the different
populations might be attributed to uncontrolled fish translocations and escapees from fish
farms. Therefore, the current study contributes to identifying conservation measures of tilapiines that may be threatened and require management interventions.