Sources : Eracliodes

Pliny the Elder [1st century CE] (Natural History, Book 9, 83): In the neighborhood of Heraclea and Cromna and in many parts of the Black Sea there is one kind that frequents the water at the edge of rivers and makes itself caverns in the ground and lives in these, and also in the shore of tidal rivers when left dry by the tide; and consequently they are only dug up when the movement of their bodies shows that they are alive. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Fish 7.38): Eracliodes are fishes that live about the Heraclia Pontus [city in Turkey], as Theophrastus writes. This species is found in the waters at the edge of rivers and digs in the lands which lie in the middle between the rivers. And this is a wonder, that it takes so much labor to change the direction of the water. It also makes caves for itself in the earth, so that it lives there even by retreating streams. - [Badke translation/paraphrase]