Peitsch, A. (1993). Difficulties in estimating mortility rates of Eurytemora affinis in the brackish water region of the Elbe estuary. Cahiers de Biologie Marine. 34(2):215-224, figs. 1-9, tab. 1.

98721

10.21411/CBM.A.2BA32C60 [view]

Peitsch, A.

1993

34(2):215-224, figs. 1-9, tab. 1.

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Mortality rates of the copepod Eurytemora affinis from the Elbe estuary were estimated. From April to September 1989 six samples were taken twice a week during the flood phase at an anchor station (km 695) in the oligohaline section of the Elbe estuary. Maxima of different instars were found at different times during the flood phase. The peaks of abundance were shifted from low to high water as the organisms grew older : it seems that the population would be slowly driven out of the estuary. To obtain a representative value of the population density for the calculation of mortality rates a weighted average of the abundance of each sampling day was used. With these data cohort analysis was carried out. Highest daily mortality rates occurred between naupliar stages V and VI. Mean mortality rates of nauplii were 0,15-0,26 d-1. For copopodids low daily mortality rates of 0,05 d-1 were estimated. Mortality in estuaries not only consists of predation and physiologically death. In addition the transport of animals from upstream and losses of animals to the downstream part of the estuary that the spatial separated maxima of different instats of Eurytemora affinis during a tidal phase affected the estimation of mortality rates.

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