Odonate larval density and Chironomidae availability predict the survival of Nile tilapia post-larvae

Abstract

Odonata larvae can compromise the survival of Nile tilapia (Oreochromis niloticus) post-larvae, causing losses during early rearing. This study assessed the effects of predator density and genus and the provision of Chironomidae on post-larval survival. Data were obtained from six experimental phases conducted between November 2019 and March 2020 in Alfenas, Minas Gerais, Brazil. The dataset comprised 118 experimental units, of which 73 from the density trials were included in the main models. Survival was analyzed using a binomial model, predation using a negative binomial model, and the reduction in predation using bootstrap analysis with 2,000 resamples. Increasing predator density increased predation (χ² = 50.90; p < 0.001) and reduced survival (χ² = 269.94; p < 0.001), with greater predation pressure exerted by Miathyria than by Erythemis. The provision of Chironomidae was associated with descriptive reductions in predation of 53.4–62.4% for Miathyria and up to 50.0% for Erythemis. The mean reduction was 6.31 post-larvae per aquarium (95% BCa CI: 2.15–10.29). The random forest model achieved an accuracy of 90.5% and an AUC of 0.963. The results indicate that predation risk depends primarily on predator density and genus and that Chironomidae may serve as alternative prey, although its use in production ponds requires validation under production conditions and assessment of sanitary risks.