First record of giant freshwater prawn ___Macrobrachium rosenbergii___ (de Man, 1879) from small-scale fisheries in East Africa, confirmed with DNA barcoding

Abstract

We report, for the first time in the wild, giant freshwater prawn Macrobrachium rosenbergii populations in East Africa. Specimens caught by fishermen in the lower reaches of the Ruvu River and Rufiji Delta in coastal Tanzania were identified based on their morphology, with confirmation through DNA barcode analysis. The East African specimens clustered with the western M. rosenbergii dacqueti subspecies in a phylogenetic analysis based on new and published mitochondrial 16S rRNA and cytochrome C oxidase subunit I (COI) sequences. Captured specimens spanned a size range of 110–310 mm total length and > 35% of females carried external eggs, implying that populations were established and self-sustaining. No active culture facilities or ponds with M. rosenbergii were found within the catchment. Nevertheless, the invasive populations supported a small-scale fishery that used bottom-set seine nets. The demonstrated presence of M. rosenbergii in at least two river systems, combined with the existence of favourable brackish water habitats for completing their life cycle, may indicate that river systems in East Africa are at a high risk of invasion by this species. Key information gaps for the region are highlighted.