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.

Starker Nachwuchsjahrgang 2002 des Herings der westlichen Ostsee

Several fishery independent estimates of the year-class strength are necessary for the assessment and the management of the total fish stock. An index for the year-class strength of the spring spawning herring in the western Baltic Sea is estimated on the basis of larvae surveys in the most important spawning ground. The results indicate a strong year-class 2002.

Ist die Steigerung des dauerhaften Fischereiertrages durch Maschengrößenoptimierung möglich?

The management of a fish aimed at maximising the fishing yield of the managed fish stock. There are models for the yield optimisation since long time. They are used so far mainly to optimise the fishing mortality. Starting point of this paper is a number of fish of an age group of a fish stock. This age group is accompanied over its lifetime. A result of the investigations is that the term growth over-fishing is linked not as frequently assumed exclusive with a too large fishing mortality, but likewise with a mismatch of the mesh opening. The investigations show that the fishing yield increases with the fishing effort on condition that fishing is carried out with an optimised mesh opening. For the calculated example Baltic cod data are used. At present the cod is caught far before reaching the yield optimum. Now the fish is substantially too small when it is caught and did not reach its optimal mass at this time. Therefore the sustainable fishing yield could be increased considerably by the optimasation of the mesh opening. During the conversion from the state of the art to fishing with optimised mesh sizes, however, a loss of profit has to be expected. A further advantage of the mesh enlargement is an increase of the spawning stock size accompanying with it, since the fish is caught at a later age. By the use of substantially larger mesh openings the cod has the opportunity to spawn several times and generate descendants and this will also lead to an increased yield in future. In addition better prices could be obtained at the market by catching larger cod.

Entwicklung und Lage ausgewählter Fischbestände - Einschätzung des Internationalen Rates für Meeresforschung Ende 2000

During the autumn session of the ICES Advisory Committee for Fisheries Management (ACFM) the stock of the Arctic, Northern and Southern Shelf, North Sea and Skagerrak have been analysed and assessed, as well as the mackerel and horse mackerel, sardine, anchovy and Pandalus, eel and harp and hooded seals. For a number of stocks ICES recommends a reduction in fishing mortality. Moreover, ICES recommends for many stocks to establish recovery and management plans, to safe guarda continuous development of the stocks towards safe biological limits.

Die Lage der Fischbestände in Nordostatlantik, Nord- und Ostsee. Einschätzungen des Internationalen Rates für Meeresforschung im Frühjahr 2001

The spring session of ACFM gave advice for a number of stocks in the North Atlantic, North Sea and Baltic. The present assessment of the situation is given here for stocks of importance for the German fishery. These are: Blue Whiting: the stock size is rapidly decreasing due to high catches; ICES recommends a closure of the fishery. Herring (Atlanto-Scandian, Norwegian spring spawner): Stock is within save biological limits, weak recruitment of the recent years will lead to a further reduction of biomass. Herring (North Sea): revision of the assessment led to a different perception of the stock: SSB was in 2000 below Blim. Excellent recruitment will lead to an increase of SSB over Blim within this year, but ICES recommends to reduce fishing mortality on adults significantly. Herring (Baltic spring spawner in 22–24, IIIa): Still no increasing tendency is detectable. Herring (VIaNorth): stable. Redfish: generally further decreasing tendency observed, a reduction of the fishery is recommended. Signs of recovery visible only for two units. Greenland Halibut: State of the stock not quite clear, but slightly positive tendencies. The present fishing intensity should be reduced. Cod (Kattegat): Weak recruitment, outside safe biological limits. ICES recommends a closure of the fishery. Cod (22–24, Western Baltic): Stock situation unclear due to extensive migrations. F should be reduced by at least 10%.

Lage und Entwicklung ausgewählter Fischbestände. Einschätzung des ICES im Oktober 2001

During the autumn session of the ICES Advisory Committee for Fisheries Management (ACFM) the stock of the Northern and Southern Shelfs, North Sea and Skagerrak have been analysed and assessed, as well as the mackerel and horse mackerel, sardine, anchovy, Pandalus and Eel. 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.

