The amount of fish (and other marine animals) we eat is not sustainable anymore. We eat more fish than the oceans can produce, more than 90% of the fish populations is overfished. That should be reason enough to reduce or stop the consumption.
The fish we eat is often not so healthy as we think. A lot of fish we eat (especially the carnivourous fish that are high in the food chain and often on our menu) contain heavy metals in large quantities and PCB’s, causing cancer. If we eat more than 2 ’fat’ fish every week, we exceed the toxicological accepted limits of these substances. Fish oil makes no difference (note: to make 1 litre fish oil, 20 kg fish is needed).
An important reason why fish is healthy is the fact that it contains the essential Omega-3 and Omega-6 fatty acids. However, fish does not make these acids itself but receives it from the algae it eats. These algae are available in eco-supermarkets or on the internet e.g Amanprana-Okinawa-Omega 3,6,7,9 (Noble House). There is also a lot of other healthy food that contains Omega-3 and/or Omega-6.
Are there any sustainable alternatives? Sorry, not really, read Overfishing and destructive fishing techniques .
If you persist to eat fish, fish guides for your area can help selecting the ecological better and more durable caught fish. Note – yet these guides are a snapshot. The scarcity of species can change rapidly over time since most fish stocks are under continuous threat.
Fish guide UK: http://www.goodfishguide.org/
App for fish guide: http://www.goodfishguide.org/information/mobile+app
Fish guide Germany: https://issuu.com/greenpeacede/docs/greenpeace_fischratgeber_2016
Fish guide the Netherlands: http://www.goedevis.nl/
App voor viswijzer: https://itunes.apple.com/nl/app/viswijzer/id377191753
International (including USA/Canada): http://www.greenpeace.org/international/en/campaigns/oceans/which-fish-can-I-eat/alternative-fish-guides/#a0