盐度对赤点石斑鱼受精卵发育的影响及仔鱼活力的判断

Effects of salinity on hatching rates and survival activity index of the larvae of Epinephelus akaara

观察比较了10个盐度梯度(44.0、41.0、38.0、35.0、自然海水盐度30.5～32.5、27.0、24.0、21.0、18.0、15.0)下赤点石斑鱼受精卵的孵化率和畸形率。对12批初孵仔鱼进行耐饥饿试验,并测定其不投饵存活系数SAI值。结果表明,赤点石斑鱼受精卵孵化的适宜盐度为38.0～24.0,最适盐度为35.0～27.0。盐度高于35.0,孵化率随盐度的升高而降低,仔鱼畸形率则随之升高。盐度低于24.0,孵化率随盐度的降低而降低,仔鱼畸形率则随之升高。从盐度38.0到41.0以及24.0到21.0是2个对受精卵孵化率和仔鱼畸形率影响很大的盐度梯度。高于或低于这2个盐度梯度,孵化率即明显大幅度降低,畸形率则大幅度升高。赤点石斑鱼仔鱼的SAI值为3.19～12.42,低于长吻鯵和黄条鰤的SAI值。仔鱼的SAI值与卵的受精率、孵化率呈正相关关系。只有SAI值大于5的仔鱼才有可能被进一步培育成苗,低于5的将在数天内死亡。

The effects of seawater salinity on hatching rate and survival activity index (SAI) of Epinephelus akaara were studied in the laboratory. 10 different levels of salinity were set as follows: 44.0, 41.0, 38.0,35. 0,natural seawater salinity about 30.5-32.5, 27.0, 24.0, 21.0, 18.0, 15.0. Five broods of fertilized eggs were used for observation. 12 broods of newly hatched larvae were used to carry out starvation tests and evaluate their SAI (survival activity index)volume. 100 newly hatched larvae were reared in 500mL beaker without food and aeration at natural room temperature (about 26 - 27°). The results showed that: 1. Salinity from 38.0 to 24.0 is suitable for hatching and the optimum is from 35.0 to 27.0. When salinity higher than 35.0, the higher the salinity, the lower the hatching rates and the higher abnormal rates. When salinity lower than 27.0, the lower the salinity, the lower the hatching rates and the higher abnormal rates. Salinities from 41.0 to 38.0 and from 24.0 to 21.0 may be two critical ranges causing notable differences in the hatching rate of fertilized eggs and abnormal rate of the newly hatching larvae. 2.The SAI values of the fish were 3 .196 ~ 12.42, lower than other fishes such as Pseudocaranx dentex and Seriola aureovittara and showed positive relationship to the fertilization rates and hatching rates. Only the larvae which SAI volumes were higher than 5 could be reared to reach the stage when juveniles finish their metamorphosis and become young fish. Others would die in several days.