I Got Games has gained 15 million registered users in the last four years through porting Chinese massive multiplayer online games to the rest of the world — its audience loosely parallels Facebook’s, with a third of its users in North America, a third in Europe, and the rest in Latin American and Southeast Asia. And now, having already successfully launched original MMOs, it’s starting to make social games.

The company will launch a new Facebook app this coming weekend called FishIsle. The game will combine the virtual aquarium-caring features of games like Happy Aquarium and My Fishbowl with the more goal-oriented structure of virtual farming games like FarmVille, says Mark Zhang, vice president of operations at IGG’s local office in Santa Clara, Calif.

In the game, players travel across a virtual ocean in fishing boats, nurturing virtual aquatic farms of salmon, flounder, shrimp, jelly fish and other types of underwater life, harvesting each when they’re read. Players can also purchase different types of fishing boats, and decorate their own islands with buildings and other features. The interface shows the game from a 45-degree, birds-eye angle, to add to the feeling of being in an alternate virtual world. The company also plans to roll out more MMO-style features.

The virtual store and some other parts of the interface, in the finest of social gaming tradition, look quite similar to other hits (like FarmVille).

As IGG has done with its MMOs, and as other social games are doing on Facebook, FishIsle will be free to play, and will make money from selling virtual goods.

IGG has twelve studios in China, although it is based on the Cayman Islands, and also plans to roll out 18 more traditional MMOs. FishIsle is its initial move into social gaming, as the company has 7 more social titles planned — also, it built this game in 3 months, Zhang tells us, so expect these other games pretty soon.

To get this first game off the ground, so to speak, the company also plans to cross-promote it within some of its existing MMOs, on its home site and within partner MMO games in the US. Eventually, the company may also look at buying Facebook ads to promote games. It already has 14 successful MMOs, and says it is bringing in “multiple millions” in revenue, with 85% of the money coming from North America and the United Kingdom.

It has raised two rounds of funding totaling $15 million from IDG, Hearst Interactive, and Vertex Venture Holdings (a venture arm of the Singapore government).

[Screenshots via Blend Games]