Horizontale Trennblätter in Trawls zur Verringerung von Discards in der Ostsee

A primary objective of the Common Fishery Policy of the European Union is the reduction of discards and unwanted by-catches in the fishery. In principle this could be achieved if the catching methods were optimised for this. Still high numbers of undersized flatfish are caught in the bottom trawls. Although EU regulations make the use of the BACOMA codend mandatory in the Baltic Sea cod areable to escape through square mesh escape window of the BACOMA net the whereas flatfish still remain in the cod-end. Gear experiments have been carried out with the aim to better separate cod from the flatfish fraction already when entering the rear belly, making use of the natural behaviour of the fish, i. e. the preferred swimming distance from the bottom of the net in the funnel. As cod have a natural tendency to keep a relativly great distance from the bottom, flatfish tend to stay close to it. It was attempted to separate both fractions by splitting the funnel into an upper and lower part with a horizontal panel. This wastested for two different nets, a cod trawl to separate cod from flatfish, and an eel-trawl to separate cod and flatfish from eel. Cod and flatfish separation is best at a panel distance of 50 cm from the bottom. Thus, 74 % of the cod were found in the upper panel, whereas 75 % of the flounder were in the lower section. A separation of eel from cod was however not possible, since eel tend to rise to the upper part of the net, together with cod.

Der PAH-Metabolit 1-Hydroxypyren in der Galle von Klieschen (Limanda limanda) aus Nord- und Ostsee

Due to their carcinogenic properties, polycyclic aromatic hydrocarbons (PAH) are important environmental contaminants which may lead to increased levels of neoplastic aberrations in fish liver. To measure the PAH contamination of fish, concentrations of PAH metabolites were determined in the bile. The main metabolite 1-hydroxypyrene was determined in concentrations from < 0.8 to 189 ng/ml in bile of dab caught in the North Sea and the Baltic Sea re-spectively. The concentrations are comparable to levels of 1-hydroxypyrene measured in cod and herring from the Baltic Sea. The highest concentrations in dab bile were measured in fish from the inner German Bight and the Kiel Bight.

Zustand und Entwicklung ausgewählter Fischbestände Einschätzung und Empfehlungen des ICES im Jahr 2004

The state of North Atlantic, Baltic Sea and North Sea commercially exploited fish stocks are assessed annually by the International Council for the Exploration of the Sea (ICES). Estimates of the stock size (biomass), recruitment, landings, current exploitation rates and of future harvesting possibilities are provided for those stocks where sufficient information is available to conduct a full analytical assessment. For all other stocks, only landings and stock trends can be given. This paper presents the development of north-east Atlantic fish stocks which are of general or specific interest for the German fishery and fish industry. Generally, it may be concluded that most pelagic fish stocks, such as herring, sprat, mackerel, and blue whiting, are in good condition, while the majority of the demersal stocks, like cod, plaice or whiting are in critical state. There are, however, a number of remarkable exceptions to this pattern.

Fischereisituation, Probennahme und Zustand der Nutzfischbestände im Nordostatlantik im Jahre 2002

NE-arctic cod, saithe, haddock, redfish and Greenland halibut are important fish stocks of the European fisheries. In many European countries national data sampling projects on commercial fisheries have been established in recent years. Since 1990 German investigations in the NE-Atlantic have been mainly carried out on the commercial trawler FMS KIEL. The results of these sea 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). Biological investigations were carried out in Norwegian waters, the Svalbard area and the Barents Sea (ICES Divisions I, IIa and IIb) on board FMS KIEL in March and October/November 2002. This report presents results of these cruises and an overview over the general fishery situation in 2002. Finally, results and recommendations on the scientific stock assessments of cod, saithe, haddock, redfishand Greenland halibut are reported.

Netzmaterial und Selektivität in der Ostseedorschfischerei

Since some time fishing gear scientists express their concern over an observed tendency of the commercial fishery to proceed from codend netting yarns of 3 to 4 mm to higher values or to switch to the use of double instead of single yarn. A recent large EU-financed project collected statistical evidence on the detrimental effect of such behaviour on the selectivity of the codends. In this context data on cod are very scarce. German-Polish experiments in the Baltic from 1999 to 2001 aimed at filling this gap. The investigations prove a clear evidence of a negativ ecorrelation between netting yarn diameter and selectivity factor and/or L50. In addition they demonstrate a clear negative effect on selectivity when switching from single to double yarn The effects are of an order of magnitude that counteracting effects as catch size are masked and support the decision of the IBSFC to define maximum yarn diameters both for single and double yarn netting. A measuring instrument for the enforcement of these new regulations was introduced right in time.

Kabeljaukrise in der Nordsee erfordert neue bestandserhaltende Maßnahmen

The European Commission has claimed a fundamental revision of the European Common Fisheries Policy in its Green Paper (EC 2001) by highlighting the reasons of continued overfishing of a number of valuable demersal fish stocks. Quotas in excess of scientific recommendations, fleet over capacities and poor enforcement of management decisions were identified causal for major stock and yield reductions while gaps in scientific advices were also criticized. The depleted cod stock in the North Sea, Skagerrak and Eastern Channel is the most prominent example. Existing and proposed management regulations were analysed by an expert group which met with fishing industry consultations in Brussels during 28 April – 7 May 2003. Depending on compliance with new technical regulations since 2000, the cod stock and its exploitation was found only marginally effected, while whiting displayed immediately significant losses in yield over long term and short term losses in haddock yields were reversed in substantial gains, also in SSB. However, reduction in fishing effort was found more effective in recovery potential than technical changes including closed areas, for which detailed information about variation in distribution of the stocks and the fisheries are required. Such effort reductions would reduce not only landings but also unregulated discarding, which is believed to be a major reason of the failure of the management measures in mixed fisheries. Recent trends in fishing effort of European fleets could not be quantified due to persistent data deficiencies.

