Fischarten der westlichen Ostsee – Untersuchungen von 2000 bis 2002

Ichthyoplankton provides information on the species com-position in an area of investigation and leads to a better understanding of the entire fish community. Every year since 1993 May/June (from 2000 in April/May) an ichthyoplankton survey in ICES Subdivision 22 and 24 has been done to sample the plankton community in the western Baltic Sea. One objective was to acquire indicators of possible changes in the natural structures of the fish com-munity. The time series derived from the Bongo-Net samples is too short to show a trend in larval densities. Up to now samples in the western Baltic Sea yielded only low mean densities. According to the reproductive biology the fish species were divided in three major groups: •Fish species with a long developmental phase in the plankton community •Small short lived species with benthic eggs and a reduced planktonic phase •Guests without local spawning populations. Species were identified, which were absent in the plankton of the western Baltic Sea in the 1960s and 1970s.

Der Fischei-Test: Ein Toxizitätstest für ökotoxikologische Untersuchungen

Zebrafish (Danio rerio) embryos have been used to quantify the teratogenic potential of environmental samples and harmful substances respectively. The short spawning interval renders this species a good test organism in toxicological research. Due to the transparency of the eggs several lethal and non-lethal endpoints can be detected in parallel after 48 h of embryonic development. Zebrafishembryos have been shown to be sensitive to a number of environmental relevant contaminants, as well as to ex-tracts from polluted sediments

Veränderungen sensorischer und instrumenteller Parameter während der Gefrierlagerung von Ostseedorsch (Gadus morhua) bei unterschiedlichen Temperaturen

Changes in sensory and instrumental quality parameter sand in thawing drip, cooking drip and total drip loss of frozen stored Baltic cod fillets (Gadus morhua) at different storage temperatures were investigated. Cod fillets stored at –20 °C and –30 °C exhibited the lowest drip losses and obtained the highest sensory scores. Drip losses were found to be highest in cod fillets stored at –10°C and in double frozen fillets stored at –20 °C. These two experiments also gave the lowest sensory scores. The texture parameters increased during storage parallel with storage time. The waterbinding capacity was lowest at –10 °C and almost constant at –30 °C. There is a good correlation between the sensory scores for “tough” and the instrumental texture measurement for hardness and chewiness.

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.

Eu-Projekt zur Seebeprobung von Schleppnetzfangen in der Nordsee erfolgreich abgeschlossen

Six countries around the North Sea have contributed to an EU-funded project collecting information about the catch composition in commercial fisheries. The aim was, by including that part of the catch, which is discarded after sorting, to gain better knowledge about the real stock size of the most important fish species. Additionally, the data shall contribute to a better understanding of the ecological effects of trawling.

Aktuelle Planungen zur Regelung der Beifangproblematik in der Krabbenfischerei

At present the fishery for the brown shrimp (Crangon crangon L.) is one of the most economically rewarding fisheries in Europe. Due to the small size of the target objects this fishery has to be carried out with rather small meshes. As it is, however, performed on the nursing grounds of important fish species it encounters a severe bycatch problem. On this basis, EU Council regulation 850/98 demands the use of either sieve nets or sorting grids from 1 July, and to pass pertaining national bye-laws. Germany discusses to use either sieve nets of 70 mm mesh opening or sorting grids of 20 mm bar distance, and tries to achieve a harmonization of the byelaw with neighbouring countries of The Netherlands and Denmark to ensure equal conditions on the same fishing grounds.

Ein Modell der mathematischen Optimierung zur Bestimmung der optimalen Größe und Struktur der deutschen Fischereiflotte unter stochastischen Bedingungen

A mathematical model to optimize the German fishing fleet is draftet and it’s data basis is described. The model has been developed by Brodersen, Campbell and Hanf in 1994 to 1998. It could be shown, that this model is flexible enough to be applied successfully to a lot of very different political questions, if adapted accordingly. The economic consequences of measures of fishery politics, the effects of technical advances, but also increasing incertainties can, to some degree, appropriately be assessed quantitatively. Finally it could be shown that, principally, the available account of data is a good basis for investigations into fishery economics and fishery politics. However there is a need to treat the source of data continuously and competently in order to make these informations available quickly. Statistical data to reflect the fishery sector are valuable. However, they obtain their full value only when judged by experts from the fishing industry, biology and technical fishery research.

Spezifizierungsanalyse des Quecksilbers - ein möglicher Beitrag zur Erforschung der Auswirkungen klimatischer Veränderungen auf die belebte Meeresumwelt

The predominantly occurring chemical forms (species) of mercury (Hg) that occur in the environment are elemental mercury (Hg0), divalent inorganic mercury (Hg2+) and dimethylmercury (CH3HgCH3) and monomethylmercury(CH+3Hg), the latter of which is strongly accumulated by marine organisms. Conversions between the different mercury species provide the basis of the complex distribution pattern of mercury on local, regional, and global scales. An analytical system using hyphenated instrumental techniques has been developed and validated in order to determine inorganic and organic mercury species in marine biota (fish and plankton). It is suggested than mercury species analysis can provide a useful tool to investigate the effects of climate changes on the bio-transformation activity of certain marine microorganisms.

