Eating fish

It's complicated.
It can come from different species, stocks, gears, vessels, countries, processes, certifications...
There is not only one rule.
And each rule should be adapted for the context.
The facts are changing all the time, needs continuous revision.
What to do?
Sorry...I do not have an answer.
Only comments that help to guide the choice.
If my PhD, and 4 years of my lifetime, will help in some way, I would be a veeeery happy women.