In the third paragraph, which line explains why lionfish must be handled carefully?

To combat the invasion, wildlife agencies have sponsored lionfish derbies.
In these derbies, local scuba divers are invited to harvest lionfish.
Lionfish have to be handled carefully because of their venomous spines, but they are apparently delicious.
However, scientists estimate that more than a quarter of the population would have to be taken every month to stop the growing population.