Physiological effects of hypoxia on Atlantic croaker

Atlantic croaker is an early maturing, benthic fish, which regularly encounters low dissolved oxygen conditions during its peak growing months in late spring to early fall in the Chesapeake Bay. Under hypoxic conditions fishes often show reduced maximum metabolic rates that, in turn, can reduce gonadal and somatic growth, and suppress immune function. We have conducted a series of studies on the physiological effects of hypoxia on croaker. We used stopped flow respirometry to measure critical oxygen level, the oxygen level below which aerobic metabolism cannot be maintained. Mean critical oxygen level for croaker (n = 11) was 29.11± 2.47% saturation (3.95 ± 0.47 mg O2 l-1, 46.29± 3.93 mm Hg; 27oC). Future experiments will measure glucose levels, hematocrit, GnRH mRNA, and gonadal index of croaker exposed to hypoxia for acute and chronic periods of time.