Fish species diversity in Daya Bay has changed over time. A study analyzed data from 1980 to 2007 and found that the number of fish species decreased from 157 in the 1980s to 107 in 2004-2005. The types of dominant fish also shifted from high-value to low-value species. The study showed that fish stock density in the Bay decreased over the years, with a larger decline from 1990-2007 compared to 1980-1999. The abundance of fish in the Bay also had a larger seasonal fluctuation in the later period.