Information on possible effects of pollution on fish life is reviewed with special emphasis to the North Sea.Concentrations of heavy metals are high in onshore waters, sediments and organisms. Offshore regions are considered to be not endan ered. In estuaries concentrations of certain heav metals are often surpassing thresholds, which have %een experimentall demonstrated to produce subLthal effects on marine organisms. Also mussel culture areas had to be cLsed due to excess of cadmium contamination. Mercury in fillets of cod in the southern North Sea sometimes reaches 0.3 ppm representing ! 4 of the legal limit. Reductions of inputs are necessary due to the bioaccumulative and toxic potential of heavy metals.Organocblonne contamrnation of water, sediments and organisms is higher in the southern than in the northern North Sea. In offshore areas clearly elevated levels of PCB's, which are the dominating organochlorine compound in marine or anisms, have been analyzed. At present only a minor fraction of total organochlorine residues accumufa7ed in marine biota is analyzed. Margins between experimentally derived lethal levels and those occurring in marine biota are narrow suggesting that sublethal effects mi ht occur. One of the special concerns in the context of organochlorine contamination has to be seen in k e potential of these substances affectin the re roductive capaci of marine organisms. Reduction measures are urgently necessary and shoulcfinclu8e substances withTioaccumulative and toxicological potential, which are not presently included in Marine Monitoring Programmes.Impact of otl pollution is considered to be a regional problem, although especially in estuaries concentrations in the water column might be hi h Input through oil platforms has led to local reductions in benthic communities. Measures have to%etaken, to further reduce these inputs also in view to avoid contamination of fish in the vicinity of oil fields.Oxygen depletron in German and Danish coastal waters has been shown to be a severe degradation in coastal water quality resulting in significant impact on fish PO ulations. Indications for large-scale avoidance reactions of low DO-areas and mortalities of fish and fenthos or anisms have been demonstrated. It is suspected that the low DO-situations are related to increasej nutrients input and high ph toplankton production. Improvement of the situation can only be expected, if input of nutrienrs is redruced.Reasons for the occurrence of toxic plankton blooms are not understood. An intensified research is necessary, to avoid damage to fisheries and mariculture.Although activity of radionucleids in North Sea waters is increased due to input of radioactive material from La Hague and Sellafield reprocessing units, the present levels of activity are not considered to be a threat for marine life.The same holds for thennal pollution, which is, depending on the recipient area, expected to have only local effects.Sewage sludge dumping and discharge of untreated sewage introduce significant amounts of acco...

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Zusammenfassung Über zwei Versuchsreihen mit Netzkäfighaltung und ‐fütterung an Forellensetzlingen in Süß‐ bzw. Ostseeküstenwasser wird berichtet. Der Einfluß folgender Faktoren in Alleinfutterrezepturen auf Gewichtszunahme und Futterverwertung der Forelle wurde geprüft: 1. Proteinkonzentration (32 bis 49 %), 2. Austausch tierischer (Fischmehl) gegen pflanzliche Eiweißträger (Methionin‐ und Lysin‐ergänztes Sojaschrot), 3. partielle Energiebedarfsdeckung durch native bzw. walzengetrocknete, also hitze‐aufgeschlossene Quellstärke (aus Mais), 4. der summarische Effekt einer Vollvitaminierung. Die tägliche Futterzuteilung mit 2 % des KGW erfolgte restriktiv. Der Versuch I/70 mußte nach 123 Fütterungstagen wegen Fremdwassereinbruchs abgebrochen werden. Für Versuch II/71 liegen Ergebnisse nach 76 Fütterungstagen vor. Walzengetrocknete Quellstärke wird im Vergleich zum nativen Stärkekorn energetisch günstig verwertet. Der teilweise Ersatz tierischer Proteine durch pflanzliche Eiweißträger bei ausreichender Aminosäurensupplementierung und hinreichendem Angebot verfügbarcr Kohlenhydrate erscheint möglich. Weitere Untersuchungen bezüglich des Eiweißaustausches sind jedoch erforderlich. Die derzeitigen futtermittelrechtlichen Normen zur Herstellung von Forellenmischfutter (Rohprotein mindestens 35 % und mindestens 35 % tierische Eiweißfuttermittel in der Ration) sind möglicherweise qualitativ zu niedrig angesetzt. Für Forellenmischfutter in der Teichwirtschaft sollte ein Rohpretein‐gehalt von 40 %, vornehmlich resultierend aus hochwertigen Fischmehlen, vorläufig nicht unterschritten werden. In die Restrezeptur können aufgeschlossen Stärketräger (Quellstärke) vermehrt Eingang finden.

After a period of stabilization lasting more than 20 years, the Thai sea fisheries developed rapidly during the past decade through the introduction of trawl fishing. Suitable nets and fishing techniques were demonstrated and introduced in the course of a German bilateral aid project. This new input, together with a high level of technical abilities among the fishermen, the availability of sufficient capital to finance a trawler fleet of more than 2,500 boats, and adequate support from the Thai Government, resulted in rapid development of trawling from small vessels. Landings were about 600,000 metric tons of groundfish from the coastal area in 1970. About half of this is for human consumption, the remainder mostly being used fresh for duck food or, after processing, as chicken food. The level of development achieved has unfortunately meant that the moderately rich bottom-fish resources of the Gulf of Thailand have become overexploited. In 1971 the catch per unit of effort had decreased to only a quarter of the original, making trawling operations only marginally economic. This points up the difficult problem of the control of fishing effort, which the Government of Thailand, no less than other nations, has not yet been able to resolve satisfactorily.

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