Identifizierung der Welsart in Filetware durch Protein- und DNA-Analyse

Zusammenfassung Zur Identifizierung der folgenden vier Welsarten bzw. zwei Hybriden (Clarias gariepinus, Pangasius hypophthalmus, Pseudoplatystoma spp., Silurus glanis, Claresse® und Melander®) wurden die isolektrische Fokussierung (IEF) der wasserlöslichen Muskelproteine und die Polymerase-Kettenreaktion (PCR) zur Vervielfältigung und Sequenzierung eines Abschnittes aus dem Cytochrom b – Gen eingesetzt. Die IEF ergab artspezifische Proteinmuster mit hitzestabilen Proteinbanden im anodalen Gelbereich. Der afrikanische Wels (C. gariepinus) und das Hybriderzeugnis Melander® wiesen das gleiche Proteinmuster auf. Mittels DNA-Analyse ließen sich die Welsarten anhand ihrer Cytochrom b Gensequenzen eindeutig identifizieren. Auch hier zeigte der Welshybrid Melander® ein identisches Ergebnis wie der afrikanische Wels. Die Schwierigkeiten der Identifizierung von Tigerwelsen südamerikanischer Herkunft aus der Gattung Pseudoplatystoma werden diskutiert. Abstract Isoelectric focusing (IEF) of water soluble proteins and PCR-based DNA- analysis were used to differentiate between four catfish species (Clarias gariepinus, Pangasius hypophthalmus, Pseudoplatystoma spp., Silurus glanis) and two hybrids Claresse® and Melander®. Specific protein patterns have been obtained for all species and Claresse®, but in case of Melander® the identical pattern was observed as for the African catfish Clarias gariepinus. By sequencing the PCR products and application of BLAST, authenticity of the different catfish samples was confirmed. The cytochrome b gene sequences of Melander® and African catfish were identical. The difficulties of identifying catfishes of the genus Pseudoplatystoma are discussed.

Die Entwicklung des Aufwandes in der deutschen Garnelenfischerei und der Versuch einer Standardisierung der jährlichen Einheitsanlandungen (LPUE) zwischen 1976 und 2010

Brown shrimp is a fastgrowing, shortlived species, and all attempts to use stock assessment methodologies typically applied to other fisheries are usually unsuccessful. Here landings per unit effort data (LPUE) for the German fleet based on a number of effort metrics are used as indices of stock size. Their utility in relation to describing stock development and fisheries management is discussed. LPUE estimates indicate that stock sizes between 1976 and 1989 were relatively stable. In 1990, the lowest reported landings of brown shrimps in Germany coincided with severe economic problems for the shrimp fisheries. From 1990 to 2010 standardised annual indices show that both landings and LPUE estimates have increased at variable rates suggesting large stocks of brown shrimps in recent years. This is discussed in relation to the positive effects of reduced predator abundance and favourable climatic factors.

Differenzierung von Kammmuscheln durch DNA-Analyse

Abstract In the last years scallops have reached a considerable popularity and the import of scallops into the EU has increased about 20 % over the last fi ve years from some 50.000 t to nearly 63.000 t in the year 2010. Scallops are fi shed or farmed, and traded as fresh or deep frozen product. Recently investigation of scallop products of various origins by determining the species using molecular biological techniques showed that the species had been mislabelled in a considerable proportion of samples. Determination of the species was performed by PCR-based DNA-analysis of mitochondrial DNA followed by (i) sequencing the PCR product and (ii) comparison of the DNA sequence with entries in GenBank using BLAST. The deduced sequences of the analysed samples were considerably different from each other allowing the unambiguous assignment of samples to a certain species. Kurzfassung Die Nachfrage von Kammmuscheln in der EU hat in den letzten fünf Jahren erheblich zugenommen. Der Import stieg von knapp 53.000 t im Jahr 2005 um 20% auf annähernd 63.000 t im Jahr 2010. Gehandelt werden Kammmuscheln sowohl als frische als auch als Tiefkühlware aus Wildfängen und Aquakultur. Untersuchungen von Kammmuschel-Proben aus verschiedenen Ursprungsländern und Bestimmung der Spezies auf molekularbiologischer Basis zeigten, dass ein erheblicher Anteil der Proben falsch deklariert war. Die Bestimmung der Spezies erfolgte durch Vervielfältigung eines Abschnitts des 16S rRNA Gens durch Polymerase- Kettenreaktion (PCR), anschließender Sequenzanalyse der PCR-Produkte und Vergleich der DNA Sequenzen untereinander und mit Dateneintragungen in GenBank. Die DNA-Sequenzen der ermittelten Abschnitte der 16S rRNA der Proben unterschieden sich erheblich voneinander und erlaubten eine eindeutige Zuordnung zu jeweils einer Spezies.

