Removing the mud, uncovering gravel beds where fish spawn, and finding suitable salmon types to rebuild the population is a daunting task.
清除淤泥，发现鱼类产卵的砾石层，找到合适的鲑鱼种类来重建种群是一项艰巨的任务。
There are biologists throughout the state constantly monitoring adult fish as they show up to spawn.
整个州都有生物学家在成年鱼出来产卵的时候持续监测着它们。
Some fish do not spawn until maturity. If you catch them before that and you've no baby fish produced for the next year.
有些鱼要到成熟期才产卵。如果你在成熟期之前就开始捕捞，那么你明年就没有鱼籽了。
Some fish do not spawn until maturity: catch them before that and you've no baby fish produced for the next year.
一些鱼在成熟之前是不产卵的：在些之前逮住它们，就不需要担心下一年鱼籽的产量。
Blocking a river with a dam blocks the movement both of fish upstream to spawn and of silt downstream to fertilise fields.
建堤坝来阻断河流，既阻挡了回流产卵的鱼，又阻碍了下游淤泥肥沃土壤。
Blocking a river with a dam also blocks the movement of fish upstream to spawn and the movement of silt downstream to fertilise fields.
用大坝阻断河流使得鱼类无法逆流而上去产卵，同时淤泥无法顺流而下去肥沃土地。
And some doubt the fish will ever make it into the lakes, given their need to spawn in long, fast-flowing rivers like the Illinois.
有些人还怀疑它们是否真的能进入湖泊，毕竟他们需要在像伊利诺斯河那样的湍急水流中产卵。
But this year, fewer fish are coming into the Volga delta from the Caspian Sea to spawn.
但今年，从里海来伏尔加河产卵的鱼群数量减少了。
Some fish are radio-tagged, moved above a dam, and tracked to find out if they return to their birthplaces to spawn.
有些在水坝上活动的鱼被安上了无线电标签，可以追踪查看它们是否返回出生地产卵。
Four of the world's 10 biggest freshwater fish migrate up the Mekong to spawn.
世界十大大型淡水鱼中有四种会迁移至湄公河产卵。
The number of indigenous fish was falling, since the floods that induce them to spawn were becoming rarer.
本地鱼的数量同样在降低，因为引诱它们来产卵的洪水变得更加不常见。
They feed primarily on insects and spawn in shallow water in the spring. Pollution of streams has reduced the Numbers of this excellent food fish.
主要以昆虫为食。春季在浅水区产卵。由于溪流受到污染，使这种极佳的食用鱼数量减少。
Salmon spawn in fresh water, but in many cases, the fish spend most of their lives at sea, returning to the rivers only to reproduce. This lifecycle is described as anadromous.
虽然作为淡水鱼类，三文鱼大部分时间都生活在海洋里，它们只在产卵期间回到淡水中，这种生活习性被称为溯河产卵。
The wild fish captured in spring can spawn in autumn by use of reproductive control method. The viable egg rate is 23.4%.
借助生殖调控措施，春、夏季获取的野生鱼秋季就可产卵，好卵占23·4%。
With the control of ecological factors, fish can be induced to spawn synchronously with average rates of fertilization and incubation reaching 80 9% and 76 3% respectively.
运用人工调控环境因子和使用适宜的促熟与催产的方法，能诱导雌雄亲鱼性腺发育同步，平均受精率为80 9% ，平均孵化率为76 3 %。
With the control of ecological factors, fish can be induced to spawn synchronously with average rates of fertilization and incubation reaching 80 9% and 76 3% respectively.
运用人工调控环境因子和使用适宜的促熟与催产的方法，能诱导雌雄亲鱼性腺发育同步，平均受精率为80 9% ，平均孵化率为76 3 %。
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