GMAT Sentence Correction (SC) | Around 1900, fishermen in the Chesapeake

So basically, this fisherman question, like the honeybee question, is merely stating facts ("narration" as Ron called it) - that at 1900, this was the scenario, then fastforward 20 years later, 1st event (i.e. overfishing +building) happened and resulted in another scenario. Same for the honeybee, after their release, then the first event (i.e. migration) happened. Therefore, this is the exception to the past perfect>>past tense rule.