How do we compare and analyze sampling methods?

I would like to survey the amount of black bears that likes salmon. I would survey 50 black bears.
I would record the record by the reaction they have toward the salmon.

Random sample: I would have the zoo keeper randomly select 50 black bears and feed them salmon.
Convenience sample: I would go to the nearest zoo and survey 50 bears.
Biased sample: I will sample the black bears that looks like they would love some salmon.