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Since 1928 and over the history of German fishing for brown shrimp ( Crangon crangon L.), several investigations have been made examining the by-catch of this small-meshed fishery. By-catch of commercially valuable fish, particularly flatfish species, has always been a matter of concern. The amount of by-catch comprising fish and invertebrates may actually be high, but figures discussed in public are biased by including discarded undersized shrimp, the target species, and dead material. Many changes in the equipment and practices of the fishery have occurred through the decades. As a result, the overall balance between consumption shrimp, by-catch and undersized shrimp has changed in a positive sense. Those fish still taken as by-catch despite the use of more selective trawls are often discarded and no longer landed for reduction purposes, leaving a chance to survive. Their species spectrum is largely stable over time. In this paper, detailed considerations are made in the particular case of North Sea plaice ( Pleuronectes platessa L.), which are abundant in the by-catch and is a commercially important species. Any large numbers discarded must be regarded in the light of high numbers of offspring, the large discards of the flatfish fishery and the high natural mortality of juvenile plaice. From that the conclusion is drawn, that the German shrimp fishery meets criteria of sustainability in respect to the target species and by-catch situation. [ABSTRACT FROM AUTHOR]

Time series on Crangon crangondensities in the German Wadden Sea show a considerable degree of interannual variability, for the entire region in spring and in autumn as well as for three subareas, North Frisia, East Frisia and Elbe estuary. Across the entire survey area C. crangondensity was inversely related to water depth. In autumn after the recruitment, settlement shrimp densities are correlated across a larger spatial scale (>100 km longshore), whereas in spring the overwintering adult spawning stock is uncorrelated across subareas. Interannually, extreme density variations can develop even over a short time span of 1 yr. On a large spatial scale shrimp abundance in autumn was correlated with year-to-year changes in physical environmental and biological parameters, winter water temperature, autumn river runoff and the winter NAO index. On a regional scale (North Frisia), density of gadoid predators was an additional component affecting shrimp stock abundance. No correlations to such parameters could be detected for the C. crangonstock in spring. Possible causes for the spring situation and additional sources for variability are discussed. [ABSTRACT FROM AUTHOR]

The mutagenicity of hexachloro-1,3-butadiene and its S-conjugates 1-(glutathion-S-yl)-1 ,2,3,4,4-pentachloro-1,3-butadiene (GTB), 1,4-(bis-glutathion-S-yl-1,2,3,4-tetrachloro-1,3-buta-diene (BGTB) and 1,4-(bis-cystein-S-yl)-1,3-but adiene (BGTB) was investigated in Salnwnella typhimurium TA100 using a modified preincubation assay. GTB was a direct-acting mutagen; the mutagenic potency of GTB was markedly enhanced by rat kidney nucrosomes or mitochondria and less so by cytosol. The ba-conjugates BGTB and ECFB were not mutagenic in the strains TA100, TA2638 and TA98. Purified HCBD was not mutagenic either without exogenous metabolic activation or with rat liver microsomes fortified with NADPH. Preincubation with rat liver micro somes and glutathione resulted in an unequivocal mutagenic activity of HCBD which was increased by additional inclu sion of rat kidney microsomes. The cysteine conjugate β-lyase inhibitor aminooxyacetic acid decreased the mutagenicity of HCBD and its S-conjugates. These results provide strong evidence that formation of the conesponding monoglutathione S-conjugate from HCBD and subsequent cleavage of this conjugate by γ-glutamyltranspeptidase and β-lyase may be responsible for the nephrocarcinogenicity of the parent compound in vivo, whereas formation of the bis-glutathione S-conjugate probably plays no role in the organ specific effects of HCBD. [ABSTRACT FROM PUBLISHER]