Tidal and diurnal influence on feeding behaviour of the common goby (Pomatoschistus microps) in an intertidal marsh creek of the Westerschelde
Van Thi, D. (1995). Tidal and diurnal influence on feeding behaviour of the common goby (Pomatoschistus microps) in an intertidal marsh creek of the Westerschelde. MSc Thesis. VUB: Brussel. 38 pp.
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Document type: Dissertation
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| Abstract |
In order to reveal whether the tidal, dark-light and/or semi-lunar cycles influence the feeding behaviour of the common goby Pomatoschistus microps, an investigation was carried out in a creek of a tidal marsh in the brackish zone of the Westerschelde estuary. A fyke net with the length of 5 m and 1*1 mm mesh size was used. Sampling was conducted on several tidal cycles. Sampling started when water began to flood the creek. After slack water, the net was turned around to sample the ebb current until all the water had left the creek again. The net was hauled every hour. The migration of the fish into and out of the creek was probably active. Most fish entered the creek during the first hour of the tidal cycles and left the creek during the two last hours of the tidal cycles. The density ranged from 3.2 ind.m-3 to 8 ind.m-3 and biomass ranged from 32 mg AFDW .m-3 to 52 mg AFDW .m-3 in the four tidal cycles considered. The length-frequency distribution ranged from 7 mm to 41 mm, and the dominant length group ranged from 10 to 20 mm SL (81 %-92%). The fullness index (FI) increased with floodtide and decreased with ebbtide. The FI of daytime and nighttime did not differ significantly. This suggests that the day-night cycle is not important in the feeding pattern of Pomatoschistus microps. At the second hour (F2) on springtide the FI showed a clear peak (August 10) as compared to the other tidal cycles (August 7 and 13). During springtide, the increase in FI with flood was faster than on the other tidal cycles. Pomatoschistus microps is a predaceous species with a wide food spectrum. Numerically, the amphipod Corophium volutator was the main prey in the stomachs during ebbtide, except on tide of 10th when they mainly fed on insect larvae. During the floodtide, copepods and mysid Mesopodopsis slabberi were also important prey items. Gravimetrical term, Neomysis integer, C. volutator and M. slabberi contributed most part to the biomass of the diet. |
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