Effect of water level and water quality on small‐sized and juvenile fish assemblages in the littoral zones of the Zambezi/Chobe floodplain

• Published in: African journal of ecology 2021-06, Vol.59 (2), p.436-448
• Main Authors: Simasiku, Evans Kamwi, Hay, Clinton, Abah, James
• Format: Article
• Language: English
• Subjects: catch per unit effort; Cichlids; Composition; Coptodon rendalli; Dissolved oxygen; Fish; Fish migration; Fish populations; Flooding; Floodplains; juvenile fishes; Juveniles; Littoral environments; Littoral zone; Natural flow; Oreochromis andersonii; Peak floods; pH effects; Phases; Populations; Recession; seine net; Species composition; Water levels; Water quality; Water temperature; Zambezi/Chobe floodplain
• ISSN: 0141-6707; 1365-2028
• DOI: 10.1111/aje.12846

The effect of flooding phase and water quality on the littoral fish species of the Zambezi/Chobe floodplain was assessed between March 2017 and February 2018. Using the similarity percentage analyses (SIMPER), a 61.9% dissimilarity was detected in fish assemblages among the four flooding phases of the Zambezi/Chobe floodplain (rising, peak, recession and low flooding phase). Cichlids (63.1%) were the most dominant taxa during the peak flooding phase while cyprinids were dominant during the rising (40.7%), recession (45.3%) and low flooding phases (40.9%), respectively. Juveniles of the two commercially important species, Oreochromis andersonii and Coptodon rendalli, were among the four abundant species across the four flooding phases of the Zambezi/Chobe floodplain. Higher densities of these two species were in synchrony with the peak flooding phase, characterised by high levels of dissolved oxygen (5.7 ± 1.0 mg/L), neutral pH (7.9) and moderate water temperature (27.6 ± 1.1°C). During the flood recession phase, a severe decline in juvenile of the commercially important species (O. andersonii and C. rendalli) coincided with fish migration off the littoral zone into the main river at a mean size between 70 and 80 mm SL. Generally, the observed variations in the fish species composition during the different stages of flooding might reflect the influence of water quality and water volume to sustain large fish assemblages on the littoral zone of the Zambezi/Chobe floodplain. Any change in the natural flow and reduction in water volume of the Zambezi/Chobe floodplain might negatively affect the recruitment of juvenile fish into adult populations. Résumé L'effet de la phase de crue et de la qualité de l'eau sur les espèces de poissons du littoral de la plaine inondable du Zambèze et de la Chobe a été évalué entre mars 2017 et février 2018. À l’aide d’analyses de taux de similarité (SIMPER), nous avons détecté une dissemblance de 61.9% au sein des peuplements de poissons au cours des quatre phases de crue de la plaine inondable du Zambèze et de la Chobe (phase de montée, maximale, de récession et de faible crue). Les cichlidés (63.1%) étaient les taxons les plus dominants pendant la phase d’inondation maximale, tandis que les cyprinidés dominaient respectivement pendant les phases de montée (40.7%), de récession (45.3%) et de faible crue (40.9%). Alevins des deux espèces d’intérêt commercial: Les espèces Oreochromis andersonii et Coptodon rendalli faisaient parti