Wiktionary(0.00 / 0 votes)Rate this definition: upthrust(Noun) an upward thrust. upthrust(Noun) buoyancy. upthrust(Noun) an upward movement of part of the Earth's crust. upthrust(Verb) to thrust something upwards.
Predators, Food and Feeding: Natural predators of winter flounder include sharks, oyster toadfish, summer flounder, striped bass, monkfish and spiny dogfish. When feeding, a winter flounder will lie motionless, partly concealed on the bottom, with its head raised off the bottom, braced by the dorsal fin.
Like other fish, flounders hatch with one eye on each side of the head. Movement of the right eye to the left side of the head begins when the fish is 1/3 to 1/2 inch long and is complete when the fish is 3/4 inch to 1 inch long. At this same time, the left side develops its dark color and the right side turns white. After hatching, southern flounder larvae eat microscopic floating animals (plankton). As juvenile fish, they eat small bottom animals. At about 6 inches long, they adopt their adult diet of fish and shrimp.