Fish
Buy sustainable or organic

Look for the Marine Stewardship Council logo to ensure fish is sustainable.
If you do buy farmed fish, buy RSPCA Freedom Food or Soil Association organic for higher welfare standards.
Otherwise fish may have suffered in over-crowded tanks, experienced unacceptable periods of starvation and been slaughtered inhumanely.
For further reading, please visit the Greenpeace UK seafood FAQs...