Diurnal and semi lunar feeding rhythms of the common goby Pomatoschistus microps in the brackish tidal marsh 'Het verdronken land van Saeftinge [sic]' (Westerschelde, SW Netherlands)
Bulayi, M.E. (1997). Diurnal and semi lunar feeding rhythms of the common goby Pomatoschistus microps in the brackish tidal marsh 'Het verdronken land van Saeftinge [sic]' (Westerschelde, SW Netherlands). MSc Thesis. RUG: Gent. 38 pp.
The influence of tidal, neap, spring and day night cycles on the feeding behaviour of the common goby Pomatoschistus microps was investigated in a creek of a salt marsh in the brackish zone of the Westerschelde estuary. Effects of tidal cycles were assessed using samples taken on 16, 17 and 19 August 1994 and the data of Thi (1995) which were collected on 7,8, 10 and 13 August 1994. A stow net with a length of 5 metres and a 1*1 mm mesh size was used for collecting the samples. Sampling was conducted over several tidal phases. On each occasion sampling started when water began to flood the creek. After slack water the net was turned around to sample the ebb current. The net was hauled every one hour. It was observed that most of Pomatoschistus microps entered the creek during the first hour of the tidal cycle and left the creek during the last two hours of ebb. The length frequency distribution ranged from 8-36mm standard length and with a modal length group ranged from 13-17mm standard length. Feeding activity of Pomatoschistus microps was highly influenced by tidal stimuli (tidal cycle and neap-spring tides). The fullness index showed a significant difference between flood and ebb: it increased with flood and decreased with ebb. Maximal fullness indices were observed between the last hour of flood (F3) and the first hour of ebb (E4). There was no significant difference between the feeding activity of fish caught during day time and at night. Neap and spring tides had an influence on the feeding pattern of fish, such that the fulness index increased with spring tide, reaching a maximum during the highest water levels. Pomatoschistus microps is a carnivorous species with a wide ranging food spectrum. The amphipod Corophium volutator was the most important prey. This amphipod had a high contribution to the diet both in terms of numbers and biomass. The mysid Mesopodopsis slabberi was also important. Neomysis integer, Nereis diversicolor and Crangon crangon were taken infrequently but due to their high biomass, contributed significantly to the total diet. Calanoid copepods were eaten very frequently but were unimportant in terms of biomass. The feeding habits are important to understand the role of animals in the trophodynamics of an ecosystem. Pomatoschistus microps takes a central place in the food web of the marsh system and the estuary.
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