Estimated time change of dissolved oxygen and carbon dioxide concentrations in the interstitial water of red sea bream, Pagrus major, egg aggregation

Morphogenesis is most active during fish embryonic development with increased susceptibility to environmental stressors. In order to elucidate the causalities of malformations in fishes that produce buoyant eggs, this study estimated the time change of dissolved oxygen (DO) and carbon dioxide (DCD) concentrations in the interstitial water of red sea bream, Pagrus major, egg aggregation. Since direct measurement of DO and DCD concentrations is not possible by current methodologies, we measured those in one liter water containing approximately 500,000 eggs for their estimation. Calculated oxygen consumption and carbon dioxide excretion rates from observed data were 1.32 × 10− 6 and 2.16 × 10− 7 mg/ind/min, respectively. Volumetric method with these numeric values estimated that DO decreases below 10% saturation within 21 s and DCD increases to more than 135 mg/L within 60 min in the interstitial water of egg aggregation. These results suggest that hypoxia and hypercapnia may become teratogenic within a short time in the aquaculture practices of egg collection, treatment, and transportation where eggs aggregate at the water surface in containers or rearing tanks, or in the wild when eggs are exposed to red tide in the open sea.

► Hypoxia and hypercapnia during embryonic development cause malformations in fishes.
► These environmental stresses occur in the interstitial water of floating egg aggregation.
► Hypoxia below 10% oxygen saturation occurred within 21 seconds in such egg aggregation.
► Hypercapnia more than 135 mgCO2/L occurred within 60 minutes.
► Careful egg handling is necessary to prevent fish malformations in aquaculture.