The other day an anonymous querent wondered about the correct way to say “Thanks for the salmon!” The answer is: that depends.
If you mean that you are grateful for an entire salmon, then the word you want is a masculine word ending in a soft sign: лосось. If you mean that you are grateful for a filet of the fish which you intend to consume as food, then the word you want is a feminine word: лососина. Thus:
|Спасибо за лосося.||Thanks for the [whole] salmon.|
|Спасибо за лососину.||Thanks for the salmon [flesh].|
Actually лосось can also mean simply the flesh of the animal, but every once in a while you will meet some pedant who will want you to distinguish the two words.
In the US one associates salmon particularly with the the states of Alaska, Washington, and Oregon. In Russia Камчатка is the major нерестилище of salmon. A нерестилище “spawning ground” is a place where fish lay their eggs.