Alex - discussions I've read on the topic of canned fish typically state... Wild is always better than farmed. Same reasons as for fresh fish.
But, some fish are wild and still have the heavy metal issue depending on where they live and how polluted the waters are plus how large they become... meaning with age, more chance to accumulate the heavy metals. The smaller the fish, the less risk. For example. Sardines = low risk. Grouper - high risk for heavy metals.. same with shark, tuna, etc.
Another issue with canned, though, is the can's internal coating that contains BPA which is considered the environmental toxin that is an endocrine disruptor. There are canners that are now using BPA free cans... I saw canned wild sardines with the box labeled as BPA free. If you don't use much canned food, that's probably not a huge threat, but consuming a lot of canned food regularly, poses a significant risk.
The salt content is definitely a consideration for everyone and especially afibbers. Fresh fish doesn't have the added salt consideration.
As Gordon mentions some retailers offer lower sodium products. My local grocer/owners have their own house brand for packaged foods with specifications for no or low salt on many items because their focus is to be a be a nutritionally oriented food store. Sort of an oxymoron, though, because the majority of the food space in the store is for packaged, processed foods... albiet, with lower salt and BPA-free cans on some items. But they have organic meat and fresh produce and wild-caught fish which is a plus.
Jackie
