他们实际上在观测鱼向上游的迁移活动。
They actually monitor the movement of the fish going up river.
图3 b：[左下]横条说明向上游的移动是被禁止的。
Figure 3b: [bottom left] Crossbar indicates upstream movement is not permitted.
他向上游游去，但还是被水冲了下去，流速比他预料的要快得多。
He swam quartering upstream, but still was swept downward rather faster than he had expected.
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