Kabeljau-Discards in der Deutschen Bucht

The German trawlfishery on cod in the German Bight causes discards. Their amount since 1983 has been estimated. The losses of millions of fish finally is the reason for losses of thousands of tonnes of valuable landings. The fishermen therefore should improve the selection rate of their nets.

Die biologischen Voraussetzungen für einen guten Dorschnachwuchs verbesserten sich 1994 in der westlichen Ostsee

The investigations on the fecundity of cod from different areas of the Baltic Sea started in 1992. The samples were collected in ICES Sub-divisions 25 (Bornholm Sea). 24 (Arkona Sea) and 22 (Mecklenburg and Kiel Bay). This article surnmarizes the results of 435 analysed gonads from females of age groups 1 to 8 with total length of 24 - 116 cm of the years 1992 to 1995. The gonads were prepared and analysed according to the methods which were deseribed in Bleil and Oeberst (1993). The aim of the investigations is to estimate the reproduction potential of cod for different areas and years. For this reason the absolute and relative fecundity were analysed for estimating the dependence on the total length, for age groups and the weight of females. These data were estimated for the populations Gadus morhua morhua and Gadus morhua callarias. Preliminary results have shown that the absolute fecundity (fabs) is dependent on whole weight of the females. The influence of sub-divisions (SD) and years to the fecundity are very low. Additional to this data was calculated the population fecundity for the western Baltic Sea stock (SD 22 and 24). The numbers of produced ripe eggs within the western Baltic were estimated with 4055.59 x 10(9) for 1993 and 6949.85 x 10(9) for 1994.

Einfluß der Holtechnologie auf die Selektion von Grundschleppnetzen

A widespread belief among fishermen that sidetrawlers show a better selectivity than sterntrawlers was investigated in a comparative fishing exercise in the Baltic. In contrary to earlier observations during this experiment in May no essential differences with regard to the selectivity of the trawls used could be found for both types of fishing vessels. Possible explanations for the result are discussed.

Keine Erholung der westgrönländischen Grundfischbestände

Since 1991, the aggregate biomass of fish stocks inhabiting the West Greenland shelf stagnates at the lowest level. The latest survey results of cruise no. 152 conducted by FRV 'Walther Herwig III' do not indicate any improvements in state of the stocks, although no fishing effort was recently directed towards groundfish. The cod stock showed again a record low and is presently dominated by recruits of the year classes 1991 and 1993. Both year classes are considered to be weak and the cod stock is beyond the 'minimum biologically acceptable level'. Consequently, an increase in stock abundance is not expected either in short or long term. Other ecologically or economically important fish species, American plaice, redfish, wolffish and starry skate, were also found to have minimum stock abundances. By-catch estimates of juvenile groundfish taken by the shrimp fishery, operating at traditional grounds of cod and redfish fisheries, are indispensible. Analysis of climatological data from Nuuk/West Greenland indicates that climate during the past fourty years was characterized by two decades of anomalous warm conditions, and cooling which dominates the dimate since 1969. Anomalous cold events were encountered during 1983, 1984 and during 1992, 1993. Similar to the air temperature anomalies, autumn temperatures of the ocean surface layer indicate cold and warm periods during the past thirty years. In contrast to the colder than normal atmospheric conditions during the early nineties, however, the ocean conditions indicate intermediate warming.

Probennahme in der Barentssee zur Einschätzung der Schadstoffbelastung

Die Fischereibänke der nördlichen norwegischen Küste und der Barentssee einschließlich der Gewässer um spitzbergen und der Bäreninsel sind Fanggründe, aus denen beträchtliche Mengen an wertvollen Meeresfischen wie Kabeljau, Schellfisch, Seelachs, Rotbarsch und Schwarzer Heilbutt auf den deutschen Markt kommen. So wurden beispielsweise im Jahr 1993 allein von deutschen Fangschiffen aus diesen Gewässern angelandet: 2600 t Kabeljau, 430 t Schellfisch, 3700 t Seelachs, 500 t Rotbarsch und 13 t Schwarzer Heilbutt. Darüber hinaus gelangt noch eine beträchtliche Menge an Importen von anderen EU-Staaten und von Drittländern in die Bundesrepublik Deutschland, deren genaue Höhe schwierig quantifizierbar ist.

Trenngitter - eine Alternative zu den Trichternetzen in der Garnelenfischerei

Experimental fishing trials were conducted in the Elbe Estuary using an experimental 3 m-standard beamtrawl. To avoid the by-catch of fish, a sorting grid was used. The elliptical grid was constructed of 6 mm diameter stainless steel bars with a spacing of 13 mm between the bars and housed in a cylindrical frame of 400 mm diameter. It was installed in the extension piece just in front of the codend angled at 45°, with a fish outlet at the top. A series of 10 tows of 15 minutes duration at a towing speed of 3 kn was done. The catch of the main codend was compared with the catch separated by the sorting grid. This achieved a reduction of 56 % of plaice (Pleuronectes platessa), 75 % of flounder (Platichthys flesus), 99 % of whiting (Merlangius merlangus), 94 % of cod (Gadus morhua) and 49 % of smelt (Osmerus eperlanus) with a mean loss of 43 % of shrimps (Crangon crangon). English grid trials in the Humber estuary using a flapper set or guiding funnel in front of the sorting grid device demonstrated reasonable lower escapement rates for fish and shrimps.

