投喂不同密度卤虫无节幼体对灰海马幼体生长和存活的影响

为比较投喂不同密度卤虫对灰海马幼体生长和存活的影响,共设3个卤虫无节幼体密度组5(A)、10(B)和20(C)个/mL],用初始密度为2尾/L的灰海马幼体进行为期50 d的养殖研究.结果显示,总体而言,3个饵料密度对灰海马幼体的存活、生长有显著影响(P<0.05).在前10 d,3组海马间的成活率和生长速度差异均不显著(P>0.05);d20～50,B、C两组海马的成活率均显著高于A组(P<0.05),而B、C两组之间无显著差异(P>0.05).d 20时,B、C两组的生长速度显著快于A组(P<0.05);d 30往后,A、C两组的生长速度开始加快,随后3组海马生长速度间的差距进一步缩小,直至A组的体质量和体高超过B组和C组(P<0.05),而B、C两组间的差异显著性消失(P>0.05).随着投放卤虫密度的增加,各时间点水体的pH和溶氧含量呈显著下降的趋势(P<0.05);C组氨态氮含量显著高于A组和B组(P<0.05);除第24 h外,3组间亚硝态氮的含量差异不显著.综合结果表明,卤虫的最适投喂密度应随着灰海马的生长进行适时调整.从初孵至d 10,饵料密度以10个/mL最佳;从d 10起,将饵料密度上调至20个/mL;d 30后当海马密度降至0.5～1尾/L时,卤虫密度可降至10个/mL左右.图2表1参21

Growth and Survival of Juvenile Lined Seahorse (Hippocampus erectus) at Different Food Densities

To investigate the effect of Artemia nauplii with different densities on the survival and growth of Hippocampus erectus juveniles,newly hatched H.erectus juveniles were fed with Artemia nauplii for 50 days,which were divided into three groups 5 nauplii/mL(A),10 nauplii/mL(B) and 20 nauplii/mL(C)].The results show that the survival and growth of juveniles could not be explained by three food densities during the first 10 days.The survival of juveniles with 10 nauplii/mL and 20 nauplii/mL food densities were significantly higher than that with 5 nauplii/mL from day 20 to day 50(P<0.05),but there was no significant difference found between the survival in treatments B and C.Additionally,the weight and height of juveniles in treatments B and C were significantly higher than that in treatment A on day 20(P<0.05).The weight and height of juveniles in treatments A and C increased dramatically than that in treatment B from day 30(P<0.05),and the difference in growth among the three food densities groups reduced on day 40,then the weight and height of juveniles in treatment A was higher than those in treatments B and C(P<0.05).The weight gain(WG),condition factor(CF) and special growth rates(SGR) of the juveniles with three food densities were not significantly different on day 50.The pH and DO of water decreased with increasing of food density over 24 h,however,water quality was not deteriorated to become a major factor reducing the growth of the juveniles.Furthermore,the concentration of ammonia-N in treatment C was significantly higher than that in treatments