It stands for «big old fat female fish,» a portion of a fish population that has to be treated with great respect if you want to maintain a usable resource. (dotearth.blogs.nytimes.com)
For example, you are an average looking female fish, you should try to contact with an average looking male fish. (afreedating.com)
In ponds dominated by female fish, the researchers observed more pronounced ecological changes, including fewer zooplankton and a greater abundance of algae, than in male dominated ponds. (sciencedaily.com)