摘要
1.汉江产漂流性卵的鱼类至少有25种,其中经济鱼类有草鱼、青鱼、鲢、鳙、鯮、鳤、鳡、长春鳊、赤眼鳟、铜鱼、吻鮈、鳜以及三种红鲌属鱼类。2.产漂流性卵鱼类开始产卵的水温分别在16—20℃之间,经济鱼类多在18℃上下。产卵时需要有江河的涨水过程。在河流涨水的诸水文要素中,流速的增大,对促使产卵起着主要作用。不同的鱼类产卵时对流水的要求是有差异的。鱼类的产卵规模与江水的流速增大紧密相关。3.丹江水库建成后,上游的产卵场有前房、天河口和安康等10处。中游有钟祥和马良等7处,支流唐河、白河也有产卵场。就总产卵量来看,上游1977年为1745.9亿粒,中游1976年为47亿粒。上游为中游的37倍。其中,四种家鱼的产卵量,上游为171.3亿粒,中游为9.3亿粒。4.丹江口水利枢纽对汉江上游产漂流性卵鱼类繁殖的影响,主要表现为给上游提供了规模较大的繁殖群体。另一方面,由于主要产卵场分布在接近水库的江段,致使占上游总产卵量90%的鱼卵在孵化前随江水流入水库,有一部分鱼卵会受到损失。对中游的影响主要是由于水库的低温水和大坝对径流的调节,改变了中游的水文条件,导致产卵场的变迁,繁殖季节推迟和产卵规模缩小。总的来看,对上游的影响明显的有利,对于中游则不利的影响要多一些。5.根据产漂流性卵鱼类繁殖的生态习性和汉江的条件,可以认为,在汉江和类似汉江的条件下,兴建水利枢纽可以不必附建过鱼建筑物。为了充分发挥水体的渔业效益,水库区应做好渔业规划,加强经营管理。水利枢纽的下游需充分重视改变了的水文条件,特别是低温水对鱼类生活的影响,以采取补救措施。
Hydrological conditions of the Han River display obvious change with constructing
dams for the hydroelectric stations. In order to show how far the spawning of fishes is
affected from the change of the hydrological conlition, an ecological investigation was
carried out in 1976 to 1978. The results are summarized as follows.
1) There are 25 species of fishes which cast their 'drifting' eggs in the Han
River. The most common ones are Ctenopharyngodon idellus, Mylopharyngodon piceus,
Hypophthalmichthys molitrix, Aristichthys nobilis, Elopichthys bambusa, Ochetobius
clongatus, Leuciobrama macrocephalus, Parabramis pekinensis, Squaliobarbus curriculus,
Corcius heterodon, Erythroculter spp., Rhinogobio spp., Siniperca spp., etc. Nearly all
of them are commercial fishes.
2) The water temperature and current velocity of the spawning ground seem to be
the essential factors for fish spawning. The commercial fishes begin to spawn at the
water temperature of 16-20℃, while the four farm-fishes above 18℃. The increase
of the current velocity may be regarded as the essential factor that induces the fishes to
spawn but these seem to have differences between different species of fishes.
3) Since the establishment of Danjiang Reservoir, there are ten spawning grounds
in the upper course of the Han River, seven in the middle course and in its branch, the
Tangbai River, have been found. The amount of the eggs laid during the whole breeding
season are calculated at 174590 million in the upper course in the year 1977 and about 4700
million in the middle course of the year 1976. The eggs laid by the four farm-fishes
are calculated at about 17127 million in the upper course and 230 million in the middle.
4) In the lower part of the upper course of the Han River the better condition
of spawning grounds provides many spawning grounds for 'drifting' eggs fishes to
spawn, but the eggs soon pass into the stagnant water of the reservoir where the eggs pos-
sibly sink to the bottom then make a serious damage in the development of the embryos. In
the middle course of the river, hydrological condition may be highly altered owing
to the presence of the reservoir, the water flow out from the hydroelectric station being
colder and thus cause the spawning ground reduced in area and much retarded.
5) Because of the habits and habitats of the fishes which live in the drainage of
the Han River, it seems that it is unnessary to install any kind of fishpass on the
dam of the reservoir.
