Zusammenhang zwischen Schadstoffen aus der Elbe und missgebildeten Fischembryonen in der Deutschen Bucht.

The trends of malformation prevalence in embryos of dab, Limanda limanda, in the southern North Sea after the year 1990 mirrored the drop in major pollutants in the rivers draining into the German Bight. Despite this general decline we detected a pollution event in the southern North Sea in winter 1995/1996 employing the prevalence of malformations in dab embryos as an indicator. An abrupt rise in malformation prevalence in the embryos of dab, corresponded to a dramatic increase in DDT levels in parent fish from the same area, indicating a hitherto unnoticed introduction of considerable quantities of DDT into the system. This input could be traced back to discharges of unknown origen into the River Elbe.

Fang, Anlandungen, Discard und Bestand der Nordsee-garnele (Crangon crangon L.)

Landings of brown shrimp (Crangon crangon) for human consumption are not the only part that is taken from the North Sea shrimp stocks. Small amounts of industrial shrimps taken in the second half of a year in Germany add as well to the total amount that is taken from the stocks as the moribund animals discarded all over the year during the first sieving process on board, as the cooked and discarded ones in the second sieving on board and as those from the third sieving process ashore normally being crushed and used for animal feed stuff. All these fractions of the total catch of brown shrimps give a total of approximately 74 000 tonnes that were taken from the North Sea in 2005. Nevertheless, due to low predator abundance and changing climate conditions Crangon stocks show no signs of overexploitation so far with increasing LPUE values in the north-eastern part of the German Bight and decreasing ones in the south-east and Channel. There is the need of further investigations of these changes in the life history and distribution of shrimp as well as in the fishing behaviour and effort of the shrimp fleets .

Der PAH-Metabolit 1-Hydroxypyren in der Galle von Klieschen (Limanda limanda) aus Nord- und Ostsee

Due to their carcinogenic properties, polycyclic aromatic hydrocarbons (PAH) are important environmental contaminants which may lead to increased levels of neoplastic aberrations in fish liver. To measure the PAH contamination of fish, concentrations of PAH metabolites were determined in the bile. The main metabolite 1-hydroxypyrene was determined in concentrations from < 0.8 to 189 ng/ml in bile of dab caught in the North Sea and the Baltic Sea re-spectively. The concentrations are comparable to levels of 1-hydroxypyrene measured in cod and herring from the Baltic Sea. The highest concentrations in dab bile were measured in fish from the inner German Bight and the Kiel Bight.

Untersuchungen zu biologischen Schadstoffeffekten bei Nordseefischen: Langzeitdaten zum Auftreten von Lebertumoren bei der Kliesche (Limanda limanda)

Data are presented on the spatial distribution and long-term temporal trends in the occurrence of neoplastic liver lesions of North Sea dab (Limanda limanda) in the period 1988 to 2001, obtained in the framework of the regular fish disease monitoring programme carried out by the German Federal Research Centre for Fishery. Highest prevalences consistently recorded in the first part of the period occurred in the German Bight, at the Dogger Bank and at sampling sites off Humber and Wash. In contrast, stations in the northern North Sea (e.g. in the Firth of Forth area) were always characterised by low prevalences. Particularly during the first years of observation, a clear and general decrease in prevalence could be observed, that was most pronounced in the hot spot areas German Bight and Dogger Bank compared to the Firth of Forth. Current data reveal that, due to the decrease, spatial differences between sampling sites are now much less obvious than at the beginning of the studies. Limited chemical data available suggest that the temporal decrease in prevalence of liver tumours and their precursor stages generally correspond with the decrease in organic contaminants in dab livers as well as in water and sediments. However, the spatial variation in prevalence recorded can not entirely be explained by contaminant levels. For instance, the prevalence was continuously low in the Firth of Forth area wheras the contaminant levels in dab were comparatively high. The opposite feature was observed at the Dogger Bank. Future studies will therefore address the role of other host- and site-specific factors potentially involved in the aetiology of the disease.

