The Wikipedia Page for Scombroid said:

Fish commonly implicated include tuna, mackerel, mahi mahi, sardine, anchovy, herring, bluefish, amberjack, and marlin.[2] These fish naturally have high levels of histidine,

If this was the problem then the disease was related to the way it was harvested and stored and not the species. Wikipedia did not mention salmon specifically. I wouldn't list it as unique to salmon.

Salmon does have problems. Since salmon feed on other fish they can concentrate mercury or other heavy metals as you mentioned.

There are several places that farm salmon. Reports claim that farmed fish are less healthy than wild caught fish. Environmentalists say salmon farms are rather toxic.

There are several web sites that list sustainable fish. I suspect that the list of sustainable fish differs by region. I do not know where you are located.

A fish that is good in one location may not be good for another location.

The best approach is to find a list of the best fish for your locality.