Did a bit more digging:
“The iodine content of fish is quite variable. In general, marine fish have more iodine than fresh water fish, and a significant part of the iodine is in the head of the fish (where the thyroid is). Here are some typical amounts for some common fish, in mcg/100g: Cod (110), Haddock (250), Herring (29), Mackerel (140), Sardines (29), Tuna (30), Atlantic Salmon (76), Rainbow Trout (13). Here are a few ranges to give you a sense of the variability of iodine in fish (mg/100g): Haddock (60 – 920), Pollack (23 – 266), Cod (18 – 1270).”
“Iodine levels in seaweed are quite variable, depending primarily on the type of seaweed. Kelp has the highest amount of iodine, with some kelp granules having 8165 mcg/gm. Most Kelp or Kombu has about 2500 mcg/gm. Other common seaweeds are much lower; for example, Nori (16 mcg/gm), Wakame (32 mcg/gm), Dulse (72 mcg/gm), Hijiki (629 mcg/gm). Iodine content is reduced by storage (e.g., in paper bags or open to the air) and cooking. Most of the iodine in seaweed comes in the form of iodide, but it varies depending on the type of seaweed. Absorption of the iodine from seaweed is variable. Seaweed contains lots of stuff besides iodine, some may be useful (e.g., other minerals) and some may be harmful (e.g., goitrogens like bromide and various chemicals like mercury contaminants). Large amounts of seaweed may be problematic.”
“We are still trying to get accurate information on iodine in Cod Liver Oil. Carlson’s reports none, and the Nutrition Reference Library reports 838 mcg per 100 grams oil. The other companies we have asked did not know, or did not tell us.”
