Fish delivers an impressive dose of omega-3 fatty acids that our bodies need to grow and thrive, and vitamin B12, in addition to other substances.
Prefer small seafood at the bottom of the food chain—for example, anchovies, sardines, and herring—are more plentiful than their larger cousins, grow more quickly, and contain fewer contaminants, making them sustainable and healthy choices.
We might prefer small blue fish, which contains an amount of selenium (one of the properties of selenium is to counteract mercury contaminant, binding it to an inactive compound). A list of small blue fish could be easily found on internet, in your language.
A wonderful local trout (rich on vitamin B12 more then all other food, see my post on it) fished in a small alpine lake like in Engadin is the best choice for our health.
Try to avoid the varieties, which may suffer from overfishing, heavy mercury load, and/or other problems: Chilean sea bass, Atlantic cod, grouper, imported king crab, king mackerel, orange roughy, Atlantic salmon, imported shrimp, swordfish, and Atlantic Bluefin tuna.
Prefer seafood fished at sea or lake or river (only in clean waters) but not farmed. Farmed fish often feast on pesticides, antibiotics or other substances.
To be up-to-date with the clean waters of our ocean/sea consult for example this link below (select clean waters score for the country you want to know about): http://www.oceanhealthindex.org
The image of the trout is taken from this website, Swiss Fisheries Consulting Office ( in DE, FR, IT): https://www.fischereiberatung.ch/index