Internationaler BMB/ICES-Workshop "Fischkankheiten und Parasiten in der Ostsee"

From 25 November until 8 Deeember 1994, a sea-going workshop with the above title was carried out on board RV "Walther Herwig IlI" under the umbrella of the Baltie Marine Biologists (BMlJ) and the International Council for the Exploration of the Sea (ICES). Under the co-convenorship of the first two authors of this paper, 11 seientists from 8 of the 9 countries bordering the Baltic Sea (except Sweden) actively involved in research monitoring into fish diseases/parasites participated. The main reason for holding the workshop was that, although fish disease monitoring programmes on the abundance and spatial distribution of fish diseases/parasites are being carried out by some of the countries bordering the Baltic Sea, there is still a striking lack of seientific information as compared to other seas, such as the North Sea. Moreover, since new fish disease monitoring programmes have recently been started (mainly by the new Baltic republics Latvia and Estonia, which recently became ICES-member countries) or are planned for the near future (Lithuania), BMB as weil as ICES felt the need for a interealibration and standardization of methodologies applied during fish disease/parasite surveys for the specific conditions in the Baltic Sea. Therefore, the major objectives of the workshop were -to obtain information about the disease/parasite prevalence in Baltic (Platichthys flesus) and other abundant fish species along a transect from the western (Mecklenhurg Bight) to the eastern (Gulf of Finland) Baltic Sea to be used as a baseline for future studies, -to intercalibrate methodologies applied for sampling, diagnosis of diseases/parasites, reporting and analyses of disease data, -if necessary, to recommend standard methodologies to be used for fish disease/parasite monitoring programmes under the specific conditions in the Baltic Sea. Although the data have yet not been completely analyzed, there is indication for some pronounced spatial trends regarding the prevalence of certain diseases/parasites, mainly for Iymphocystis and skin ulcerations in flounder but also for diseases and parasites of cod (Gadus morhua) which can be seen in figures 2 and 4. Recommendations for standard methodologies will later be published elsewhere.

Bewertung von Frische- und Verderbsindikatoren bei der Eislagerung von Schollen (Pleuronectes platessa)

An iced storage experiment with plaice was conducted during the 1l5th cruise of FRV "Walther Herwig II" in the North Sea. Iced stored plaice were rated by sensory methods as saleable until day 18 of iced storage and as edible until day 20. In addition to the sensory tests the Fischtester VI readings and the pH-value measured in muscle homogenate proved to be useful freshness indicators, while TVB-N is a typical spoilage indicator.

Neue Chance für Scholle und Kabeljau in der Nordsee

Two surveys in the German Bight revealed a relatively good recruitment for plaice and cod. However, with the current high effort and uneconomic way of fishing, most of these fish will end as discards. To protect young plaice during the winter months an increase of the mesh opening in beam trawls within the plaice box is suggested. Therefore, the fishermen are called upon to make a more considerated selection of their nets.

Gute Kabeljau- und Schellfischvorkommen bei der Bären Insel

Biological investigations were carried out onboard the commercial freezing trawler "Kiel" in the Bear Island area in May/June 1995. Data will be used as German contribution to the assessments of the ICES "Artic Fisheries Working Group". Concentrations of cod were found southwest of Bear Island. Catches ammounted to 5-60 t/haul. Relatively good catches (5-25 t) with high proportions of haddock (40-80 %) were observed to the northwest of the island. Length- and age distributions as well as preliminary results of stomach- and gonad- investigations are presented.

Untersuchungen zur Aufzucht von Dorschen (Gadus morhua morhua) der Westlichen Ostsee. Teil II: Aufbau und Hälterung eines Laichfischbestandes sowie Erbrütung der gewonnenen Eier

In 1993 and 1994 hatching and rearing of cod eggs and larvae from the western stock was carried out aiming at data about the reproduction biology of this species. This paper describes the hatching methods and first results of the correlation between various biotic and abiotic factors, naturally fertilized eggs from a broodstock, and the amount of viable larvae.

Einfluß von Anlagen der Offshore-Industrie auf die Fischerei in der Nordsee

From the beginning of the oil and gas exploration in the North Sea the impact of offshore installations, especially pipelines, on the fishery has been thoroughly discussed and investigated. Since fishing activities in the vicinity of pipelines are not prohibited, special precautions have to be taken to prevent towed fishing gear from being fouled by a pipeline. Until now all recommendations for the installation of pipelines are based on the results of tests with trawls crossing one pipeline. New problems will arise if parallel pipelines are installed as planned in the near future.