Surges of Winter Flounder, Pseudopleuronectes americanus, into the Intertidal Zone

Abstract

Movement of winter flounders, Pseudopleuronectes americanus (Walbaum), into the intertidal zone was observed by underwater television situated in a herding fence. Flounders enter the intertidal zone with the rising tide. Peak movement occurs 2–2.5 hr after low tide. Movement generally falls off 3.5 hr after tide begins to rise. Flounders occupy the area for 6–8 hr and then surge back to the sublittoral 2.5–0.5 hr before the next low tide. Small flounders move with the same synchrony as large flounders, but tend to make short movements up and down the beach, with net movement away from shore while tide is falling. Large flounders are more strictly directional. Movements of eight species that occurred with the flounder are compared. Because of the scale of the flounder movement, and because of published observations of pleuronectids feeding in the intertidal zone, it is proposed that the intertidal zone is a major feeding area for northern populations of winter flounder. Actions that interfere with productivity in the intertidal zone (oil pollution, tidal impoundments) are likely to reduce productivity of flounder populations.