Detection of Unauthorized Tilapia Species Circulating in Cage Farms on Lake Volta

Abstract

ABSTRACT The Akosombo strain of Nile tilapia is the only approved tilapia strain for culture in Ghana. In this study, exotic red tilapia suspected to be cultured in fish farms within the Lower Volta River Basin of the Lake Volta were collected for species identification based on their morphological features. A molecular screening using DNA barcoding sequencing was then performed on the samples targeting the cytochrome C oxidase subunit 1 mitochondrial gene ( COI ). Morphological characterization identified three taxa, predominantly red tilapia ( Oreochromis sp.), alongside Coptodon sp. and a single O. niloticus specimen. Phylogenetic analysis resolved two well‐supported clusters; one corresponding to native Ghanaian O. niloticus haplotypes and another comprising red tilapia lineages not naturally occurring in West African waters. The widespread occurrence of red tilapia, an introduced, hybridized domesticated strain not approved for aquaculture production in Ghana, strongly suggests intentional or accidental introduction of foreign broodstock. Their presence raises concerns regarding genetic introgression into native O. niloticus populations, including the locally important and approved Akosombo strain, as well as increased vulnerability to transboundary fish diseases. These findings highlight a significant breach in national biosecurity and stock management systems. Strengthened genetic monitoring, farmer education, hatchery regulation, import control enforcement, and structured breeding programs are urgently required to safeguard Ghana's aquaculture industry and conserve indigenous tilapia genetic resources.