【作者】 李艳华；

【导师】 危起伟；

【作者基本信息】 华中农业大学 ， 湿地资源与环境， 2013， 博士

【摘要】 鳇是世界现存两种鳇属鱼类之一,主要分布于黑龙江及其支流(包括乌苏里江、松花江,俄罗斯的结雅河、布列亚河、石勒喀河、喀尔古纳河、鄂毕河、音果达河)、兴凯湖和奥列列湖。鳇存在着淡水定居型与河口半洄游型两种生活史,前者完全定居在黑龙江下游、中游以及支流的淡水中,后者在河流干道产卵并且洄游至河口摄食生长。最近几年的捕捞调查表明,鳇捕捞产量几乎集中于下游与河口,中游的产量已近枯竭,我国的捕捞江段主要在抚远江段,年产量已不足10t。2010年,鳇被IUCN红色目录列为极危等级物种(CR)。到目前为止,黑龙江干流尚未建坝,导致鳇资源枯竭以致极危的主要原因是受鱼子酱价格刺激带来的合法与非法的过度捕捞,水域污染以及河道中食物的匮乏。鉴于鳇的濒危状态,中国政府自2002年开始对其进行大规模人工增殖放流,到2008年止,黑龙江中游下段的抚远县已经放流1千万尾仔稚鱼。养殖的仔稚鱼也在黑龙江中游沿岸的一些城市进行了放流,如黑河、萝北、同江。在这些地方放流的鳇全长大多在7-10cm。尽管如此,目前依然没有一整套关于鳇放流的规范,放流鱼的来源、放流地点、放流鱼的尺寸大小以及放流规模依然带有很强的随意性与不确定性。为了查清放流鱼的来源、所处发育阶段以及洄游特性,以及更好的指导今后的人工放流,本文就鳇繁殖场附近的生境、鳇的胚后发育形态以及个体发育行为和环境因子对洄游的影响进行了系列研究。具体采用的方法和获得的结果如下：1.根据原位观测得知鳇抚远江段产卵场附近流态平缓,坡岸底质主要以沙和砂砾构成,有少量鹅卵石,推知河床质主要以砾石和鹅卵石组成。河较宽,两岸沙洲发育较多,河中心亦有沙洲发育,两岸覆盖物以河柳居多。经过3处原位观察测量算得产卵场河道主流附近表层水的流速值在0.15-0.46m·s-1之间,平均流速0.31m·s-1,产卵场在产卵季节最大水深可达14m。水下光照强度在水表层以下1m处衰减开始极显著,在水深3-14m,水下照度几乎稳定在0.51x左右。透明度一般在0.3-0.4m之间。2.样本系黑龙江野外采集的鳇(Huso dauricus)亲体经人工受精后孵出的子一代,对刚出膜的仔鱼[0日龄,(12.08±0.68) mm]到早期稚鱼[60日龄,(129.21±7.69)mm]的胚后发育形态进行了观察。形态发育上看来,鳇仔鱼的胚后发育可分为2个时期：早期仔鱼,即从刚出膜(0日龄)到初次开口摄食(9日龄)；晚期仔鱼,即从初次开口摄食到各器官发育基本完成,体透明特征消失,鳍褶和颌齿彻底消失(49日龄),以后进入早期稚鱼[50日龄,(106.78±9.87)mm]。早期仔鱼的形态发育和分化明显较晚期仔鱼和稚鱼阶段快,运动、呼吸、感觉和消化等器官在此期发育与分化同步协调,且速度快,使得仔鱼快速获得避敌与摄食能力,提高了成活率。晚期仔鱼主要表现为各骨板的分化和完善,鱼鳍游泳器官功能的进一步强化,鳔的发生和发育,表明此期游泳和躲避敌害能力处于进一步增强中。3.作者对来自黑龙江中游的鳇早期生活史进行了实验室研究,来定量化其个体发育行为和比较在相似试验条件下的鳇早期生活史行为。孵出的自由胚启动高强度的顺流洄游,洄游在1日龄达到峰值,继续高强度洄游直至3日龄,然后洄游强度在4-6日龄逐渐减弱,在第7日龄停止洄游(持续8天的洄游)。洄游的鳇喜好明亮(明亮区和白色底质)和开阔栖息地,并且高高地游泳于水面(每日离底高度众值在3.5m)。21-22日龄仔鱼启动第二波洄游,在34-36日龄有一个洄游峰值(每尾鱼每5min洄游4次)。稚鱼继续低强度的洄游(每尾鱼每5min洄游1次),直至66日龄,暗示着早期生活史进行着长周期的洄游。当绝大多数自由胚在第9日龄发育成仔鱼,早期仔鱼是非洄游的(像晚期的自由胚一样),喜欢明亮和开阔的栖息地,游泳高高地游离底面直至35日龄。所有生活史[自由胚、仔鱼以及早期稚鱼(至观察结束的第66日龄)]喜欢白色底质,暗示着野生鳇强烈的对白色栖息地的适应需求。晚期仔鱼和稚鱼逐渐丧失对明亮区的喜好,并且游泳日渐接近底面,暗示着向底栖生活转化。自由胚、仔鱼和早期稚鱼强烈喜好开阔的底质,暗示着这三个生活史的野生鲟鱼也喜好开阔的底质。自由胚和仔鱼天生的洄游特征与以前在相似的试验条件下观察到的鳇的行为特征大体上相似,但是在具体的洄游特征上存在差异。这些结果显示在这同一河段存在着两个拥有不同早期行为的种群。因此,在养殖鳇用于增殖放流时,可能需要高度注意,防止两个种群在放流时混淆,导致产生不适应野外环境的早期生活史的鳇。4.就四种环境因素(水流、底质、饲养水环境条件、昼夜节律)对早期生活史的鳇(0-8日龄自由胚、9-49日龄仔鱼、50-66日龄稚鱼)洄游的影响进行了研究。试验在六个结合了各种环境因子的人工循环溪流里进行。水流速度对自由胚的洄游强度有着正相关的影响,此外,高流速还延迟了晚期自由胚停止洄游的时间。但是,在不同流速条件下的洄游的自由胚和仔鱼依然有着洄游相似距离的本能。结果还显示在启动洄游或者停止洄游时存在着一个激发流速。底质类型对早期自由胚的洄游没有影响,但是随着仔鱼日龄的不同对仔鱼的洄游有着不同的影响。与一直饲养在高流速溪流桶内同样日龄的鱼相比,饲养在静水环境下的中期仔鱼至稚鱼,当放置在高流速溪流桶内时洄游将加快,显示出补偿洄游。这种补偿洄游并未在饲养在低流速(7.2cm-s-1)桶的鱼中出现,这表明补偿洄游的出现需要一个7.2至31.7cm.s-1的激发流速存在。流速对自由胚和稚鱼的昼夜洄游节律没有影响,但是较快的流速可能通过延迟鱼类的生长发育而间接地推迟昼夜洄游节律差异的出现。对于鳇的人工增殖放流而言,研究表明在养殖过程中必须分开饲养不同种群的鳇以免混淆,补偿洄游的出现表明放流的鱼从小饲养的水流环境并未影响其洄游本能,静水饲养的鱼照样适合于放流,只不过放流的鱼以处于洄游期的仔鱼为好,而不是非洄游或者低强度洄游的稚鱼,这样有利于最大化分散放流的鱼而减少放流鱼对食物的竞争。并且仔鱼以放流在一个底部流速超过30cms-1,含有沙与小卵石的底质江段较好。5.对于放流的地点与鳇苗种规格而言,我们认为要充分利用两个种群的鳇的不同特点有针对性地进行放流。如果是非洄游性的仔鱼,我们可以将放流大的地点安排在抚远以上的勤得利、肇兴和萝北,甚至嘉荫和逊克,具体地点则安排在这些大地点的沙滩、沙洲上分散进行,减少摄食竞争的同时增殖中游的渔业资源。如果是洄游性的仔鱼,放流地点可就近在抚远县放流,具体地点可以就近选择在产卵场附近河流底部流速大于0.30m·s-1的河段进行。根据我们研究的结果,洄游性仔鱼会加速往下洄游,越早放流就越有可能使放流仔鱼加入到野生仔鱼的队伍中。但是很多时候,我们无法区分要放流的仔鱼究竟是洄游性的还是非洄游性的,这时为保险起见,我们还是建议将放流地点选择在抚远县附近河流底部流速大于30cm.s-1的河段进行,这样有利于洄游性的仔鱼在洄游过程中找到合适的摄食场。综合考虑敌害因素,养殖成本与洄游因素,我们建议选择5-8cm(23-36日龄)的仔鱼进行放流,因为此时的仔鱼已经有较发达的骨板,这样可以大大增强对敌害摄食的抵御。并且此期的仔鱼如果是洄游性的种群还依然具备洄游特征。但放流5-8cm的仔鱼,其成活率究竟如何,尚需人工标志放流进行效果评价。更多还原

