Zweikampf im Wattenmeer : Wird die heimische Miesmuschel verdrängt?

Since a couple of years, the introduced Pacific oyster (Crassostrea gigas) is spreading out in the Wadden Sea off the German North Sea coast where it competes with the native blue mussel (Mytilus edulis). First catches of the new species have now been observed in fishing surveys.

Die EU-Förderung der Fisch verarbeitenden Industrie und das EU-Datenerhebungsprogramm

A considerable amount of national EU funds for supporting fisheries has been transferred to the German fish processing in-dustry. The recently ratified European Fisheries Fund (EFF) again provides a significant sum. Yet the EU is lacking a data pool of sufficient precision, which is required as a basis to develop apt EU regulations in the future. Regulation No. 1639/2001 of the EU Commission commits the member states to collect these data. In this paper specifics of the data to be collected and the collection procedure are presented and linked to the CFP and to characteristics of the German fish processing industry.

Eine zusätzliche Möglichkeit für die Ostseedorsch-Fischerei: Steerte aus 90° gedrehtem Netztuch

In 2004, comparative selectivity investigations were made with the now legal BACOMA codend of 110 mm mesh opening and alternative codends made of netting turned 90° of similar mesh openings on both commercial boats and on research vessels. The results show a certain variability of the BACOMA results – depending on ship type and season (L50 varying between 36,8 and 40,6) – and a general equal efficiency of codends made of netting turned 90° of the same mesh opening. Underwater observations and reduced performance of codends of equal circumference in meshes as the joining round at the end of the tapered part of the trawl indicate the need to reduce the relation of the cir-cumferences of codend and extension to 1 to 0.7 to achieve optimum fit and selectivity.

Sind die bestehenden Regulierungsmaßnahmen für die Flunderfischerei in der südwestlichen Ostsee sinnvoll?

The reliability of the international minimum landing size of 25 cm for the flounder stock of ICES Sub-divisions 24 and 25 as well as national bans on landing female flounder during the spawning time is investigated on German samples taken in Sub-division 24. The results of the analyses of growth, sex ratio, the proportion of mature flounder, and yield curves show that 25 cm is a convenient regulation measure but it would be reliable to have an international ban on landing female as well as male flounder during spawning time.

Die Überwachungsprogramme der internationalen Meeresschutzkonventionen für Nord- und Ostsee

The international conventions for the protection of the marine environment of the North-east Atlantic Ocean including the North Sea (OSPAR) and the Baltic Sea (HELCOM) as well as the International Council for the Exploration of the Sea (ICES) have modified their structures in the recent years towards a strategy directed approach. Committees and working groups have partly changed only their names but in many cases also the scope of their subjects. In the last two years activities have been initiated to coordinate the tasks of the marine conventions and the European Union and to merge them as much as meaningful and practicable, under a common EU Marine Strategy. This article will reflect how the organisational structures have changed since the last restructuring in the first half of the nineties, and how the contaminant and bioeffect monitoring activities of the Federal Research Centre for Fisheries are implemented in these international conventions.

Die Fischerei im Nordostatlantik im Jahre 2004

Since 1990 North-east Atlantic fish species – arctic cod, saithe, haddock, redfish and Greenland halibut – have been investigated by on-board observers on the German commercial trawler FMS Kiel. These investigations are part of the national data collection regulation established by the European Union in recent years. Collected data are basic data for the scientific assessment of these important fish stocks of the European fisheries. The results of the observed cruises are used by the Arctic Fisheries Working Group of the International Council for the Exploration of the Seas (ICES). Biological investigations were carried out in Norwegian waters and the Barents Sea (ICES Divisions IIa and IIb) on board FMS Kiel in January to March and in August/September 2004. This report presents results of these cruises and an overview about the general fishery situation in 2004.

