susie
Once a week should be fine.
Swordfish has the highest concentration of Mercury [using maximum concentration found, not average].
Swordfish had 0.97 parts per million versus Salmon which had 0.01 parts per million. Albacore tuna had 0.35 parts per million, and chunk light tuna had 0.12 parts per million. Catfish and Shrimp were only a little higher than Salmon -- coming in at 0.05 parts per million.
It is more the case of bigger fish eating smaller fish that helps to concentrate the mercury.
Thanks for the info. I don't like fish all that much, but shrimp! Good thing I can't afford it often! Whoda thought being poor would be a blessing? :)
susie