this may have been answered, but I just hit about 175 and was trying Feralas for nightfins with the +100 lure. I got there about 22:00 server time and per the loot schedule, I caught salmon and nightfins, at a ratio of about 3 to 1 (less than an hour fishing so stats are not perfect). I had no empty loot windows. I logged on a bit later, ~0:05 ST when only nightfins were supposed to drop, and almost immediately got empty loot windows -- maybe 20% of the time. But I was catching the normal amount of nightfin. Also I got 4 skill up points when no loot window showed up after a "catch". No loot, but skill ups. I suspect that the scripting is calling for a legitimate catch, but due to the time period, Salmon are not in the loot table, so no loot window is launched. But the skilling up shows that a catch is registered. So from this limited experience (about 40 minutes of fishing), I wouldn't worry about the missing loot windows as nightfins and skilling don't seem to be affected.