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.

Fangtechnische Möglichkeiten zur Reduzierung des Beifangs von Meeresenten in der Dorschfischerei mit stationären Fanggeräten

The present contribution summarizes results of fishery investigations with gillnets and longlines in the winter cod fishery which had been carried out in the western Baltic region from 1996 to 1999 by the Bundesforschungsanstalt für Fischerei with financial aid of the country Schleswig-Holstein. The main goal of these investigations was to point out technological possibilities for a reduction of unwanted bycatches of sea ducks in gillnetting. As it is obviously impossible to reduce the local and temporal bycatch problem by means of different gillnet constructions or tactical measurements, only the temporary avoidance of fishing grounds with high abundance of ducks or the change to longlining as catch method with reduced duck bycatches may be an effective solution.

Die Situation der Makrelen- und Stöckerbestände. Der deutsche Beitrag zur internationalen Bestandsabschätzung

The question has not yet been completely solved whether or not the mackerel and horse mackerel stocks in the waters from the Bay of Biscay to the Atlantic off the Norwegian coast are independent unit stocks or must be regarded rather as one stock with distinct stock components. The stock definition, however, is the basis for fishery management and is fundamental for the exploitation of the stocks. For this reason the extensive mackerel and horse mackerel egg survey carried out in 1998, is of high importance and significance for the fishery management of the two species. The survey has begun in January in Iberian waters and will eventually end in the autumn north of Scotland. To cope with this task research vessels of eight European nations are participating.

Leistungsmessung an Bord von Fischereifahrzeugen zur Kontrolle der 300-PS-Begrenzung in der Schollenbox

For monitoring of the engine power of fishing vessels permitted for fishery in the plaice box with engine power of 300 HP or less at sea three different portable power measurement systems are developed and tested. A system measuring the twist of the propeller shaft by two divisible gearwheels mounted on the shaft worked well at shafts with roller bearing at both sides of the measured interval of 100–300 mm length. Only at a very few fishing vessels this system is applicable and therefore for monitoring purposes not suitable. The application of a commercial available system measuring the stress at the surface of the shaft was simplified for application by non experts. The torque is measured by strain gauges. The calibration of the system, measuring and recording of the power is done by a PC automatically. A small polished facet on the shaft protected against oxidation is needed for easy and quick application. In this case the system can be used by technical personnel of supervision boats for monitoring of the engine power at sea in a short time. A third power measurement system determinates the torque by measuring the displacement of two supports clamped on the shaft at a distance of 100 mm. The displacement is measured by a micrometer gauge mounted on one of the supports. Readout of the rotating gauge display is possible taking advantage of stroboscopic effect. The system needs no conditioning of the shaft and can be used by non technicians. The development is not finished until now and some additional investigations and tests are required. Additional measures for monitoring of the power on fishing vessels by self recording power measurement systems and sealed fuel racks with limited injection are reported and discussed.

Untersuchungen zur Sensibilität von Seefischen an Bord

First orientating investigations of the sensitiveness of the fish species dab (Limanda limanda), plaice (Pleuronectes platessa) and cod (Gadus morhua) immediately after catch and after different duration of bulk storage were carried out on board the fishing research vessel “Solea”. The aim of the investigations was to get an idea wether or not the central nervous system of the fishes was in function and the fishes could suffer pain. The proportion of sensitive dab, plaice and cod immediately after the catch was higher than 70, 80 and 95 %, respectively. After 30 min of bulk storage the percentage was reduced to 50, 60 and 70 % resp., after 90 minutes to 5, 15 % and 35 %. In cod it decreased further to 5 % after 120 min. An influence of trawling time (0,5 - 2 h) or size of the catch (100 to 1000 kg) on the number of sensitive animals was not found. Although fishing parameters in commercial fishery will in most cases put a stronger mechanical stress on the animals during trawling and handling on board a certain number of sensitive fish can still be expected.

Methode zur Bestimmung des Sandgehalts in Muschelerzeugnissen

A method to estimate the sand content in mussel products is described. It is based on the § 35 method for measuring the hydrochloric acid-insoluble portion of tomato purée, modified by freeze-drying of the sample during the preparation. By increasing of the volume of the sample it is also possible to minimise the standard deviation and the coefficient of variation.

