Caridina nilotica (Roux, 1833) holds considerable potential for supporting local aquaculture in Lake Victoria, particularly in fish feed formulations. Accurate biomass estimation is essential for sustainable exploitation, yet current harvesting strategies are hindered by uncertainties in abundance and ecological sustainability. Traditional hydroacoustic surveys have relied on inappropriate target strength (TS) models based on morphologically dissimilar Antarctic shrimp, leading to unreliable biomass estimates. This study presents a species-specific TS model for C. nilotica (Caridina), developed using the Distorted Wave Born Approximation (DWBA) as implemented in ZooScatR. Geometric and morphometric parameters were derived by digitizing images of fresh Caridina specimens, generating a consensus shape catalogue. These inputs, combined with species-specific and environmental material properties, were used to simulate TS values at 70 and 120 kHz—frequencies routinely employed in Lake Victoria acoustic surveys. Predicted TS values at 120 kHz for Caridina ranging from 2 to 25 mm varied between –127.87 and –71.91 dB re-1 m², with a mean length-weighted TS of –87.99 dB re-1m2. Backscattering intensity was isolated using dB differencing (5–10 dB range), and biomass was calculated using a derived TS per kilogram of –37.76 dB re-1m2 kg⁻¹ (95% CI: –40.12, –35.17). Lake-wide biomass estimates showed an increasing trend, from 957,467 metric tonnes (95% CI: 853,094–1,066,303 MT) in 2007 to 1,596,668 metric tonnes (95% CI: 1,467,788–1,725,245 MT) in 2022. These results are consistent with depth-stratified patterns observed in fish landing data. The revised estimates are consistently higher than those obtained using previous methods and better reflect ecological expectations, including support for higher predator abundance, greater lake productivity, and the feasibility of commercial Caridina exploitation. The development of a robust TS model marks a key advancement in hydroacoustic biomass estimation, enhancing our understanding of Lake Victoria’s food web and supporting data-driven fisheries and aquaculture management.
Keywords: Caridina nilotica, hydroacoustics, target strength (TS), Lake Victoria, DWBA, biomass estimation, aquaculture, fisheries management, ecosystem monitoring