If you are interested in comprehensive and up-to-date information on the state of fish stocks that are important for the German market, then you should visit the "Fish stocks online (Fischbestände online)" webpage.
There you will find short descriptions of the fish species, structured according to specific fish stocks. This structure is necessary since these reproduction units may develop differently over time. It also describes all other aspects that may be relevant to the assessment of sustainable fisheries. All information is based on scientific publications and advice.
The information is compiled by the Thünen Institute of Baltic Sea Fisheries and is for the most part updated annually, mainly on the basis of published reports from intergovernmental scientific organizations. The facts are explicitly presented without any assessment or evalution. Also it should be mentioned that the classification of the state of the stocks or species according to various criteria is not a rating, but rather an allocation into a scientifically specified grid. You will not find general reviews or group valuations of fish species or fishing methods here.
Unfortunately, this service is only available in German. Follow this link to Fish stocks online (Fischbestände online).