NaCl盐度和NaHCO_3碱度对大鳞鲃幼鱼生长及鳃组织特征的影响

Effects of NaCl and NaHCO_3 on growth and gill microstructure in ju-venile Barbus capito

在水温22-25℃的条件下,研究不同盐度、碱度水体对大鳞鲃(Barbus capito)幼鱼生长、摄食和鳃组织的影响,探索了幼鱼生长的最适条件。单因素盐度梯度值设置为0(对照组)、2.0、4.0、6.1、7.8、10.0和11.9,实验结果表明,当盐度高于6.1时,大鳞鲃幼鱼的体长和体质量受到显著影响(P<0.05);盐度2.0时幼鱼的终末体质量值最大;盐度4.0时体质量特定增长率和饵料转化效率最高,盐度11.9时均降至最低;盐度到达7.8时对幼鱼生长有抑制作用,依据理论公式推算,幼鱼的最适生长盐度应为1.88。单因素碱度梯度值为10.00、15.83、25.10、39.80和63.12 mmol/L,碱度高于25.10 mmol/L时对幼鱼的体质量、饵料转化效率及总摄食量均有显著影响(P<0.05);碱度15.83 mmol/L时幼鱼的终末体质量、体质量生长率和饵料转化效率值最高,碱度63.12 mmol/L时最低。碱度到达39.80 mmol/L时对幼鱼生长有抑制作用,依据理论公式推算,幼鱼的最适生长碱度为20.57 mmol/L。从鳃组织的显微结构观察结果来看,随着盐度和碱度的升高,鳃小片上皮细胞出现肿胀、脱落和坏死的现象,泌氯细胞的体积膨胀,从而影响了幼鱼的生长。综上所述,大鳞鲃幼鱼期,养殖盐度不宜超过6.1,碱度不超过25.10 mmol/L。

We evaluated the effects of salinity and alkalinity on growth, feeding, and gill microstructure in juvenile Barbus capito. The fish were reared at salinity of 0 （control group）, 2.0, 4.0, 6.1, 7.8, 10.0, or 11.9 for 60 d with temperature of 22-25 ℃. The body length, body weight, and specific growth rate （SGR） of juveniles were signifi- cantly lower in fish held at salinities 〈6.1 than in those held in salinity 〉6.1（P〈0.05）. The maximum final body weight was highest in the fish reared at 2.0. The specific growth rate of weight （SGRW） and feed conversion effi- ciency （FCE） were highest in fish held at 4.0 and lowest in fish held at 11.9. Our results suggest the optimal salin- ity for growth is 1.88, whereas exposure to levels ≥7.8 results in negative effects. Fish were also reared at 10.00, 15.83, 25.10, 39.80, and 63.12 mmol/L NaHCO3. The body weight, length, and the SGR of juveniles reared in water with 〈25.10 mmol/L NaHCO3were significantly lower than in the remaining groups （P〈0.05）. The largest final body weight, body length, SGR, SGRW, and FCE were in fish reared at 15.83 mmol/L NaHCO3.The fish reared at 63.12 mmol/L NaHCO3 had the lowest values for all indices. Rearing in water with NaHCO3 levels 〉39.80 mmol/L had negative effects and the optimal alkalinity for growth was 20.57 mmol/L. Observation of gill microstructure revealed hypertrophy in the chloride cells, and both hypertrophy and edema in the epithelial cells as salinity and alkalinity levels increased, thereby affecting the growth of the fish. In conclusion, the salinity should bebelow 6.1 or the alkalinity should be below 25.10 mmol/L in the Barbus capito larvae culture.