My wife comes from a culture where preparation and eating of dried fish is very common (as long as one takes the proper measures to deal with the smell). She prepared for me recently a serving of dried mackerel, but it was sooooo salty that I could only bear to eat one or two bites. Can anyone recommend some sort of preparation method to counteract this excessive salty flavor?
The standard way to cook salt cod for dishes where you want to really remove the saltiness, such as brandade, is to soak it (for hours) in a couple of changes of water, and then simmer it in milk for half an hour to an hour. This might work with the mackerel. Not sure what you'd use it for after that, though.
As FuzzyChef indicates in his answer, the standard way is to soak in abundant cold water. The number of hours depends on the thickness of the piece. Some cod can be soaking for 48h with a change of water every 8-12h.
But, there is no need for simmering the fish in milk. You can use the fish as usual once the desired saltiness is reached.
I lived in Japan for eight years and have a Japanese wife. The reason the Japanese cook rice with no seasoning is because so many of the preserved foods they eat are so salty. I developed the habit years ago of eating large bowls of unseasoned rice along with small servings of salt preserved fish and vegetables. I might point out that the Japanese are among the longest lived people in the world so perhaps there is merit to this eating system.
Granny to the rescue:
Depending on the recipe this is how my grandmother got rid of excessive salt in soup (so if boiling, this will be of great help)
Add potatoes cut in 4 lengthwise to the water: as they have a large surface-to-volume ratio, they will soak up lots of salt.
You can serve them both with the meal or you can keep them in the fridge to make potato salad next day.