If you're not in the Cove for dil and you're just skilling up/making money try Nash. As I said in my other post I had the same problem today but in Nash, went to the Cove and it was fine. I didn't SS it but I went 12 "You didn't catch anything" -> Merc -> 7 more "You didn't..". Nash/Cove can suck even on good moon phases.
Fishing hole is depleted. Somebody(s) came through and cleaned the place out, and now it has to repopulate. One of the checks SE tried to put in place to prevent over-fishing. Come back in an hour, see if you do better.