Geburtshilfe für die Meerforelle

98 Tiere wurden in der Lippingau gefangen, um in einer Fischbrutanstalt für Nachwuchs zu sorgen. Die Jungfische werden im Frühjahr in die Bäche und Flüsse eingesetzt, aus denen die Elterntiere jetzt gefangen wurde

Der Silberstreit - Wir klären auf

Vor Kurzem sorgte die Landung einer riesigen Meerforelle in den sozialen Medien für rege Diskussionen – der Fang erfolgte in der Schonzeit, in der nur blanke Fische entnommen werden dürfen. Silber oder gefärbt? Wir haben einen Experten dazu befragt und nehmen das zum Anlass, mal über die Regelungen nachzudenke

Correlation analyses of Baltic Sea winter water mass formation and its impact on secondary and tertiary production

The thermal stratification of the upper water layers in the Baltic Sea varies seasonally in response to the annual cycle of solar heating and wind-induced mixing. In winter, the stratification down to the halocline is almost completely eroded by convection and strong wind mixing. Monthly averaged temperature profiles obtained from the ICES hydrographic database were used to study the long-term variability (1950 to 2005) of winter water mass formation in different deep basins of the Baltic Sea east of the island of Bornholm. Besides strong interannual variability of deep winter water temperatures, the last two decades show a positive trend (increase of 1-1.5°C). Correlations of winter surface temperatures to temperatures of the winter water body located directly above or within the top of the halocline were strongly positive until the autumn months. Such a close coupling allows sea surface temperatures in winter to be used to forecast the seasonal development of the thermal signature in deeper layers with a high degree of confidence. The most significant impact of winter sea surface temperatures on the thermal signature in this depth range can be assigned to February/March. Stronger solar heating during spring and summer results in thermal stratification of the water column leading to a complete decoupling of surface and deep winter water temperatures. Based on laboratory experiments, temperature-dependent relationships were utilised to analyse interannual variations of biological processes with special emphasis on the upper trophic levels (e.g., stage-specific developmental rates of zooplankton and survival rates of fish eggs)

Dem Leben der Meerforelle auf der Spur

Einzigartiges Forschungsprojekt an der Lippingau: Geomar-Wissenschaftler pflanzen Fischen Überwachungs-Chips ei

Egg buoyancy of flounder, Platichthys flesus , in the Baltic Sea—adaptation to salinity and implications for egg survival

Highlights: • Egg specific gravity vary between areas/subpopulations as an adaptation to salinity. • Egg diameter differ between areas/subpopulations whereas egg dry weight does not. • Habitat suitability for egg survival vary depending on salinity and oxygen conditions. • Egg survival probabilities increased following a major saline water inflow event. Abstract: Vertical distribution of eggs as determined by the egg buoyancy, i.e. the difference in specific gravity between the egg and the ambient water, have profound implications for the reproductive success and hence recruitment in fish. Here variability in egg specific gravity of flounder, Platichthys flesus, was studied along a salinity gradient and by comparing two reproductive strategies, spawning pelagic or demersal eggs. Egg characteristics of 209 egg batches (covering ICES subdivisions (SD) 22–29 in the brackish water Baltic Sea) was used to reveal the significance of egg diameter and egg dry weight for egg specific gravity (ESG), subpopulations, and egg survival probabilities of pelagic eggs following a major saline water inflow event. As an adaptation to salinity, ESG (at 7 °C) differed (p < 0.001) between areas; three subpopulations of flounder with pelagic eggs: 1.0152 ± 0.0021 (mean ± sd) g cm−3 in SD 22, 1.0116 ± 0.0013 g cm−3 in SD 24 and 25, and 1.0096 ± 0.0007 g cm−3 in SD 26 and 28, contrasting to flounder with demersal eggs, 1.0161 ± 0.0008 g cm−3. Egg diameter differed (p < 0.001) between subpopulations; from 1.08 ± 0.06 mm (SD 22) to 1.26 ± 0.06 mm (SD 26 and 28) for pelagic eggs and 1.02 ± 0.04 mm for demersal eggs, whereas egg dry weight was similar; 37.9 ± 5.0 μg (SD 22) and 37.2 ± 3.9 μg (SD 28) for pelagic, and 36.5 ± 6.5 μg for demersal eggs. Both egg diameter and egg dry weight were identified as explanatory variables, explaining 87% of the variation in ESG. ESG changed during ontogeny; a slight decrease initially but an increase prior to hatching. Egg survival probabilities judged by combining ESG and hydrographic data suggested higher egg survival in SD 25 (26 vs 100%) and SD 26 (32 vs 99%) but not in SD 28 (0 and 3%) after the inflow event, i.e. highly fluctuating habitat suitability. The results confirm the significance of ESG for egg survival and show that variability in ESG as and adaptation to salinity is determined mainly by water content manifested as differences in egg diameter; increase in diameter with decreasing salinity for pelagic eggs, and decreased diameter resulting in demersal eggs