Not a lot of people know this but species-rich, undamaged marine ecosystems actually draw down CO2 and sequester it through natural processes, which is very good in the fight against climate change.
Over-fished marine ecosystems can cause greenhouse gas emissions in several different ways, including through destructive fishing methods such as bottom trawling – alarmingly so according some scientific estimates which put bottom trawling in the same league as aviation when emissions are counted.
Haddock was over-fished for decades but recent changes in fishing quotas have allowed the fish stocks to recover and haddock from UK waters – found in fish fingers and chip shops – is a good sustainable choice. For everything else, demand the blue Marine Stewardship Council sustainability tick stamp of approval.
Resource for Sustainable Fish
How to buy sustainable fish (Which?)