The migration of aquatic macrocrustaceans over an artificial barrier in the uThukela river, South Africa

Diadromous macrocrustaceans need connectivity between the ocean, estuary and river to complete their life cycle. Instream barriers in lower reaches of rivers threaten upstream migrations of diadromous macrocrustaceans. Varuna litterata migrate upstream after a spawning event out at sea. These migration events have been poorly documented. We documented the presence V. litterata and Macrobrachium spp. at a vertical slot fishway and a rock ramp on the Lower Thukela River Bulk Water Supply Scheme Weir, KwaZulu-Natal, South Africa, during 2021–2022. We found Macrobrachium spp. and V. litterata made use of the rock ramp. However, the vertical slot fishway did hinder the migration of V. litterata significantly, as found in other studies.