BASIC STUDIES FOR TECHNICAL DEVELOPMENTS ON SEED PRODUCTION IN AQUACULTURE

本研究的主要目的是了解作为水产养殖种子的水产养殖幼鱼早期死亡的原因和机制的基本信息。我们从病原学、诊断学、免疫学、生理学、营养学和环境学等方面进行了调查，得到以下结果：1)。在种子生产过程中，由于传染病造成大量死亡。其中，斑马鱼的SJNNV和黄尾鱼的YAV等病毒病是目前存在的严重问题。很明显，sJnnv（斑纹杰克幼虫的病毒性神经坏死）的可能途径是它们的亲代产卵。鱼苗在吸收卵黄后或吸收卵黄期间遇到食物颗粒，生长正常。如果长时间得不到适当的食物，幼虫可能达到不可逆的营养不良状态，最终死亡。进入这一终末阶段的幼虫被称为……更多的已经达到了PNR（不返回点）。在实际应用中，PNR可定义为第一次取食的最大延迟时间，但仍能使50%的幼虫存活。介绍了各种鱼类中饥饿引起的死亡和PNR的一些例子。成功地开发了臭氧作为水产养殖系统消毒剂的应用。所有鱼类病原体的细菌计数在每升总残余氧化剂（TRO）超过0.04-0.06毫克时下降。该结果表明，以大于1.0 mg /1的TRO处理几分钟，可以有效地对海水进行消毒。为了增强种子的遗传特性，对鳟鱼卵进行了转基因试验，证实了在卵期引入的外源基因在后代中具有活性。同时，进行了倍性操作，得到以下结果：每个细胞最大核仁数的变化与它们的年龄有关。雌性虹鳟鱼与另一种鲑科鱼类杂交，产生了12个组合的二倍体和三倍体杂交种。此外，还获得了3种medaka的杂交雌性（三基因组异体三倍体）。少

The main purposes of this study are to obtain basic informations about the causes and mechanism of early death during larval and young fish used aquaculture as the seed for aquaculture. We have investigated from pathogenic, diagnostic,immunological, physiological, nutritional and environmental points of view and obtained the following results.1). There are mass mortalities during seed production due to infectious diseases. Among these problems, the viral diseases such as SJNNV in the striped jack and YAV in the yellowtail are serious problem at present. It has become clear that possible courses of the sJnnv( viral nervous necrosis in larval striped jack) are their parental spawners.2). fish larvae encountering food particles some time after or during the period of yolk absorption grow normally. If suitable food is not available for longer periods, the larvae may attained state of irreversible inanition, at the end of which mortality occurs. Larvae entering this terminal phase are said … More to have reached the PNR( point-of-no-return). For practical purposes, PNR may be defined as the maximum delay in first feeding that still enables 50 % of the larvae to survive. Some examples of starvation-induced mortality and PNR in various fish species are presented.3). Successful use of ozone as a disinfectant for aquaculture system was developed. Bacterial counts of all fish pathogens decreased at more than 0.04-0.06 mg of total residual oxidans(TRO) per liter. This result indicates that ozone treatment at more than 1.0 mg of TRO/1 for several minutes is able to disinfect seawater for mariculture efficiently.4).In order to augment the genetic properties of the seed, transgenenic method has been tried on trout eggs and confirmed that foreign genes introduced during egg stage become active in the offsprings. At the same time,ploidy manipulations have been done and got the following results; the variation in the maximum number of nucleoli per cell is related to their age. Diploid and triploid hybrids with 12 combinations have been produced by the crosses between female rainbow trout and another salmonids fishes. In addition, hybrids females among 3 species of medaka have been produced( trigenomic allotriploids). Less