EU-Aktion zur Verbesserung der wissenschaftlichen Basis für Bestandsabschätzungen und -vorhersagen

Im Rahmen der Bewirtschaftung der Fischressourcen des Nordatlantiks werden für alle Nutzfischarten jährlich Bestandsgrößen und Nachwuchsraten erarbeitet, die Grundlagen für die Festlegung künftiger Fangmengen dieser Arten sind. Da in diese Berechnungen Daten Unterschiedlicher Zuverlässigkeit eingehen und den Berechnungsmethoden verschiedene Voraussetzungen zugrunde liegen, bestehen Unsicherheiten in der Präzision der Vorhersagen. Deshalb werden die benutzten Modelle und ihre Ergebnisse laufend kritisch überprüft und weiterentwickelt. Aufgrund der Einschränkungen der bisher benutzten Methoden und den Wünschen der Fischwirtschaft, Vorhersagen für Bestandsentwicklungen für mindestens 5 Jahre zu entwickeln, startete einer Reihe europäischer Fischerei- bzw. Meeresforschungsinstitute eine gemeinsame Aktion mit dem Ziel, die wissenschaftliche Basis für Bestandsabschätzungen und -vorhersagen zu verbessern. Diese "ConcertedAction: Sustainable fisheries. How can the scientific basis for fish stock assessments and predictions be improved? (SAP)" wird vom Generaldirektor für Fischerei der Kommission der Europäischen Gemeinschaft als Projekt FAIR CT 97-3805 seit dem 01.01.1998 für 40 Monate gefördert.

Fangtechnische Untersuchungen zur Aal- und Plattfischfischerei in der Ostsee

Seit 1996 werden im Institut für Fischereitechnik (IFH) fangtechnische Untersuchungen zwecks Reduzierung des Beifangs bei der stark discardbelasteten Aalschleppnetzfischerei in der Ostsee durchgeführt. Diese Arbeiten wurden in Zusammenarbeit mit dem Institut für Fischerei der Landesforschungsanstalt für Landwirtschaft und Fischerei Mecklenburg-Vorpommern sowie dem Verein MARITEC e. V. durchgeführt (Gabriel und Thiele 1997; Gabriel et al. 1998). Nach Auswertung der bisher vorliegenden Ergebnisse und nach einer weiterführenden Beifanganalyse zur Schleppnetzfischerei auf Grundfischarten, insbesondere Plattfisch, in den Küstengewässern Mecklenburg-Vorpommerns wurden 1998 folgende technische Untersuchungen vorgesehen: • Überprüfung einer kombinierten Fischerei mit Plattfisch-Grundschleppnetzen und passiven Aalfanggeräten (Körbe, Langleinen, Korbketten) • Erprobung einer neuen Steertkonstruktion im Plattfischfang auf verbesserte Selektionseigenschaften • Blankaalfang mit einern pelagischen Tucknetz • Versuche in der passiven Fischerei mit verbesserten bzw. neuartigen Aalfanggeräten

Weitere Untersuchungen zur Selektion des Ostseedorsches mit neuartigen Steertkonstruktionen

Trotz der 1993 getroffenen Entscheidung der Internationalen Ostseefischereikommission, die Steertmaschenmindestöffnung von 105 auf 120 mm zu erhöhen, hat sich die allgemeine Situation der Dorschbestände in der zentralen Ostsee (Ernst 1998) bisher nicht verbessert. Man muß daher fragen, warum bisher keine wirksamen technischen Maßnahmen zum Schutz der Jungfische eingeführt und durchgesetzt worden sind. Die Entscheidung zur Einführung einer erhöhten Steertmaschenöffnung wurde 1993 bereits durch Einsprüche der Praxis relativiert. Es wurde von der Fischereipraxis verlangt, alternative Steertkonstruktionen zuzulassen, die es gestatten würden, die mit einem Steertwechsel verbundene Kosten zu minimieren. Dem war mit der Maßgabe zugestimmt worden, daß für solche alternativen Steerte der Nachweis geführt wird, daß mindestens 50 % der Dorsche von 38 cm Länge noch entkommen können. Zwei neuartige Steertformen, die sogenannte "schwedische" und die "dänische" (Dahm und Thiele 1996), wurden dann - allerdings ohne solchen gesicherten Nachweis - in das Regelwerk der Ostseefischereikommission aufgenommen und als zulässig erklärt.

