In an earlier posting I said that I was confused by the identity of peixe espada. Thanks to Wikipedia I have solved it. Peixe espada seems like it would mean "fish sword" though being a thin long silvery fish with big eyes it did not look anything like a "swordfish" which is espadarte in Portuguese. It is definitely not a scabbard fish which looks very different again.
It occured to me that Wikipedia can be run in Portuguese and I found an article by doing a search using the Portuguese fish name. While I do not understand the article it yields the zoological name trichiurus lepturus. Putting this name into Wikipedia in English leads to a further article on the largehead hairtail or Atlantic cutlassfish. The first name does not even sound like a fish to me so I will use the latter!
I have often found language dictionaries unreliable for biological terms while Latin names are universal.