Cattrijsse, A.

Hampel, H.

Open Marine Archive

Tidal, die1 and lunar changes in estuarine marsh nekton 
Hampel H.' and A. Cattriisse2 
' Ghent University, Biology Department, Marine Biology Section 
K.L. Ledeganckstraat 35, B-9000 Gent 
E-mail: hampelh@hotmail.com; henrietta.hampel@rug.ac.be 
I Flanders Marine Institute 
Victorialaan 3, 8-8400 Oostende 
The utilisation of a brackish estuarine marsh by nekton was investigated over a lunar cycle in August 
1994. The nekton migrating in and out of the intertidal creeks of the marsh 'Het Verdronken Land van 
Saeftinghe' in the Westerschelde estuary, SW Netherlands, was sampled passively during seven complete 
tidal cycles. Sampling one tidal cycle yielded three consecutive flood samples and four consecutive ebb 
samples. Sampling occasions, occurring every two to three days, covering all die1 and lunar situations 
allowed comparing tidal, die1 and lunar influences on the composition of the intertidal nekton fauna. 
Two different tidal migration modes were observed. The mysid shrimp Mesopodopsis slabberi showed 
i maximum abundance around high tide. For the remaining common nekton species: the mysid Neomysis integer, the shrimps Palaemonetes varians, the amphipod Corophium volutator, the crab Carcinus 
maenas and the goby Pomatoschistus microps, highest densities were recorded during lower water 
heights. The fauna assemblage shifts clearly between the different tidal stages. The total amount of 
detritus was found to be the most important parameter structuring the assemblages. 
O n  two occasions consecutive day and night.s~rnples were taken. Total densities were clearly higher 
during night samples. During full moon a clear difference in community composition was noticed 
between the night and the day samples. During neap tide, differences between day and night were less 
clear. 
No  clear correlation was found between water height and total nekton densities. Except for the two most 
abundant species Mesopodopsis slabberi and Neomysis integer of which recorded averages were higher 
during spring tide and lower during neap tide. A clear shift in community composition was observed 
between the spring tide and the neap tide with water height as the main environmental factor. 


Tidal, diel and lunar changes in estuarine marsh nekton

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