This is false on many levels. In 2016, the last year of Obama's presidency, Maine recorded a record lobster catch of more than 130 million pounds, which was worth a record $538 million.
Here's the lobster catch in the years leading up to 2016. Not that Obama had anything to do with it, but the lobster catch surged during his presidency. 
The opposite has been the case since Trump took over. While the lobster catch, and value, have remained relatively high for the first three years of Trump's presidency -- historically speaking -- both landings and value have been lower than during Obama's last year in office.
Moreover, the tariffs imposed by Trump on China, and their retaliation, have only made matters worse for lobstermen.
pressherald.com/2019/08/23/chi…
pressherald.com/2019/08/23/chi…
This year has been among the worst in a long time for lobstermen, as the market for lobster has cratered during the pandemic.
Trump appears to be referring to his recent decision to allow commercial fishing in the East Coast's only marine monument, which Obama created during his last year in office.
However, there's only a small amount of lobster fishing that occurs in the protected area, and few of the lobstermen are from Maine. The marine monument is 130 miles southeast of Cape Cod.
To learn more about the region's lobster industry, check out lobsterwar.com.
And this: President Trump tweets about Maine lobster, orders financial help for industry wgme.com/news/local/pre…
Also, worth noting, is that one of the primary reasons for the surge in the lobster population over the past decade has been the warming waters in the Gulf of Maine, which have warmed faster than nearly any other body of water on the planet. Trump thinks such warming is a hoax.
Fact checking Trump’s claims about the Maine lobster industry, the story version:
bostonglobe.com/2020/06/25/nat…
bostonglobe.com/2020/06/25/nat…
