We call it BBQ grilled salmon but it probably should be called "grilled salmon", not BBQ, since no BBQ sauce or rub is used in this recipe. We will leave that to the BBQ enthusiast to figure out. What we do know is that this is one of the best ways to cook salmon.
While frozen salmon (or previously frozen) is more available and somewhat cheaper, if you can get fresh salmon it will make "good" turn into "unbelievable". If you are accustomed to frozen salmon or have never tasted "fresh", you will not believe the difference. They are almost like two different types of fish.
Having said that, do not think you must have fresh salmon to enjoy this recipe. Frozen also makes an excellent, tasty grilled salmon. Fresh, if you can get it, is simply better.
And..if you are unable to find fresh tarragon and dill you can substitute dried (bottled spices) as needed.