can i fry fish in olive oil

Yes

Fish fried in olive oil is lovely. As olive oil tends to lose some of its flavor when heated, it would be wiser - at least more economical! - to use a "lower" quality olive oil. in other words, not the $26 extra-virgin cold-pressed organic variety!

In fact "poaching" fish in olive oil works really well too if its a firm fleshed fish, like say halibut or tuna.

I do it all the time. The answer is yes, you can. Please don't overcook the fish, though. If it flakes, it's overcooked!

I sauté fish (especially salmon) in olive oil all the time. You can even make marinades for fish using olive oil. Just be mindful of the lower smoke point of olive oil compared to vegetable/peanut oil. Then again, fish cooks so quickly that you don't even need to worry about the temperature of the oil. Fry and enjoy!

Deep frying in olive oil is usually done in Southern Spain&Portugal.

Yes