Schwacher Nachwuchsjahrgang 2001 des Herings in der westlichen Ostsee

Several fishery independent estimates of the year-class strength are necessary for the assessment and the management of the total fish stock. An index for the year-class strength of the spring spawning herring in the western Baltic Sea is estimated on the basis of larvae surveys in the most important spawning ground. The results indicate a weak year-class 2001.

Die lage der Fischbestände in Nordostatlantik, Nord- und Ostsee. Einschätzungen des Internationalen Rates für Meeresforschung im Frühjahr 2000

The spring session of ACFM gave advice for a number of stocks in the North Atlantic, North Sea and Baltic. The present assessment of the situation is given here for stocks of higher importance for the German fishery. These are: Blue Whiting: the stock is still relatively high, this, however, will not last very long, due to too intense fishing. Cod in Kattegat: stock is outside safe biological limits. No immediate recovery in sight. Cod in 22–24 (Baltic): stock is inside save biological limits. F, however, is above the recommendation of the IBSFC. Greenland Halibut: state of the stock not quite clear. The present fishing intensity seems to be sustainable. Herring (Atlanto- scandian, Norwegian spring spawner): stock is within safe biological limits, weak recruitment of the recent years will lead to a reduction of biomass. Herring: for Baltic spring spawner in 22–24 and IIIa still no increasing tendency detectable. North Sea Herring: further increasing tendency, with 900 000 t over B lim, good recruitment. Herring in VIa: stable. Redfish: generally decreasing tendency observed, a reduction of the fishery is recommended. Signs of recovery, however, visible for some units

Einfluss des Tag-Nacht-Verhaltens von Fischen auf das Ergebnis hydroakustischer Messungen

Echo integration is an established method for stock estimation. However, this method is not free of errors like every other measuring method. Especially the variation between day and night behaviour of fish may lead to large measuring errors. A new method is represented detecting such systematic errors, exemplified by investigations during the international hydroacoustic survey on the spring spawning herring in the Norwegian Sea. For this method all measured sA-values are sorted by starting time of the measuring unit distance. In order to reduce random influences a moving average over five time intervals is computed. When displaying these values in a diagram makes it is very easy to detect systematic errors based on the differences in day-night behaviour. For both species, herring and blue whiting, stock estimations are calculated based on the measured sA-values and the results of the analysed trawl catches. The influence of the differnt day and night behaviour of herring on the results of its biomass estimation is rather low. For blue whiting the measured values were about three time higher during day time than during night time. The result of this investigation should initiate a change of the evaluation procedure for stock estimation based on hydroacoustic measurements.

24. Sitzung des FAO/WHO Codex Alimentarius Komitees für Fische und Fischerzeugnisse

Die 24. Sitzung des Komitees für Fische und Fischerzeugnisse wurde vom 5. bis 9. Juni 2000 erstmalig in Ålesund, Norwegen, durchgeführt. Die Tagung wurde von 140 Delegierten und Beobachtern aus 43 Mitgliedsstaaten und 3 internationalen Organisationen (EU, A.C.P. Generalsekretariat und Internationale Vereinigung der Fischinspektoren, IAFI) sowie FAO- und WHO-Personal (4) besucht. Die größten Delegationen stellten Frankreich (6), Kanada (6), Thailand (7), USA (10), Marokko (13) und Norwegen als Gastgeber (16). Die deutsche Delegation wurde von Dr. Achim Viereck (BML) geleitet. Weitere Mitglieder waren Dr. Jörg Oehlenschläger (BFAFi, Sprecher), Dr. Reinhard Schubring (BFAFi), Dr. Günter Klein (BgVV) und Dr. Matthias Keller (Bundesverband der deutschen Fischindustrie und des Fischgroßhandels). Die Sitzung, die von Peter Gullestad, dem norwegischen Generaldirektor für Fischerei, eröffnet wurde, leitete Dr. Bjorn Rothe Knudtsen, Regionaldirektor des norwegischen Direktorats für Fischerei und Aquakultur, Trondheim.

