fish migration route page with map (http://www.minvenw.nl/rws/riza/home/publicaties/nieuwsbrieven/migratie_forel/engels/nieuwsbrief_4/trekroutes_nieuwsbrief_4)
data (http://www.binnenvaart.be/htm/02ws/technisch/22fichemaasmond.htm)
... tropical[?], with little seasonal variation, though the subtropical south is more temperate and can occasionally experience frost and snow. Precipitation is ...