Foraging Costs of Hypoxia Acclimation in the Swamp-Dwelling African Cyprinid, Barbus neumayeri

Abstract

This study described the behavior of the swamp-dwelling African cyprinid Barbus neumayeri in response to laboratory acclimation to normoxic and hypoxic conditions to detect costs associated with hypoxia exposure. Behavioral observations were conducted every two weeks over a four-week acclimation period in both normoxic and hypoxic conditions, and feeding trials were conducted after six weeks of acclimation. Gill ventilations were shallower in normoxia-acclimated fish than in hypoxia-acclimated individuals, and gill ventilation rate declined over the hypoxia acclimation. There was no effect of hypoxia acclimation on routine activity; however, individuals acclimated to hypoxia showed a depression in feeding rate relative to normoxia acclimation. This decline in feeding activity under hypoxia acclimation may account, at least in part, for the lower condition of the hypoxia-acclimated fish. These findings suggest that hypoxia exposure does not significantly impact routine activity levels of these swamp-adapted fishes, but seems to depress higher energy activities such as feeding rate.