Fischereilich-ökonomische Überlegungen zu Chancen und Risiken in der Garnelenfischerei - am Beispiel des Schollendiscards (Ein Thesenpapier auf der Basis von EU-Studien und Langzeitreihen)

Though economic research is not one of the tasks of the German Federal Research Centre for Fisheries, basic in-formation for such work is available from biologic studies on fish biomass, discards and seasonal abundance of species. Results from EU-studies on brown shrimp fisheries show the effect of discarding juvenile fish, especially plaice, the possibly lost numbers and value of this fish as well as chances of reducing these losses by a timely effort reduction in summer and the use of selective nets throughout most parts of the year. However, it is also made clear, that these costly measures may have no effect on the stocks due to biological compensatory effects observed in strong year classes of plaice e. g. 1996, with high landings and collapsing prices. Therefore sound biological and economic data and methods are needed to assess the economic effects of management measures on fishermen’s situation and markets. Compensations for catch limitations may become inevitable.

Ökonomische Betrachtungen zu kurz- und langfristigen Maßnahmen in der Fischerei. Vorstellung von drei Forschungsprojekten

At present, there is practically no research on fisheries economics in Germany. Due to special interest of a research assistant in the field of land economics at the Institute of Botany of the University of Greifswald two projects on fisheries economics are being carried out, and a Ph. D. thesis on this topic has been finished. Basically two levels must be distinguished: business level and economics. Business economics relate mainly to operational and market analysis, but also to consequences of political measures for a single company. Economical considerations relate to long-term measures. It is important to find a compromise between short-term economical success and stable long-term conditions for the fishery.

Aktuelle Aspekte und Besonderheiten der deutschen Flunderfischerei in der Ostsee im Jahr 2002

Although the fishery on flounder in the German fishery zone in 2002 was characterised by good catch possibilities, a dramatic decrease of landings was observed because of marketing problems and low prices. Due to increasing international fishery pressure on flounder a quota system should be established in the future. The German flounder landings could be increased by a better marketing strategy to meet the optimal requirements for a reliable German quota. For 2003 the stock condition is expected to be good which could ensure a successful flounder fishery. It is necessary to stabilize the present technical measures for a better selection of the codend in the medium term.

Starker Nachwuchsjahrgang 2002 des Herings der westlichen Ostsee

Several fishery independent estimates of the year-class strength are necessary for the assessment and the management of the total fish stock. An index for the year-class strength of the spring spawning herring in the western Baltic Sea is estimated on the basis of larvae surveys in the most important spawning ground. The results indicate a strong year-class 2002.

Technische Empfehlungen für den künftigen Einsatz von Plattfischsteerten in der Ostsee

Die Grundschleppnetzfischerei in der Ostsee konzentriert sich im wesentlichen auf den Fang von Dorsch- und Plattfisch. Neben der Dorschfischerei gibt es auch beim Fang von Plattfisch gebiets- und zeitweise erhebliche Beifänge an untermaßigen Fischen, die verworfen werden müssen. Für beide in Form und Verhalten sehr unterschiedlichen Fischarten können bis dato die gleichen Steerte eingesetzt werden. Um die durch diese Mix-Fischerei an der südlichen Ostseeküste gegebenen Probleme zu verdeutlichen und auf eine zukünftig differenzierte Behandlung für die technischen Maßnahmen zur Verbesserung der Selektivität hinzuwirken, werden seit 1998 vergleichende Untersuchungen mit Schleppnetzsteerten unterschiedlicher Konstruktion durchgeführt.

WEFTA-Laborvergleichsuntersuchungen zur pH-Bestimmung in Fischerei-Erzeugnissen - Eine gemeinsame Aktion der Western European Fish Technologists' Association

12 samples (6 original samples and 6 diluted samples) were analysed by 14 WEFTA laboratories for their pH values in an inter-laboratory comparison exercise. As a result it can be stated that the majority of participating laboratories could determine the pH values very exactly. The pH values obtained are ranging only little around the calculated mean (less than 0.1 pH unit). It could also be demonstrated that the participating institutes could analyse both, pH values in fishery products and aqueous salt solutions. However, also in this exercise a number of outliers and deviating values have been detected. Therefore it is of utmost importance to calibrate the pH electrodes in regular intervals and to maintain them carefully. Intra-laboratory comparison measurements are recommended to detect weak points.