To better encourage people to fish for Catch of the Day, maybe it should give 3 times the XP, plus 1 XP for every consecutive day up to 30, just like with gold. For instance, suppose the fish to catch is the firecuda, which gives 11 XP (or 1100 if it's the first one). If you have been doing the Catch of the Day for 10 days, that would be 43 XP per fish (11 x 3 + 10). If it happens to be the first fish of its kind that you catch, it would be 3310 XP (1100 x 3 + 10). Now, suppose you're maxed out when you catch a firecuda today. That would be 63 XP per fish (11 x 3 + 30). That's still not very much compared to the first time you catch a type of fish, but it should help with the rank grinding considerably.