Die Reproduktion von Dorschen (Gadus morhua L. und Gadus morhua callarias L. ) in der Ostsee unter besonderer Berücksichtigung der Arkonasee. Teil I: Allgemeiner Verlauf des jährlichen Reifeprozesses und der Laichaktivitäten in den verschiedenen Gebieten

From 1993 to 2003 special surveys were conducted to analyse temporal and spatial aspects of the spawning activities of cod in the Baltic Sea. The ICES advice for cod in the Baltic Sea is based on yearly stock assessments of two separate stocks the western (SD 22 – 24) and the eastern stock (SD 25 – 32). Both stocks are characterized by different spawning seasons. The general progression of the maturity suggests that two types of development can be distinguished. In the western Baltic Sea (SD 22) the maturity development is temporal stable, with a relative short, main spawning period from March to April - spring spawner. In the Arkona Sea and Bornholm Basin the main spawning season starts in June and probably finishes in September - summer spawner. The proportion of spawners in summer is significantly higher than in spring in the Arkona Sea and Bornholm Basin. This again underlines the importance of the Arkona Sea for the reproduction success of the eastern Baltic cod stock. The analysis furthermore show, that the proportion of male spawners was significantly higher than the proportion of female spawners in all areas and the investigated months. This observation suggests that the reproductive success is only limited by the number of female cod which participates in the spawning process.

Die Reproduktion von Dorschen (Gadus morhua L. und Gadus morhua callarias L.) in der Ostsee unter besonderer Berücksichtigung der Arkonasee. Teil II: Statistische Analysen zum Anteil reproduktiv aktiver Dorsche in Bezug auf gebietsspezifische Unterschiede und Gemeinsamkeiten, sowie deren mögliche Ursachen.

Surveys were conducted to analyse temporal and spatial aspects of the spawning activities of cod in the Baltic Sea from 1993 to 2003. Part I of the article describes the general maturity development and the spawning activities in the western Baltic Sea, the Arkona Sea and the Bornholm Sea. The studies suggest that two types of spawner can be distinguished, the spring spawner in the western Baltic Sea and the summer spawner in the Arkona Sea and the Bornholm Basin. The descriptive analysis is supported by statistical studies presented in this article. It is shown, that the proportion of spawning individuals is significantly higher in summer than in spring in the ArkonaSea and the Bornholm Sea. Furthermore, it is shown that reproductive mixing of both types of spawner is possible in the Arkona Sea in May/June due to the hydrographical conditions in the Arkona Sea which were suitable in 8 of 10 years for successful reproduction of both Baltic cod stocks, and that spatial expansion of spawning activities of the eastern Baltic cod stock into the Arkona Sea is positive correlated with the size of spawning stock in the Bornholm Sea.

Wer fischt was? – Gemischte Bodenfischereien und ihre Auswirkungen auf die wichtigsten Nutzfischbestände in der Nordsee

Cod, haddock, whiting, saithe, plaice, sole and Norway lobster are 7 main target species of the demersal mixed fisheries in the North Sea, Skagerrak and Eastern Channel. Gadoids and Norway lobsters are mainly taken in the nor-thern North Sea by towed gears except beam trawls while the flatfish fisheries are conducted in the southern North Sea mainly using beam trawls. Recently, the central North Sea appears less fished by demersal gears. Towed nets including seines and beam trawls equipped with meshes of more than 100 mm resp. more than 80 mm were identified as the main gears effecting the depleted cod and reduced plaice stocks. The saithe sector, using towed nets with meshes of more than110 mm, longlines, gill nets and others, appears to affect the 7 species to a lesser extend. These results support the interim effort limitations by gear types, vessel and month as enforced by the European Commission since 2003. TAC regulations alone are considered inefficient to sustainably harvest stocks by mixed fisheries. A fleet-effort management method is developed estimating the fleets’ effects based on the sum of partial exploitation rates of the species in mixed fisheries weighted by the ratio of the precautionary reference Bpa and the actual SSB size as ecological quality objective. Applying such fleet effort management could result in increased catch possibilities of some stocks by fleets selecting mainly few and non-overexploited stocks while respecting precautionary management constraints in minimum SSB or maximum exploitation rates at the same time.

