Survival of juveniles can be increased slightly based on research on similar species. Lions kills a significant number of juveniles each year. If the number of lions was reduced, the number of kills would also be reduced. Unfortunately there are many other source of mortality so reducing the lions does not remove all juvenile mortality. Allow a hunt for a limited number of lions each year, reducing the lion population.
Costs are fairly minimal.
Hunters can pay for the opportunity to hunt a lion, covering most of the costs, other than the costs of enforcing the limited hunt. Increasing the survival of adults. Survival of adults can be improved based on tests with other species. Poachers kill a large number of adults for their value in foreign markets. Hooves, tails, and bones are used as components of medicines.