Ein neues Messgerät zur Kontrolle der Maschenöffnung in der Fischerei

At present both the wedge gauge and the ICES mesh gauge are used to examine the mesh opening of trawl cod-ends. A thorough investigation of both instruments by an EU project (MESH) has revealed a number of deficiencies. This has lead to the conclusions to not further recommend the use of both devices but to go for the development of a complete new measurement tool. This is presently progressing in a further EU project named OMEGA. Prototypes of the new device have been produced and a number of introductory tests have already been made. This contribution reports on further laboratory tests carried out at the Institute for Fishing technology and Fish Quality with special emphasis on netting yarn diameters below 4 mm. The results demonstrate further yarn size depending inaccuracies of the wedge gauge and support the rapid introduction of the newly developed measurement instrument.

Zustand und Entwicklung ausgewählter Fischbestände: Einschätzung des ICES im Frühjahr 2003

During the spring session of the ICES Advisory Committee for Fisheries Management (ACFM) 48 stocks assessed by 7 Working Groups have been analyzed and reviewed, among these all herring stocks in the ICES area, blue whiting and most demersal stocks in the Baltic, Arctic and North-Western area. As in previous years, ICES recommends a reduction in fishing mortality for a number of stocks or even the establishment of recovery and management plans, to safeguard a continuous development of the stocks towards safe biological limits. ICES recommended a 90% reduction of the cod fishery in the Baltic Sea, while most of the herring stocks are in good condition.

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.

Zustand und Entwicklung ausgewählter Fischbestände: Einschätzung des ICES im Herbst 2003

During the autumn session of the ICES Advisory Committee for Fisheries Management (ACFM) 58 stocks assessed in 7 Working Groups have been analyzed and reviewed, among these the demersal stocks in the North Sea and the Mackerel stock. As in previous years, ICES recommends a reduction in fishing mortality for a number of stocks or even the establishment of recovery and management plans, to safeguard a continuous development of the stocks towards safe biological limits. ICES reiterated last year’s recommendation to close the directed cod fishery and any fishery taking cod as by-catch in the North Sea, west of Scotland and in the Irish Sea. This year, the stocks of plaice in the North Sea, southern hake and southern anglers are (among others) in a critical state and in urgent need of protecting or rebuilding measures. This will again have an enormous impact on almost all mixed fisheries in the European Union.

Sind südliche Arten in Nord- und Ostsee auf dem Vormarsch?

The long and warm summer 2003 resulted in water temperatures of about 2°C above the average. This promoted the immigration of southern species like the Anchovy, the Sardine, the Red Mullet and different Squid species. The possible conclusions of such invasions concerning the ordinary species of the area are rather contradictory: For the Western Baltic a positive correlation between the occurrence of Anchovy and a good Cod year-class is shown. For the southern North Sea, stomach investigations of Squid make a negative effect on fish eggs and larvae more likely.

Veränderungen sensorischer und instrumenteller Parameter während der Gefrierlagerung von Ostseedorsch (Gadus morhua) bei unterschiedlichen Temperaturen

Changes in sensory and instrumental quality parameter sand in thawing drip, cooking drip and total drip loss of frozen stored Baltic cod fillets (Gadus morhua) at different storage temperatures were investigated. Cod fillets stored at –20 °C and –30 °C exhibited the lowest drip losses and obtained the highest sensory scores. Drip losses were found to be highest in cod fillets stored at –10°C and in double frozen fillets stored at –20 °C. These two experiments also gave the lowest sensory scores. The texture parameters increased during storage parallel with storage time. The waterbinding capacity was lowest at –10 °C and almost constant at –30 °C. There is a good correlation between the sensory scores for “tough” and the instrumental texture measurement for hardness and chewiness.

Lage und Entwicklung ausgewählter Fischbestände: Einschätzung des ICES im Juni 2002

During the spring session of the ICES Advisory Committee for Fisheries Management (ACFM) the stocks of the Northern Pelagic and Blue Whiting, North Western, Baltic, Arctic and Deep Sea Working Groups have been analysed and assessed, as well as the Nephrops stocks. As in previous years ICES recommends a reduction in fishing mortality for a number of stocks. Moreover, ICES recommends for many stocks to establish recovery and management plans, to safeguard a continuous development of the stocks towards safe biological limits. Detailed recovery plans were proposed for cod and hake in the North Sea.

10 Jahre Untersuchungen zur Reproduktionsbiologie des Dorsches im Institut für Ostseefischerei

The reproduction biology of cod is one of the main re-search topics of the Institute of Baltic Sea Fisheries at Rostock. It was defined 10 years ago when the Institute was formed. Since then results have been published in a number of publications. This paper summarizes the main results of the past decade ant outlines necessities for future research in cod reproduction biology in the Baltic Sea.

Zustand und Entwicklung ausgewählter Fischbestände - Einschätzung des ICES im Herbst 2002

During the autumn session of the ICES Advisory Committee for Fisheries Management (ACFM) 58 stocks assessed in six Working Groups have been analysed and reviewed, among these the demersal stocks in the North Sea and the Mackerel stock in the North East Atlantic. As in previous years, ICES recommends a reduction in fishing mortality for a number of stocks or even the establishment of recovery and management plans, to safeguard a continuous development of the stocks towards safe biological limits. ICES recommended the closure of the directed cod fishery and any fishery taking cod as by-catch in the North Sea, west of Scotland and in the Irish Sea. This will have a significant impact on the mixed round fish fisheries targeting haddock and whiting.