【Abstract】 Huso dauricus is one of the existing two Huso in the world, it mainly distributed in Amur river and its tributaries (including Ussuri, Sungari, Zeya river, Bureya river, Shilka river, Argun river, Ob river, and Ingoda river), Khanka lake and Orel lake. There are two kinds of life history H. dauricus, they are fresh water type and estuary half migration type. Fresh water type completely settle in freshwater of lower and middle reach of Amur river and tributaries, estuary half migration type breed in rivers artery and migrate to the estuary for forage. In recent years, fishing survey show that H. dauricus fishing production almost focused on the lower reach and estuary of the river, fishing production in middle reach has nearly exhausted, China’s fishing mainly limited in the Fuyuan reach, and the annual output has been less than10t. In2010, H. dauricus was listed as critically endangered species by IUCN red list (CR). So far, Amur river main stream has not been built dam, the main reason that lead H. dauricus resources to exhaustion is the legal and illegal overfishing stimulated by the caviar prices, water pollution and lack of food in river channel.Due to its endangered status, the Chinese government has conducted large-scale population enhancement since2002, releasing over10million larvae and juveniles in Fuyuan county (lower-middle reach of the Amur River) from2002to2008. Cultured fish were also stocked at other places along the middle reach of the Amur River such as Heihe, Luobei and Tongjiang. The H. dauricus released in these places were7-10cm TL (Total Length). However, a set of standard on H. dauricus resource enhancement and releasing is still unavailable at present. The source of released fish, releasing location, the size of released fish and releasing scale are still haphazard and uncertain. In order to find out the source of the releasing fish, the developmental stage and its migration characteristics, and better guide future resource enhancement and releasing, this paper conducted a series of research on the habitat of H. dauricus spawning site, the morphological feature of H. dauricus on postembryonic developing, ontogenetic behavior and the effects of environmental factors on migration. The specific methods and the results obtained were as follows:1. According to the observation in situ, we know that the river reach near H. dauricus spawning ground has a low flow, and substrates on banks is mainly composed of sand and gravel, there are a few pebbles on banks, so, we can infer that river bed substrates is mainly composed of gravel and pebbles. The river is wide, and both side banks have lots of sandy shoal, the center of river also have sandy shoal, the mulch in river banks is mainly composed of river willow. By three places observations in situ, we measured the surface water flow near spawning ground ranged from0.15m·s-1to0.46m·s-1, and averaged0.31m·s-1. We also measured the maximal water depth near spawning ground was14m, the underwater illumination1m below the water surface decayed very much, in the depth of3-14m, underwater illumination almost stable in0.51x or so. Transparency is almost stable at0.3-0.4m.2. The morphological observation during postembryonic development of first filial generation of H. dauricus were studied under rearing conditions, whose parents were captured from the Amur river. New born prelarval [0-day age,(12.08±0.68) mm] was conducted till the early juvenile [60-day age,(129.21±7.69) mm]. According to morphological development, postembryonic development of kaluga was divided in to two different phases, the prelarval stage between hatching (0-day age) and first feeding (9-day age), and the postlarval stage between the initiation of external