Hypoxic Threshold for Yellow Perch Embryonic Development

Abstract

AbstractThe effects of hypoxia on the embryonic development and larval survival of Yellow Perch were examined at three different dissolved oxygen (DO) concentrations: hypoxia (H) 3–4 mg/L, moderate‐hypoxia (MH) 5 mg/L, and normoxia (N) 7–8 mg/L. Each DO concentration was tested in replicates of four within twelve 38‐L aquaria, at temperatures of 16.8 ± 0.4°C. To examine the effects of DO on the incubation of Yellow Perch embryos, samples of fertilized eggs (1.58 ± 0.1 g, 631 eggs/g) were placed in twelve 38‐L aquaria. The embryos were observed until hatching, or mortality. Significant differences were observed in embryonic survival and hatching among the three DO treatments. At 43 h after fertilization (haf, optic‐cup stage), embryonic development in H‐treatment groups was completely arrested, while the embryos of MH and N groups developed normally, possessing a distinct body trunk shape and optic caps at 43 haf. At 168 haf, all embryos were either developmentally arrested or dead in H treatment groups, while average percentage of live embryos in MH and N treatment groups was 12 ± 9.8% and 99 ± 0.4%, respectively. Heartbeat appeared at 72 haf in the N treatment groups, and about 96 haf in MH treatment groups. Heartbeat rate differed significantly (P < 0.05) between the N and MH groups (143 ± 10/min and 117 ± 17/min, respectively). Hatching rate in N groups (78.3 ± 8.6%) was significantly higher than that of MH groups (20.0 ± 8.7%), and there was no hatching observed in H groups. In the second experiment, 300 freshly hatched (72haf) larvae were stocked to each of the 12 aquaria to observe the effect of different oxygen concentrations (H, MH, and N) on survival for 5 d. We did not observe an effect on survival of the larvae. Overall, results indicate that hypoxic conditions below 3.5 mg/L (39% saturation at 16°C) have a profound negative effect on the development and survival of Yellow Perch embryos, while Yellow Perch larvae are capable of surviving this low‐DO environment.