The other thing to look for is radiation from Fukushima in your fish. I use Nordic Naturals Omega-3 + D, thinking of switching to their cod liver oil, which their web site says is 100% arctic cod.
http://www.nordicnaturals.com/consumers.php
If you find another brand with similar quality, lower price, please let me know.
Carlson’s is cheaper and is IFOS guaranteed.
https://www.amazon.com/Carlson-Norwegian-Cod-Liver-Lemon/dp/B003B3P4PO?th=1