Answer:
By cutting starfish, fishermen are increasing the population of starfish and not decreasing.
Step-by-step explanation:
One of the eccentric characteristics of stars is their ability to regenerate. Basically, if they lose one arm, they'll be able to rebuild another in the same place. In addition, this severed arm will give rise to another starfish. That is, if you cut a star, you will give rise to two starfish.
For this reason, when oyster fishermen decided to cut starfish to lessen competition, they had a bad idea. That's because their goal was to decrease the population of starfish, but by cutting them they will increase that population.