Answer:
The trait small fins will disappear. This is, eventually, there will be no more fish with small fins
Explanation:
Because long fins are being positively selected in nature (positive natural selection), the small fins will eventually (over time) disappear. That is, there will be no more fish with this characteristic, there will be no more fish with short fins.
The above is unavoidable unless there is a good trait (another) linked to the small fins. If there is a good characteristic linked to small fins, that good trait will keep the short fins in the population.
