摘要:

SummaryInformation on possible effects of pollution on fish life is reviewed with special emphasis to the North Sea.Concentrations ofheavy metalsare high in onshore waters, sediments and organisms. Offshore regions are considered to be not endangered. In estuaries concentrations of certain heavy metals are often surpassing thresholds, which have been experimentally demonstrated to produce sublethal effects on marine organisms. Also mussel culture areas had to be closed due to excess of cadmium contamination. Mercury in fillets of cod in the southern North Sea sometimes reaches 0.3 ppm representing 1/3 of the legal limit. Reductions of inputs are necessary due to the bioaccumulative and toxic potential of heavy metals.Organochlorine contaminationof 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 organisms, have been analyzed. At present only a minor fraction of total organochlorine residues accumulated in marine biota is analyzed. Margins between experimentally derived lethal levels and those occurring in marine biota are narrow suggesting that sublethal effects might occur. One of the special concerns in the context of organochlorine contamination has to be seen in the potential of these substances affecting the reproductive capacity of marine organisms. Reduction measures are urgently necessary and should include substances with bioaccumulative and toxicological potential, which are not presently included in Marine Monitoring Programmes.Impact ofoil pollutionis considered to be a regional problem, although especially in estuaries concentrations in the water column might be high. Input through oil platforms has led to local reductions in benthic communities. Measures have to be taken, to further reduce these inputs also in view to avoid contamination of fish in the vicinity of oil fields.Oxygen depletionin German and Danish coastal waters has been shown to be a severe degradation in coastal water quality resulting in significant impact on fish populations. Indications for large‐scale avoidance reactions of low DO‐areas and mortalities of fish and benthos organisms have been demonstrated. It is suspected that the low DO‐situations are related to increased nutrients input and high phytoplankton production. Improvement of the situation can only be expected, if input of nutrients is reduced.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 ofradionucleidsin 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 forthermal pollution, which is, depending on the recipient area, expected to have only local effects.Sewage sludgedumping and discharge of untreated sewage introduce significant amounts of accompanying heavy metals, which can be expected to have a negative influence on the total metal budget of recipient waters. Nutrient input through sewage will exhibit only local effects.Dumping of wastes fromtitanium dioxide industryare suspected to be causally linked to the occurrence of increased prevalences of certain diseases of dab in the German Bight. Present management strategies should take account of the fact that through dumping of waste from titanium dioxide production significant quantities of heavy metal are introduced into the southern North Sea.Also theincineration of chemical wastesat sea should be reduced due to uncertainties concerning quantities and toxicity of incineration products and their potential impact on marine life.It is concluded that clear evidence exists for pollution impact in estuarine regions. Most of the major estuaries at the North Sea coast show benthos reductions, which can be related to water quality and it has to be assumed that areas of a sublethal effect are located in the vicinity of those areas of well demonstrated effects. They are of unknown size and attempts have to be undertaken to quantify areas of sublethal impact.The occurrence of fish diseases is interpreted as an expression of degraded water quality. Some of the diseases detected can produce mortality, thereby having an as yet unquantified impact on fish populations. The presence of fish diseases also reduces the marketability of catches.It cannot be excluded that changes in species composition of fish populations in German Wadden Sea areas are related to pollution. Concentrations of organochlorine substances in fishes of the southern North Sea give rise to the concern that their reproductive capability might be impaired. Future work has to be directed to this problem. Impact of pollution on populations of marine organisms has so far not been demonst

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1985.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryDuring an eight years period the onset and development of piscivory of 0+ pikeperch was studied in the natural environment of a shallow, eutrophic Dutch lake.In some years the piscivory started as early as halfway June at a pikeperch size of circa 20 mm. The 0+ pikeperch predated mainly on the smaller 0+ smelt because these were the most slender preyfish available. The 0+ pikeperch is less and the 0+ perch is much less available because of their larger circumference. Small 0+ bream and roach became only available when their growth was retarded.The positively skewed size distribution of the 0+ pikeperch halfway June is precursory for the development of bimodality in the size distribution later in the season. A second modus of larger, piscivorous, 0+ pikeperch became relatively important in years when smelt was abundant. The survival rate of this category was appearantly higher than that of the smaller planktivorous individuals.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1985.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryIn laboratory research, the rainbow trout has become a counterpart to the white rat, because that fish is an adaptable species available in much of the developed world and stocks from egg through adult are available throughout the year. Moreover, many strains are recognized, and their propagation and laboratory maintenance are not particularly demanding. Also, knowledge of rainbow trout nutrition, husbandry, diseases, immune responses, toxicology, and carcinogenesis exceeds that of any other salmonid or coldwater teleost. The rainbow trout is the logical surrogate species in many studies of other salmonids.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1985.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryEnzym‐electrophoretic examination for species identification of wbitefish (Coregonus lavaretus wartmanni Bloch and C.l. macrophthalmus Nüsslin) of the upper pan of Lake Constance, Federal Republic of Germ

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1985.tb00423.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY