FishVille: A Discovery Log Guide for Ichthyologists
Here's are the current fish collections and what you need to do to get 'em:
Classic Fish: Shy Hamlet, Hawaiian Hogfish, Percula Clownfish, Swissguard Basslet, and Pinktail Trigger
Tip: All fish can be bought at the store, except for "Pinktail Trigger", which is only available on the Free Gifts page.
Anthias: Townsend Anthias, Tierra Anthias, Lyretail Anthias, Thompson Anthias, and Red Striped Anthias
Tip: These are all on the Free Gifts page, but there's a catch -- each one is only giftable on certain weekdays, from Monday through Friday! So you need a friend to send you "Townsend Anthias" on Mondays, "Tierra" on Tuesdays, "Lyretail" on Wednesdays, "Thompson" on Thursdays, and "Red Striped" on Fridays.
Shrimp Gobies: Prawn Goby, Flagtail Shrimpgoby, Giant Shrimpgoby, Wheelers Shrimpgoby, and Widebar Shrimpgoby
Tip: Except for the "Prawn Goby", which costs 90 Coins, all these fish must either be bought for Sand Dollars at the store or hatched by a "Mystery Goby Egg" from the Free Gifts page.
Tip: Click on the Mystery Fish in the Discovery Log to take you to the Fish Mastery page. You can only get these fish by doing the Fish Mastery, which means you've got to buy a certain type a fish and sell 'em a certain number of times. Check out the Fish Mastery guide for complete details.
For the Treasure Collections, see: FishVille: A Discovery Log Guide for Treasure Hunters