Fishy puzzle [Ended, with solution]

Solution:
My intended solution was this:

1. Find solution for 1,2,3,4 fish by hand: 1 fish: 1, 2 fish: 2, 3 fish: 5, 4 fish: 15.
2. Search for the sequence "1,2,5,15" with Google or OEIS to find Bell numbers sequence.
3. Use a list of Bell numbers to find answers.

But as you can see in the discussion here there were more ways to solve the puzzle, some of which turned out quite creative. Congrats to all solvers!

Answers: #1, #2.

so i was an idiot, who tryed to solve it himself, instead of just using google =)

Guess my googling skills aren't quite good enough yet. Oh well, at lesat I approxiamted it between 400 and 500 correctly.
Tried Wolfam Alpha too

I use Excel to calculate get 4.63859E+18. :)

XD