feeding and organ development completed, the body transparent features disappear, and fins folds anterior to the anus and oral teeth were completely absent (49-day age), then, fish develop into early juvenile[50-day age,(106.78±9.87) mm]. The morphological development and differentiation of prelarvae is obviously faster then postlarvae and juvenile, and all kinds of swimming, respiratory, sensorial and feeding organs during prelarval stage were rapidly developed of the synchronous coordination. Rapid development of those functional organs enabled prelarvae to forage and avoid predator, which contributed to its survival. The differentiation and improvement of bone plate, improvement of fins swimming organs, and occurrence and development of swim bladder were conducted during the postlarval stage, showing that the capability of this stage fish for foraging and avoiding predator was father improving.3. We conducted laboratory experiments with early life stages of H. dauricus, from the middle reach of the Amur River to quantify ontogenetic behavior and compare their behavior with similar laboratory data collected previously on young kaluga from the Amur River. Hatchling free embryos initiated an intense downstream migration that peaked on day1, and continued strongly to day3, and then, decreased strikingly during days4-6, and ceased on day7(8-day migration). Migrants preferred a bright habitat (illuminated and white bottom), open not cover habitat, and swam-up far above the bottom (daily median distance,3.5m). On days21-22, larvae initiated a second downstream migration of similar intensity (four passes per fish per5min), with a peak at34-36days. Juveniles continued a slow intensity migration (one pass per fish per5min) until day66, indicating a long-duration migration style by early life stages. When most free embryos developed into larvae on day9, early-larvae were non-migrant (like late-free embryos), preferring bright and open habitats, and swimming-up far above the bottom until about day35. All life stages (free embryo, larva, and early-juveniles (to day66when observations ceased) preferred a white colored bottom, indicating a strong adaptive need for this habitat feature by wild fish. Later-larvae and juveniles gradually lost their preference for illuminated habitat and also swam nearer the bottom, indicating a shift to a benthic life. Free embryos, larvae and early-juveniles also strongly preferred open habitat, suggesting a similarity in open habitat use by wild individuals of these three life stages. The innate migration pattern of free embryos and larvae was similar in general pattern, but different in some ways from young kaluga previously observed in similar experiments. This result suggests there are at least two breeding stocks with different early behavior in the river. Thus, great care must be taken when culturing fish for stocking during stock enhancement programs to insure the breeding stocks are not mixed, which would produce non-adapted early life stages.4. Four environmental factors (water velocity, substrate, rearing water velocity condition, and diel rhythm) were examined for their influence on migration of H. dauricus early-life stages (free embryos, age0-8day fish; larvae, age9-49day fish; and juveniles, age50-66day fish). Experiments were conducted in six artificial circular-endless-streams creating various combinations of environmental