German Eel Model (GEM II) for describing eel, Anguilla anguilla (L.), stock dynamics in the river Elbe system

The eel, Anguilla anguilla (L.), stock of the river Elbe severely decreased during the last decades. Detailed knowledge of the stock dynamics in freshwater and especially of the impact factors is necessary to take effective measures for stock conservation and improvement. The dynamics of the eel stock are modelled based on immigration, stocking, natural mortality and mortalities caused by fishing, angling, cormorants and hydropower plants. The model estimates the number of emigrating eel. Moreover, it enables to study the sensitivity of the estimates related to the uncertainty of the source data of the different influencing factors. The model may be used to develop management strategies and to assess the effi ciency of different management options. Zusammenfassung Der Aalbestand im Elbesystem ist in den letzten Jahrzehnten stark zur

Ungewohnliche Gewichsabnahme von Dorsch im 2. Jahresquartal in Bornholm Becken (ICES-Gebeit 25) und der Arkonasee (ICES-Gebiet 24)

Cod captured by commercial fi shery in the Bornholm Basin in quarter 2 of 2001 were not suitable for the mechanical processing due to low condition and weight. The absolute mean weight of cod captured by the commercial fishery in the Arkona Sea and Bornholm Basin in the same quarter during the last fi ve years was studied to describe its development. The results of a GLM (Generalized Linear Model) analysis showed similar development of body weight in the Bornholm Basin and in the Arkona Sea between 2007 and 2011. The mean weight of cod in the Bornholm Basin increased from 2007 to 2008 in both areas followed by a relative stable weight until 2009 and a decrease until 2011. In the Arkona Sea the mean weight of cod 2009 has decreased in comparison to 2008, then have increased 2010 slightly and last have decreased in 2011. The analyses showed that the weight of cod is signifi cantly infl uenced by length, age and maturity of individuals.

Die vertikale Verteilung von Heringslarven im Greifswalder Bodden

Kurzfassung Im Rahmen einer Bachelorarbeit wurde untersucht, ob die Larven des frühjahrslaichenden Herings der westlichen Ostsee im Greifswalder Bodden eine inhomogene vertikale Verteilung aufweisen, da in bisherigen Studien aufgrund der niedrigen Gewässertiefe des Boddens von hydrografischer Durchmischung und somit homogener Ichthyoplanktonverteilung ausgegangen wurde. Dazu wurden zwei Nullhypothesen überprüft, eine, die annimmt, dass Heringslarven allgemein im Greifswalder Bodden homogen verteilt sind, eine zweite, nach der auch verschiedenen Längenklassen der Heringe homogen verteilt sind. Die Proben, die Mitte April an drei verschiedenen Stationen im Greifswalder Bodden genommen wurden, zeigten signifikante Unterschiede der Larvenabundanzen allgemein zwischen den beprobten Tiefenstufen als auch der Längenklassen zwischen den Tiefenstufen, sodass beide Nullhypothesen abzulehnen sind. Eine homogene Verteilung der Heringslarven kann ausgeschlossen werden. Abstract Larvae of the Western Baltic Spring Spawning Herring were sampled in the Greifswalder Bodden in the course of a Bachelor Thesis to investigate whether they are inhomogeneously vertically distributed. Previous research assumed homogeneous vertical distribution because of the shallowness of the Greifswalder Bodden due to hydrographical mixing of the water and the ichthyoplankton. Two null hypotheses were tested, one which presumes even vertical distribution of the herring larvae and another which presumes even vertical distribution within different length classes in the Greifswalder Bodden. Sampling took place at three different stations in the Greifswalder Bodden during April and results showed significant differences of the larvae abundances between the sampled depths and also significant differences of the length classes between the sampled depths. Therefore both null hypotheses can be rejected and a homogeneous vertical distribution of the herring larvae in the Greifswalder Bodden can be excluded.

