Hello, Yaelle

About Fish Tycoon on your Mac, the following might help you be able to play it again

It's likely that your Fish Tycoon savegames and preferences were stored in a location where the game cannot find them. That most often occurs when upgrading from the original version of Fish Tycoon to the Universal Binary version of Fish Tycoon, since the two versions store the savegame files in different locations. To determine which version of the game you are running, look in the lower left corner of the game's Menu screen. Version 1.51 is the Universal Binary version and uses the location ~user/Library/Preferences/LDW/Fish Tycoon to store the savegame files. Earlier versions (e.g. 1.00) store the savegame files in the folder where the Fish Tycoon application is located. When you launch Fish Tycoon, the savegame files must be in the correct location, or the game will be unable to load them and will simply start a new game when it's launched. You should be able to find your previously saved game(s) and put them in the proper location for the version of Fish Tycoon that you're running by following these steps:

Search your computer (using something like Spotlight or Sherlock) for files called FishTycoon**.ldw (where ** is a number). Note that there is no space in the filename, unlike the game's folder and application bundle name. There may be up to 11 of those files, depending upon how many player slots you were using. The single-digit numbers are your "primary" savegame files and are numbered 1-5 (corresponding to the player slots). The two-digit numbers are the "backup" savegame files, and are numbered 21-25. There is also a file FishTycoon0.ldw, which contains settings.
Move those savegame files to the correct folder for your version of the game.
Launch Fish Tycoon and you should see your game in progress again.