Der Krill im Südatlantik. Entwicklung der Bestände, der Fischerei und des Bestandsmanagements

Since 1976 the Institute of Sea Fisheries of the Federal Research Center for Fisheries, Hamburg, has been conducting long-term monitoring research on Antarctic krill in order to manage the stocks according to the precautionary approach. The krill stocks of the South Atlantic fluctuate seasonally as well as inter-annually in biomass and recruitment success. Following high densities in the late 1970s, the stocks are recently declining. Shortly after the onset of a commercial fishery the catches reached a maximum of around 500 000 t annually, but stabilized around 100 000 t during recent years. Actual survey results indicate mean krill densities in the South Atlantic of 21.4 g/m2, corresponding to 44 Mio. t. The potential yield and maximum catch rate was set at 4.0 Mio. t per year subdivided for the various CCAMLR Subareas. CCAMLR is expected to introduce further conservation measures to control the fishery in the convention area in the near future, however, there is still room for developing a krill fishery in the Antarctic.

Laichgebiete des Dorschs in der westlichen Ostsee

Analyses of the previous years showed that the reproduction of the Belt Sea cod stock (Gadus morhua morhua) is also very important for the cod stock of the central Baltic Sea (Gadus morhua calarias). Oeberst (1999, 2000) proved, that between 20 % and 50 % of the cods caught in the Bornholm Sea at the age of 2 or 3 years between 1994 and 1998, were spawned in the Belt Sea. On account of this large significance of the Belt Sea cod stock, information regarding the reproduction process are important. The goal of the article presented is the description of the actual spawning areas of the Belt Sea cod stock by means of the spatial distribution of the spawners based on characteristic parameters as the maturity stages and the proportion of the sexes. The basis for these analyses are data sampled between 1992 and 1999. The analyses showed that the actual main spawning areas in the western Baltic Sea were the deeper regions of the Kiel Bay, of the Fehmarn Bay and of the western Mecklenburg Bay. In these regions spawning cods were regularly observed with high intensity. Furthermore, the deeper basin of the Arkona Sea is an important spawning area.

Schwacher Nachwuchsjahrgang 2000 des Herings in der westlichen Ostsee

Several fishery independent estimates of the year-class strength are necessary for the assessment and the management of the total fish stock. An index for the year-class strength of the spring spawning herring in the western Baltic Sea is estimated on the basis of larvae surveys in the most important spawning ground. The results of this year’s herring larvae survey indicate a weak year-class 2000.

Zur Optimierung des Laboraufwandes bei Heringslarvensurveys im Greifswalder Bodden

Since 1977 larvae surveys have been carried out in the Greifswalder Bodden and the Strelasund every year to estimate an index of the year-class strength for the western Baltic herring stock. Different methods have been used to minimize the very extensive analytical work in the laboratory since 1993. As a further possibility the use of the mean dry weight of the larvae was investigated. This method was applied successfully to estimate the number of eggs in cod gonads. 88 samples of herring larvae were analysed. These experiments show that the use of the mean dry weight of herring larvae is not suited to reduce the work in the laboratory, because the accuracy of the estimates is unacceptable.

Das M74-Syndrom des Ostseelachses (Salmo salar): Symptome, Verbreitung und Ursachen

An overview is presented on the M74-Syndrome of Baltic salmon which is known since 1974 and which, since 1992, has caused considerable losses of artificially produced yolk-sac larvae in Swedish and Finnish hatcheries responsible for compensatory salmon stocking programmes. The syndrome only affects offspring of wild salmon ascending the rivers for spawning and not offspring derived from salmon broodstocks permanently kept in hatcheries. The syndrome seems to be restricted to the Baltic Sea where it has been recorded in all of the remaining Swedish (except the west coast) and Finnish salmon rivers as well as in populations of Estonian rivers and the Russian River Neva. In Sweden and in Finland, the syndrome has been recorded in recent years in offspring of up to 80 % of female salmon used for spawning and resulted in a larval mortality of up to 90 %. A nutrition-associated thiamine (vitamin B1) deficiency is considered as primary cause. However, other environmental factors seem to be involved in addition. There is concern that the syndrome constitutes a major threat with respect to the survival of the few still naturally reproducing populations of Baltic salmon.