usually ankimo tends to be offered in the colder winter months. i'm topping this thread because ankimo showed up (unexpectedly!) in the sensei's appetizer plate at, of all places, yakitori boy. $7.50 if you want just a portion of the monkfish liver itself.
There is no season in that sense. The weather was hot.. When it cools like this past week it comes around. So it is available basically throughout the year, give or take pending on temp. Not around during the summer.