Effects of tidal movement on the feeding of winter flounder pseudopleuronectes americanus (Walbaum) in Long Pond, Newfoundland and Brandy Cove, New Brunswick

Wells, Barbara Ford (1974) Effects of tidal movement on the feeding of winter flounder pseudopleuronectes americanus (Walbaum) in Long Pond, Newfoundland and Brandy Cove, New Brunswick. Masters thesis, Memorial University of Newfoundland.

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Abstract

Tidal movements and feeding in winter flounder were found to be strongly correlated in Brandy Cove, N.B. during the summer feeding period of this species. Tidal amplitude at the study site was six to seven times larger than for other coastal areas. Stomachs of fish moving inshore were empty or contained only smal quantities of prey whereas stomachs of those leaving the intertidal zone were full with fresh, intertidal prey. Fish caught in the subtidal zone at high tide fed as much as those in the intertidal zone but fed on subtidal and intertidal prey in contrast to intertidal feeders which fed, generally, only in that zone. Prey consumed support the classification of these fish as polychaete-mollusc-crustacean feeders. -- Winter flounder studied in Long Pond, Newfoundland displayed tidal movement across the bottom of the shallow subtidal zone and into the narrower intertidal zone. They ate considerably less than those in deeper water in Conception Bay. The poor feeding on the shallow ground in Long Pond was due to a poor standing crop and diversity of benthos. It is concluded that the shallow water feeding is controlled by three interacting parameters, which in order of importance are: temperature, tides, and surf conditions. Food taken by shallow water fish corresponded with the benthos known to occur there and differed from that taken by fish from the bay. Constancy of diet among fish on the shallows showed little exchange with fish from the deeper ground on either a daily or monthly basis. An apparent relationship between tidal movement and feeding in Long Pond was found and over a 12 hr cycle was similar to tidal feeding observed in some North Sea flatfishes. -- Peak consumption of 2% body weight per tidal cycle was the same in both areas (New Brunswick, Newfoundland) and indicated that P. americanus was a moderate consumer of energy in contrast to some European flatfishes which consume 4-5% of body weight. -- Movement in Brandy Cove and Long Pond is considered to be a feeding migration. While feeding in the pond was less significant than that in Brandy Cove, postlarvae, immature and adult winter flounders were consistently seen in the intertidal zone of the pond. -- In areas of large tidal range, gradually sloping beaches and coarse to fine sediments, the intertidal zone may serve as an important feeding ground and should be protected from human disturbance in order to maintain or improve our flatfish stocks.

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