Did you just pass 105 Fishing? The quests "reset" when you pass this milestone, to catch dungeon fish.
It is possible to get single count fishing orders with high loyalty withe the fish mongers. You have to have filled single line orders of 10, 15, and 20 for a particular fish, before the system will allow you to get the second line. If you have not filled those orders, than you will get the single line orders. I record my fishing quests/rewards. Looking at the data, my 254th quest (20 King Crab) and 258th quest (20 Pumpkinseed Sunfish) were single line orders (after getting to 105 fishing). There are 42 types of fish/crabs/lobsters (not including dungeon fish) which can be requested. Since there are 3 types of single line orders (10,15,20) which must be completed, that is 126 possible single line orders for your fisherman to get. Including the 12 dungeon fish, the possible single line orders goes up to 162 (54 total types of fish/crabs/lobsters).
The only way to get past the single line orders is to get them and fill them. You probably have a decent stockpile of fish, so they should be a quick turn around.
Stayin Alive,
BG