What has been stated by the Devs Note that there are the following: 6 types of quest crabs 6 types of quest lobsters 12 types of Shallow Water Fish 18 types of Deep water fish 12 types of Dungeon fish 42 seas + 12 Dungeon fish Prior to a certain skill level^ (somewhere between 100 & 105), you have to fill quests for the 42 different types of non-dungeon fish, to have a high chance of getting additional lines beyond the first. There's some speculation that it might be tied into being scrolled higher than 105. ^ Once you hit that trigger point for the dungeon fish (which actually occurs after you can start dungeon fishing, but BEFORE you can actually get quests that ask for them), the 12 Dungeon Fish get added into the calculation. The calculation to see if a quest gets additional lines appears to be: X: Current number of lines in the quest calculation. F: Fish types for which you have filled at least X number of quests for. Y: Number of Fish types included in the calculation. This starts out at 42, then goes up to 54 at some time in the low 100s (see ^ above) Z: other variables that MIGHT exist. Z might not actually exist at all, or be based on one's reputation, or exist simply to make sure that you don't have a 100% chance to upgrades (as after a certain point without it, a fisher could get to where all quests are 6 lines) F/Y * Z = chance to jump to the next tier. IF you do get another line, X increments by 1 (up to 5), and the F number is recalculated, for determining if the quest goes up again. The calculation for 6 lines (occurring after rising to 5 lines) results in either the quest staying 5 lines, or simply jumping up to 6 (no calculation for further lines) So, if you'd done enough quests to where you'd - Done at least one quest for all crustaceans, shallow water and deep water fish Done at least two quests from all but 2 crustacean types and 1 shallow water type. Done at least three quests for 6 crustaceans, 9 shallow fish and 16 deep fish Done at least 4 quests for 4 crustaceans, 8 shallow fish and 14 deep fish Done at least 5 quests for 2 crustaceans, 6 shallow fish and 10 deep fish Example 1: This would be prior to the addition of the dungeon fish Results: Your quest has at least 1 line *The chance for a second line is 42/42 (or 1.0) * Z **If the line above results in a second line, then the calculation for chance for 3 lines would be (10+11+18)/42 * Z, or 39/42 * Z ***If the line above results in a third line, then the calculation for chance for 4 lines would be (6+9+16)/42 * Z, or 31/42 * Z ****If the line above results in a fourth line, then the calculation for chance for 5 lines would be (4+8+14)/42 * Z, or 26/42 * Z *****If the line above results in a fifth line, then the calculation for chance for 6 lines would be (2+6+10)/42 * Z, or 18/42 * Z Example 2: This would be after passing the point where the dungeon fish are added to the calculation, but before you actually fill any quests that call for them. Results: Your quest has at least 1 line *The chance for a second line is 42/54 * Z **If the line above results in a second line, then the calculation for chance for 3 lines would be (10+11+18+0)/54 * Z, or 39/54 * Z ***If the line above results in a third line, then the calculation for chance for 4 lines would be (6+9+16+0)/54 * Z, or 31/54 * Z ****If the line above results in a fourth line, then the calculation for chance for 5 lines would be (4+8+14+0)/54 * Z, or 26/54 * Z *****If the line above results in a fifth line, then the calculation for chance for 6 lines would be (2+6+10)/54 * Z, or 18/54 * Z This is why 1 and 2 line Quests make a sudden resurgance after the point in Example 2 is passed: a. The chance for 2 lines drops from 100% * Z to 70% * Z b. The chance of a 2 line becoming a 3 line drops from 92.86% * Z to 72.22% * Z c. The chance of a 3 line becoming a 4-line drops from 73.81% * Z to 57.41% * Z d. The chance of a 4 line becoming a 5-line drops from 61.9% * Z to 48.15% * Z e. The chance of a 5 line becoming a 6-line drops from 42.86% * Z to 33.33% * Z (or, effectively, the existing percentages were multiplied by 7/9, since the the number off possible fish was multiplied by 9/7). As you fill quests with dungeon fish, the reduction slowly goes away. But, it can be jarring to suddenly go from quests for 5-6 fish (4 of which are deep water) to suddenly getting quests again for 1 or 2 shallow water fish.