Sources : Trebius

Pliny the Elder [1st century CE] (Natural History, Book 9, 41; 9, 42): [Book 9, 41] Trebius Niger says that it [the murex, sea-snail] is a foot long and four inches wide, and hinders ships, and moreover that when preserved in salt it has the power of drawing out gold that has fallen into the deepest wells when it is brought near them. [Book 9, 42] The maena changes its white color and becomes blacker in summer. The lamprey also changes color, being white all the rest of the time but variegated in spring. Also it is the only fish that lays its eggs in a nest, which it builds of seaweed. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Fish 7.85): [Thomas misread the Pliny passages included above to "create" the trebius. See the explanation under General Attributes on the main beast page.] Trebius is a black fish, as Pliny says; it is a foot in length, and though it is so small this fish is five inches thick. Pliny says that it possesses this power, that if a part of it preserved in salt, it can draw up gold that has fallen into the deepest wells when it is brought near. It changes color to white in winter and becomes blacker in summer. Of all the fishes, the trebius is the only one that makes its nest out of seaweed and lays its eggs in the nest. Trebius is in the ocean, and pierces ships with its hard beak, and it is the greatest of those in the ocean. - [Badke translation/paraphrase]