Uncle Li's family contracted a fish pond. According to scientific breeding, the number of fish in this fish pond should be about 35,000. In order to control the number of fish in the fish pond, Uncle Li cast a net to fish in the fish pond that day, and put marks on the tails of the 400 fish he caught and put them back into the fish pond. A week later, he came to the fish pond again, and this time cast a few more nets, and caught a full 500 fish, only 5 of which had marks on their tails. Uncle Li did the math and decided to catch some fish quickly to meet the requirements of scientific breeding. Do you think Uncle Li's approach is scientific? Approximately how many fish will be caught?
李叔叔家承包了一片鱼塘，按科学养殖，这片鱼塘中养鱼数应在35000条左右．李叔叔为掌握鱼塘中鱼的数量，这天他在鱼塘中撒网捕鱼，在捕到的400条鱼的尾巴上都做好记号后又放回到鱼塘中．一星期后他又来到鱼塘，这次多撒了几网，捕了足足有500条鱼，其中只有5条的尾巴上有记号．李叔叔算了算，决定赶紧捕捉一些鱼，以达到科学养殖的要求．你认为李叔叔的做法科学吗？大概要捕捞多少条鱼？
<gadget id="calculator">5 / 500</gadget>
<output>1/100 = around 0.01</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(1/100) * 1</gadget>
<output>1/100 = around 0.01</output>

<gadget id="calculator">400 / (1/100)</gadget>
<output>40_000</output>

<gadget id="calculator">40_000 - 35_000</gadget>
<output>5_000</output>

<result>5_000</result>