Untersuchungen zur Langleinenfischerei auf Dorsch und Aal in der Ostsee

With the aim to reduce bycatches and discards first investigations were carried out in longlining for cod and eel in the Baltic. In the case of eel fisheries they are compared with small mesh size trawling and in the case of cod fisheries with gillnetting, where during the winter season unwished bycatches of seabirds could be a problem. First results show that these investigations should be continued.

Anwendungsmöglichkeiten instrumenteller Texturanalyse zur Charakterisierung industriell hergestellter Farcen

Commercially processed and for industrial purpose destined minces of several fish species were characterised with regard to their texture using texture profile analysis (TPA) of boiled specimen and by measuring the penetration force on raw minces as well as with regard to their colour by instrumental measurements of CIELab values. Concerning the parameters investigated the minces were in most cases significantly different. It was evident that the fish species is responsible for the functional properties of these intermediate products. For the TPA the influence of the measurement conditions was demonstrated and an appropriate method derived. IEF of proteins was used to verify the declared fish species. Unfortunately, this was not possible in all cases due to the lack of comparable pattern. Both the DMA and FA content were found to be in the normal range except those for saithe.

Neue Erkenntnisse zur Verteilung des Nordseeherings auf die Gebiete der EU und Norwegens

A study by K.R. Patterson of the Marine Lab, Aberdeen, Scottland, presented to the EU comission in June 1997, investigated the distribution of Herring in the North Sea, i. e. the zonal attachment of the stock to EU and Norwegian waters, respectively. Evaluation of data from the ICES International Bottom Trawl Surveys and Herring Acoustic Surveys conducted in the last 10 years showed a wide variation in biomass and zonal attachment, depending on the type of survey used and the season sampled. However, a mean share of 16 % was estimated to be attached to the Norwegian waters . In contrast to earlier analyses based on commercial catches there is little support that this proportion increases with increasing stock size. It is expected that this study will give rise to some discussion on the forthcoming EU-Norwegian consultations on North Sea herring.

Zur Fang- und Bestandssituation von Hering und Sprott in der Ostsee

Information is given on the landings of herring and sprat in the Skagerrak/Kattegat and Baltic Sea. Based on assessment units used by the ‘Herring Assessment Working Group for the Area South of 62° N’ and the ‘Baltic Fisheries Assessment’ working group, the total landings are shown for the years 1974 to 1996. Further the quarterly landings for 1996 are listed on national basis by area/Sub-Division. In addition an actual description of the national fleets operating in the Skagerrak/Kattegat and Baltic Sea is given. At least the actual stock development and the catch options estimated by the corresponding working groups for different assessment units is presented.

Zur Bedeutung des Größenunterschieds weiblicher und männlicher Nordseegarnelen für die kommerzielle Garnelenfischerei

Aiming at a better knowledge on the distribution and fecundity of hibernating Crangon crangon (L.), the R.V. "Solea" in January is sampling shrimps in the German Bight since 1991. A total of 3.000 shrimps (1.608 females and 1.392 males) have been investigated with regard to total length, to the width of the carapace and to spawning activity.

Technische Maßnahmen zur Schonung des Ostseedorschs - Gegenwärtige Ergebnisse der Selektionsforschung

Die gegenwärtige Situation der westlichen und östlichen Dorschbestände in der Ostsee wird von den Experten des Internationalen Rates für Meeresforschung, verglichen mit den 80er Jahren, als ungünstig beurteilt. Noch 1994 wurde daher kein Anlaß gesehen, trotz massiver Proteste der Praxis, die Empfehlung für eine moderate Befischung aufzuheben (Anon. 1994).