factors to test hypotheses. Velocity regime had a positive effect on migration intensity by free embryos, and further, high velocity delayed the stopping or resting period by late-free embryos and early-larvae. However, migratory free embryos and larvae in different velocity streams still showed they had the drive to migrate a similar distance. Moreover, results suggest a trigger velocity may be needed to initiate or to cease migration. Substrate type had no effect on migration by early free embryos, and had a different affect on larvae depending on age of larvae. Mid-larvae to juveniles reared in a still water tank migrated faster when placed in a high velocity stream tank, showing a compensatory migration, compared to same age fish reared in a high velocity stream tank. This compensation didn’t occur in fish reared in a tank with low velocity (mean,7.2cm·s-1), indicating a trigger velocity may exist between7.2to31.7cm·s-1for compensatory migration. Velocity regime had no effect on diel rhythm of free embryos and juveniles. A fast velocity regime may have indirectly retarded the occurrence of the diel migration rhythm by larvae by retarding fish growth and development. For population enhancement stocking of H. dauricus, the study indicates great care should be taken to insure populations are not mixed during culture. The emergence of compensation migration indicate that the rearing water velocity condition has no effect on the migration of H. dauricus, and the fish reared in still water is still suitable for population enhancement. It is the migrating larvae, not non-migrating or slow migrating juveniles, are stocked to maximize the downstream distribution of stocked fish and reduce competition for foraging resources, and larvae should be released in a river reach with a bottom velocity≥30cm s-1that contains sand-small pebble substrate.5. For the location and size of the fish released, we think it is better to distinguish two stock before specific population enhancement. If larvae are non-migratory, we can release the fish above Fuyuan county, such as Qideli, Zhaoxin and Luobei, even Jiayin and Xunke. The specific location is arranged in the sandy beach and sandy shoal of these above places for reducing feeding competition and enhancing the fishery resources in middle reaches. If larvae are migratory, we can release the fish near Fuyuan county, The specific location is arranged in river reach of Fuyuan county that bottom velocity is greater than30cm·s-1. According to our study results, migratory larvae will accelerate to migrate, so, fish is release earlier the more likely they are added to the wild fish team for migrating. But most of the time, we can’t distinguish larvae are non-migratory or migratory, so, for safety’s sake, we suggest releasing location is arranged in river reach of Fuyuan county that bottom velocity is greater than30cm·s-1, so that migratory larvae can migrate and find suitable feeding sites. Comprehensively consider of the predator, culturing cost and migration factors, we suggest5-8cm (23-36day age) are suitable to release, because this period larvae has well-developed bone plate, enhancing their anti-predator ability, and if this period larvae are mogratory stock, they are still show a migration characteristics. However, a tagging and releasing for effetiveness evalustion is needed to know the survival rate for releasing5-8cm larvae.更多还原