Earlier quoted context omitted.
> "aggressive fishing is the main problem." That is a separate problem from ocean acidification. Ocean acidification is directly linked to pollution from fossil fuel usage.
Yes, aggressive fishing is a different problem (but a problem nonetheless). Ocean acidification however, is caused by the fact that the oceans absorb the excess of CO2 present in the atmosphere; and livestock are responsible for more CO2 production than all of transportation.
There's a common misconception that all CO2 is bad. CO2 is a natural part of the bio cycles found on Earth, what's bad about using fossil fuels is the rapid expansion of CO2 (and other gases) in the environment where life lives, which causes instability and damage as the Earth adapts.