Historical clue formulations

• Omnivorous fish of the Amazon — 2025-07-01
• South American predator whose name translates to "tooth fish" — 2023-06-19
• Amazon predator — 2020-06-07
• Ruthless sort — 2013-03-08
• One in a dangerous school — 2011-03-26
• Ruthless type — 2008-06-28
• Literally, "fish tooth" — 2008-02-10
• Voracious fish — 2004-11-16
• Underwater menace — 2003-10-19
• Carnivorous fish — 2001-05-15
• It might bite the hand that feeds it — 1997-06-19
• One in a dangerous school — 1995-10-21