Schadstoffüberwachung in Meeresfischen

For assessing the status of the marine environment of the North Sea and the Baltic Sea, international monitoring programmes are performed in the framework of the international conventions for the protection of the marine environment of the North Atlantic Ocean and the Baltic Sea. The German contribution to these programmes is covered by the national Joint Marine Monitoring Programme, which is carried out by several institutes of the coastal Federal States and the Federal Government of Germany. The Institute for Fishery Ecology of the Federal Fisheries Research Centre is responsible for the investigations of harmful substances in fish samples from the open sea areas. This article gives a short description of how this task is performed and, as an example, how concentrations of polychlorinated biphenyls and mercury in plaice from the German Bight have developed over a period of thirteen and eight years, respectively.

Zur Bedeutung des Größenunterschieds weiblicher und männlicher Nordseegarnelen für die kommerzielle Garnelenfischerei

Aiming at a better knowledge on the distribution and fecundity of hibernating Crangon crangon (L.), the R.V. "Solea" in January is sampling shrimps in the German Bight since 1991. A total of 3.000 shrimps (1.608 females and 1.392 males) have been investigated with regard to total length, to the width of the carapace and to spawning activity.

Kabeljau-Discards in der Deutschen Bucht

The German trawlfishery on cod in the German Bight causes discards. Their amount since 1983 has been estimated. The losses of millions of fish finally is the reason for losses of thousands of tonnes of valuable landings. The fishermen therefore should improve the selection rate of their nets.

Experimente über die Wirkung von UV-B auf pelagische Fischembryonen in einem Sonnenscheinsimulator

One of the supposed effects of the observed ozone depletion is the increase of solar UV-B irradiation at the seasurface. This will cause an impact on certain compartments of marine ecosystems. Especially, sensitive developmental stages of pelagic fish embryos might be affected. Embryos of dab (Limanda limanda) and plaice (Pleuronectes plalessa) were experimentally exposed 10 different amounts of UVB irradiation in a sunshine simulator. This programmable device allows the dosage of realistic solar irradiation in quality and guantity. Experiments were carried out in March 1995 and February 1996. Either artificially inserninated and reared emhryos of dab and plaice or embryos caught in the German Bight were exposed to simulated solar irradiation. The 1995 experiments served to identify the effective irradiation dosages. For the 1996 experiments irradiation applied was much lower, being dose to realistic valucs expected over the North Sea as a consequence of ozone depletion. The following end points were studied: 1. Mortality, 2. sublethal morphological effects (malformations), 3. DNA damage, 4. changes in buoyancy of embryos measured as changes in osmolarity of the perivitelline fluid. Conditions for the simulation of daylight were a c1oudless sky with a solar zenith distance of 34 % (air mass 1.2). The adopted ozone depletion was 40 % corresponding to 180 DU (Dobson Units) instead of 300 DU. In the 1995 experiments time and dosage dependent influenccs on mortality and buoyancy of embryos of dab and plaice were found. Even in those embryos which were protected from the UV-B spectral range a loss of buoyancy was registered after 12 hours in the simulator. No diffcrences in DNA integrity as determined by DNA unwinding of exposed and control embryos were found. Also with lower amounts of irradiation in the 1996 experiments dosage dependent acute mortality, malformations, and impact on the buoyancy of the emhryos was registered. Sublethal effects occurred as well in embryos protected against UV-B in the exposure chambers, but were not found in the dark controls. The impact of low dosages of UV-B on the buoyancy of pelagic fish embryos might indicate an important ecological threat and deserves further studies.

Neue Chance für Scholle und Kabeljau in der Nordsee

Two surveys in the German Bight revealed a relatively good recruitment for plaice and cod. However, with the current high effort and uneconomic way of fishing, most of these fish will end as discards. To protect young plaice during the winter months an increase of the mesh opening in beam trawls within the plaice box is suggested. Therefore, the fishermen are called upon to make a more considerated selection of their nets.