Die Anwendung molekulargenetischer Verfahren in der fischereiwissenschaftlichen Forschung - Trennung von Fischpopulationen

The discrimination of stocks and separate reproductive units within fish species to facilitate fisheries management based on biological data has always been a challenge to fisheries biologists. We describe the use of three different molecular genetic techniques to detect genetic differences between stocks and closely related species. Direct sequencing of the mitochondrial ND3 gene describes the relationship between different aquaculture strains and natural populations of rainbow trout and revealed genetic homogeneity within the hatchery strains. Microsatellite analyses were used to explore the differences between redfish species from the genus Sebastes and to verify populations structure within S. mentella and S. marinus. This lead to an un equivocal discrimination of the species and an indication of populations structure within those species in the North Atlantic. The Amplified Fragment Length Polymorphisum (AFLP) methodology revealed genetic differences between Baltic and North Sea dap (Limanda limanda)and a possible population structure within the North Sea.

Die Qualitäts-Index-Methode (QIM), ein verlässliches Instrument zur sensorischen Bewertung der Frische von Fisch

Fish research institutes in Europe have made considerable effort in developing rapid, objective sensory methods for evaluation of fish freshness. The Quality Index Method(QIM) has been recommended for a European initiative regarding standardisation and harmonisation of sensory evaluation of fish. QIM-schemes have been developed for various common European fish species. Research has now provided the industry with a convenient, objective and powerful tool for measuring freshness of fish kept in ice Further research is needed to evaluate the applicability of QIM for fish handled, stored and processed under different conditions. However, for progress and development of QIM it is now very important that the fish sector implements QIM in fish auctions and the quality management system of the fish processing plants.

Einfluss von Reifung und technologischen Behandlungen auf die Proteine des Rogens von Regenbogenforellen (Oncorhynchus mykiss)

The use of differential scanning calorimetry for investigating the yolk proteins of the roe of rainbow trout allows to monitor the influence of maturation and vitellogenesis which modifies the DSC curves with regard to transition temperature and enthalpy. Two endothermic peaks become more and more pronounced with increasing maturation of the roe. However, it is still not known which protein fraction is represented by each of the peaks. DSC curves of yolk protein depend on fish species. They are also influenced by technological treatments. Further investigation is necessary to discover whether or not yolk proteins of other fish species are influenced in the same manner by maturation and vitellogenesis and which protein fraction represent the individual peaks.

Die Fangmengen an Nordseegarnelen und fischereilicher Aufwand im europäischen Vergleich - Langzeitserien und saisonale Übersicht

Among other tasks the “Working Group on Crangon Fisheries and Life Cycle” of the “International Council for the Exploration of the Sea” collects data on landings and effort in the North Sea brown shrimp fisheries by country. Landings per unit effort data are calculated and all are compared on basis of long-term series as well as on seasonal basis. The development for each country is described and compared for the year 2001 to the ten-year average from 1992 to 2001 were possible, as some data are missing especially for the Netherlands. While the Dutch and British fleets increased their landings substantially in 2001 compared to the previous years, Danish,German and Belgian fishermen had reduced landings. There are regional differences in fishing pattern between the countries, especially Denmark versus the rest of Europe. Effort measures remain incomparable between the countries, and fluctuations in landings per unit effort data seem to be in a normal biological range, giving no reason for concern at present for the situation of brown shrimp stocks in the North Sea. An improvement of the data basis is required and possibly achievable by the EU logbook system being in force for brown shrimp fisheries as well.

Die nordostarktische Fischerei im Jahre 2003

Seasampling of the important northeast Arctic fish stocks cod, saithe, haddock, redfish and Greenland halibut was continued in 2003. The sampling is part of the European data sampling directive on commercial fisheries established in recent years. This directive is relevant for European waters as well as for other areas where quotas have been assigned for European community member states. Furthermore, the results of these samplings are used as German basic data for stock assessments of the “Arctic Fisheries Working Group” of the International Council for the Exploration of the Seas (ICES). This report presents results of biological investigations which were carried out in ICES divisions IIa and IIb on board FMS “KIEL” in January/February and July/August 2003. The last section summarizes results and recommendations on the scientific assessment of the northeast Arctic fish stocks.