What's the best open Database to query aquatic species traits? Or more simple, I'm searching for a database where I can query whether a species occurs in freshwater or marine environments.
FishBase is an excellent resource: http://www.fishbase.org/search.php
with many mirrors worldwide.
There is also an EXCELLENT package for R to query the database for just this kind of thing. It is by rOpenSci, and called rfishbase: https://github.com/ropensci/rfishbase
You can use the "Biodiversity" tag to look for crossover in marine and freshwater ecosystems . It will return a table that you could export if you're not actually an R user.
Thank you for your answers! Indeed I use R a lot and I prefer to query my data directly from R. Thanks for the rfishbase hint! Currently my work focuses on invertebrate organisms and I use the freshwaterecology.info data to check for freshwater organisms. Unfortunately they don't have a R API.