I do often consult scientific publications ("papers") to get the original facts - i.e. not a "second hand" quote of the facts. (It's surprising how regularly you come across the same "fact" that people rehash without checking the source.) However, I also frequent trusted web sites such as FishBase and ARKive. National Geographic is also good, but must be double checked because they occasionally make errors.
It is recommended to find two independent trusted sources for each fact you cite in your manuscript, wherever possible.
One last tip: as Vijaya says, note down your sources as you are writing. If you don't, it can sometimes be very difficult to track them down again when you need them (when you send your ms and bibliography to publishers). It can be slow at first, but is worth it in the end.
Best of luck!