Selective tidal stream transport of flounder larvae (Platichthys flesus L.) in the Dollard (Ems estuary)
Jager, Z. (1999). Selective tidal stream transport of flounder larvae (Platichthys flesus L.) in the Dollard (Ems estuary), in: Jager, Z. Floundering: processes of tidal transport and accumulation of larval flounder (Platichthys flesus L.) in the Ems-Dollard nursery. pp. 87-108
In: Jager, Z. (1999). Floundering: processes of tidal transport and accumulation of larval flounder (Platichthys flesus L.) in the Ems-Dollard nursery. PhD Thesis. Universiteit Amsterdam: Amsterdam. ISBN 90-9012525-6. 192 pp., more
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| Keywords |
Behaviour > Migrations > Vertical migrations
Cells > Sexual cells > Eggs
Chordata > Vertebrates > Fishes > Osteichthyes > Pleuronectiformes > Marine fishes > Flounder
Developmental stages > Larvae > Fish larvae
Fauna > Aquatic organisms > Aquatic animals > Fish
Fishes > Osteichthyes > Pleuronectiformes > Pleuronectidae > Pleuronectes > Plaice
Motion > Water motion > Water currents > Tidal currents
Nursery grounds
Transport
Water bodies > Coastal waters > Coastal landforms > Coastal inlets > Estuaries
ANE, Germany, Ems Estuary [Marine Regions]; ANE, Netherlands [Marine Regions]; ANE, Wadden Sea [Marine Regions]; Denmark, Wadden Sea; Netherlands, Wadden Sea
Marine/Coastal; Brackish water |
| Abstract |
The vertical distribution of flounder larvae (Platichthys flesus L.) was investigated in the Dollard (Ems estuary, Wadden Sea) in relation to tidal phase and physical variables in order to address the question whether larval migration into the nursery is accomplished by passive transport, or is influenced by active (swimming) behaviour. Larval concentrations were measured twice per hour simultaneously at three water depths from low water (LW), through high water (HW), to the next LW slack. Physical variables were measured at the same time.Maximum concentrations of flounder larvae were 433 m-3 in 1994 and 40 m-3 in 1995. There were tidal variations in larval concentrations in all three water layers and the vertical distribution varied as well. The highest larval concentrations were usually found near the surface during flood and the lowest in the midwater layer during the ebb. In contrast to larval concentrations, turbidity was always highest near the bottom. The observation that larval vertical distributions deviate from those of suspended matter and vary in a different way led to the rejection of an entirely passive transport mechanism.The vertical distribution of larvae during flood supported the selective tidal stream transport hypothesis, but the relatively high number of flounder larvae in the surface layer during ebb was in contradiction with it. The high surface concentrations during ebb may have been caused by different origins of the water layers and thus larvae, or by an inability of the metamorphosing larvae to resist the strong ebb currents. The data suggest that the transport process inside the nursery may favour retention. |
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