Studies On Embryonic Development And Oxygen Consumption Rate Of Early Life Stages Of Chinese Sturgeon, Acipenser Sinensis

The Chinese sturgeon, Acipenser sinensis (Gray), a typical anadromous fish, lives mainly in the continent shelf the East China and the Yellow Seas, and spawns in the Yangtze and the Pearl Rivers. Unfortunately, in the Yangtze River the spawning migration route was cut in 1981 by construction of the Gezhouba Dam and its spawning ground, which has been found since then, is now located in the reach of the river below the dam. Since 1983 commercial fishing of Chinese sturgeon has been prohibited and artificial propagation has been carried out, in order to protect its natural population. However, the population has greatly reduced. In 1988, the fish was put in the list as a state protected animal in class I. At present, great progress had been made in the fields of morphology, reproductive biology and, especially, reproductive ecology and stock assessment of the spawning population. Yet, knowledge of the development of embryos, especially the respiration of physiology remains rare. From 2003 to 2004,I studied the development of embryos and respiration physiology of early life stages of Chinese sturgeon. Conclusions from the studies are follows:1. The development of embryos was observed from fertilization to hatching out in 2003 and 2004. The development period was compartmentalized into 19 stages according to Т.А.дЕтлф and А.С.гинэвург(1954), Lu D C et al.(1986), Hochleithner et al.(1999) and Chen X H(2004a) and embryonic development schedule at 18.5±0.5℃ from ripeness egg to hatching was described. The hatching time at 18.5±0.5℃ was 120hrs (115hr-150hr) after fertilization.2. The effect of different water temperature on the embryonic development was studied. The low and upper temperature tolerance limits for the embryonic development were 14℃ and 26 ℃. The results showed that the temperature range for embryonic development of A. sinensis was obviously narrower than that of other fishes, such as Cyprinus carpio, Aristichthys nobilis, Leiocassis longirostris, that live in the same river.The optimum temperatures for the embryonic development were 18°C to 22 °C.3. The oxygen consumption rates of embryos (OCRs) were measured in closed volumetric flasks under different conditions (SOeggs^SSmL'1). The results showed that the OCRs ascended with increasing water temperature. The OCR was 0.69mg-1 OOeggs"1 -min'1 at 14°C, and 1.63mg-l OOeggs"1-min"1 at 26°C. The oxygen consumption of embryos increased with increasing development, When the pH was 6.4 and water temperature was 19°C, the OCR of embryo was 0.28mg-lOOeggs"1 min"1. The OCR of heart formation and beating stage was 0.87mgl00eggs~1-min'1; another fastigium period was at the stage of embryonic movement and hatching, the OCR was 1.54mg-100eggs"1-min"1.4. The influences of pH, salinity, phenol, NH/-N and alkalinity on the OCRs of embryos and larvae were measured in closed volumetric flasks. The OCR of embryos ascended when pH rising from 5.5 to 7.0, while decreased as pH rising from 7.0 to 9.0, suggesting that the optimal pH value for embryonic development was 6.5 to 7.5; OCR of embryos and larvae increased with salinity rising from 1.25%o to 2O%o, but became stable when salinity was higher than 40%o; both respiratory velocity and OCR increased in accord with elevated phenol concentration 6.25mgT1 to lOOmg-L"1, but decreased when phenol concentration over 200mg-L'1; OCR increased as the total NH4+-N level rising from 6.25mg-L"1 to lOOmg-L"1, beyond which it decreased; OCR of larvae ascended with alkalinity increasing.5. The OCR of larvae and juveniles of Chinese sturgeon were studied by Winkler's method. The results showed the water temperature affected OCR in larvae and juveniles. The OCR increased gradually with water temperature rising from 14°C to 26 °C. Changes of OCR were obvious at the ranges of low temperature (14°C to 16°C) and high temperature (22 °C to 26 °C), but amount of increase in OCR and metabolism were relatively lower under water temperature 16°C to 22 °C than of 14°C to 16°C and 22 "C to 26 °C. Daily fluctuation of the OCR was also observed in the experiment. The OCR was the highest at 13:00. The lowest OCR for larvae was at 3:00, and for juveniles, at 9:00. The OCR of fish was decreased with body weight increase, but the oxygen consumption amount was increased.6. The asphyxiation points of larvae and juveniles of Chinese sturgeon were studied for the first time. Asphyxiation point of the larvae (O.OeiO.Olg-ind."1) was 2.5754mg-L'1 and that of juvenile (0.09±0.01gind."1) was 2.608mg-L"1. The results showed the requirement of dissolve oxygen in the breed pond (>6mgL"1). The asphyxiation points both larvae and juveniles were high, indicating that higher D.O requirement for A.sinensis than D.Orequirement of other fishes, such as Acipenser schrenckii, Aristichthys nobilis, Ctenopharyngodon idellus.