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首页> 外文学位 >Movement, reproduction, habitat use, trophic status, and the fishery of Labeo victorianus in Lake Victoria (Tanzania).
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Movement, reproduction, habitat use, trophic status, and the fishery of Labeo victorianus in Lake Victoria (Tanzania).

机译：维多利亚湖（坦桑尼亚）的Labeo victorianus的迁徙，繁殖，栖息地利用，营养状况和渔业。

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A study on the fishery, reproductive cycle, trophic status, movement patterns, and habitat use by Labeo victorianus was carried out in the Speke and Mwanza gulfs, Lake Victoria, between October 1999 and September 2001. Labeo victorianus locally known as ningu, is an endemic fish species of the Lake Victoria basin, now considered a threatened species.; The fishery of ningu is carried out near river mouths where they are intercepted during the rainy season on their annual spawning migration. Although fishermen still catch adult ningu, their decline in fishermen's catches since the early 1950s can be attributed to recruitment overfishing, environmental degradation, reduced food resources, blocked access to spawning grounds and little enforcement of fisheries regulations.; Currently, monitoring of ningu fishery and other nearshore fish resources is poor because of few fisheries personnel, lack of working facilities, few beach fish recording stations and much emphasis being directed towards the Nile perch fishery, which brings the country much-needed foreign exchange.; Ningu is very fecund, producing up to 270,000 eggs. In the Speke Gulf, ningu mature earlier than those living in the northern part of Lake Victoria and have two spawning peaks coinciding with the two rainy seasons. Most ningu spawn during the long rains (February to May). The presence of spent individuals in the lake suggests that ningu now heavily blocked by nets and reed fences from migrating into spawning ground upstream and flood plains, could be spawning in the lake.; Currently is absent in offshore waters, spends most of the time in rocky habitats and under vegetation cover, and performs restricted movements, perhaps because of the presence of another predator, the Nile perch, that was the introduced into the Lake Victoria since the late 1950s and 1960s. Other populations of ningu have been found in satellite lakes in the basin. The recent signs of recovery of Ningu and other threatened fish species of Lake Victoria has coincided with the decline in catches of the Nile perch since the mid 1990s.; Stable isotope analysis reveals that there are several populations of ningu, and that ningu is a primary consumer, feeding mostly on benthic algae. However, the benthic algae production is now threatened by eutrophication, and some of the satellite lakes are being heavily encroached. The recovery of Ningu and other nearshore fish communities of Lake Victoria calls for proper enforcement of fisheries regulations and curbing all human-related activities that contribute to environmental degradation of nearshore habitats and the satellite lakes, where ningu and other threatened fish species now take refuge. The recently established village based Beach Management Units (BMUs), as part of co-management of fisheries resources of Lake Victoria, will be more effective only if they continually get logistical support and scientific advice from the Tanzania Fisheries Division.
机译：在1999年10月至2001年9月之间，对维多利亚湖的Speke和Mwanza海湾的 Labeo victorianus 进行了渔业，生殖周期，营养状况，运动方式和栖息地利用的研究。 > Labeo victorianus ，当地人称为ningu，是维多利亚湖流域的特有鱼类，现已被视为濒危物种。宁古的捕捞活动是在河口附近进行的，在雨季每年的产卵迁徙过程中都将其捕捞。尽管渔民仍在捕捞成年的人，但自1950年代初以来渔民捕捞量下降的原因可归因于招募过度捕捞，环境退化，粮食资源减少，产卵场的通行受限以及很少执行渔业法规。目前，由于渔民少，工作设施少，滩涂鱼类记录站少，尼罗河鲈鱼渔业偏向尼古河鲈鱼渔业，因此对尼古河渔业和其他近岸鱼类资源的监测工作很差，这给该国带来了急需的外汇。 ; Ningu产卵量很高，最多可产27万个卵。在斯佩克湾，宁古比居住在维多利亚湖北部的古纽早成熟，并且有两个产卵峰与两个雨季相吻合。大多数宁古人在长时间的降雨（2月至5月）期间产卵。湖泊中有一些枯萎的个体，这表明现在被网和芦苇篱笆严重阻塞而无法迁移到上游产卵场和洪泛平原的宁古可能正在湖中产卵。目前不存在于近海中，大部分时间都在多岩石的栖息地和植被覆盖下，并且活动受限，这可能是由于存在另一种捕食者尼罗河鲈鱼，该鲈鱼自1950年代后期被引入维多利亚湖和1960年代。流域的卫星湖中还发现了其他的宁古族。自1990年代中期以来，最近恢复的Ningu和其他维多利亚湖濒危鱼类的迹象与尼罗河鲈鱼产量的下降同时发生。稳定的同位素分析显示，宁古有几个种群，并且宁古是主要的消费者，主要以底栖藻类为食。但是，现在底栖藻类的生产受到富营养化的威胁，一些卫星湖正受到严重侵蚀。 Ningu和维多利亚湖其他近岸鱼类群落的恢复要求适当执行渔业法规，并遏制一切与人类有关的活动，这些活动会导致近岸生境和卫星湖的环境退化，在此之前，ningu和其他受威胁鱼类已成为避难所。作为维多利亚湖渔业资源共同管理的一部分，最近建立的以村庄为基础的海滩管理单位（BMU），只有在他们不断获得坦桑尼亚渔业部的后勤支持和科学建议的情况下，才会更加有效。

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