Bericht über vergleichende Untersuchungen zur Lagerung von Fischfilet in konventionellen und mit Silbernanopartikeln beaufschlagten Verpackungen

Kurzfassung Die Lebensmittelbranche erwartet durch den Einsatz von Nanotechnologien hervorragende Fortschritte bei der Verbesserung der Produktqualität und der Lebensmittelsicherheit. Vor diesem Hintergrund wurde 2009 am Max Rubner Institut der Fach- und Institutsübergreifende Forschungsschwerpunkt „Nanotechnologie“ etabliert, um Grundlagen zu erarbeiten, aufgrund derer die Auswirkungen der Nanotechnologie auf Lebensmittel und damit die Ernährung und Gesundheit der Verbraucher beurteilt werden können. In diesem Forschungsprojekt wurde der Einfluss neuer, mit Nanopartikeln beaufschlagter Verpackungsfolien auf Fischfilet untersucht. Abstract: The food industry expects by the application of nanotechnology excellent progress in the improvement of the product quality and the food safety. On this background the Max Rubner Institute established in 2009 an interdisciplinary focus on nanotecchnology research to formulate principles upon which the impact of nanotechnology on food and thus the nutrition and health of consumers can be assessed. In this research, the impact of new, nanoparticles containing packaging films was examined for fish fillet.

Versuche zur Verringerung des Dorschbeifanges in Grundschleppnetzen

Bottom otter trawls with cut back upper panels were tested in the fischeries on Baltic Sea flounder and North Sea plaice to reduce cod by-catch. In a first series of experiments on board the fishing research cutter “Clupea” the cod-bycatch was reduced by 63 %. The catch of flounder was by 92 % higher in the cut back trawl. The same trawl with the same experimental set-up achieved aboard the fisching research vessel “Solea” on the other hand a reduction in cod-bycatch by 69 %. The catch of flounder was 23,3 % lesser in the topless trawl, which was in contrast to the “Clupea” trials. In the second series of experiments with the same cut back trawl the splits were shortened to reduce the net opening height from 0,9 m to 0,6 m previously. The cod-bycatch was reduced by 86 % and the catch of flounder was 81 % higher in comparison to the complete trawl. A prototype made of stronger net material but based on the cutting and rigging design of the tested cut back trawl with the shortened splits was tested with commercial twin trawlers. The cod-bycatch was reduced by 82,2 %, the catch of plaice by 43,3 % and the catch of dab by 44,6 % in the comparison to the commercial used trawl TV280. The flounder catch was in the topless trawl 10 % higher. In the North Sea in the comparison to a bottom trawl TV300 the cod by-catch was reduced by 89,8 %, but the catch of plaice and dab were 54 % and 58,7 % lesser. In the next step was a prototype of a normally in the North Sea plaice fisheries used trawl tested with a cut back of 2 m only. The cod catch was reduced by 16,9 % but the plaice catch, however , by 22,3 %. Kurzfassung Schleppnetze mit verkürzten Oberblättern wurden in der Fischerei auf Ostseeflunder und Nordseescholle zur Verringerung des Dorschbeifanges erprobt. In einer ersten Versuchsserie mit dem Forschungskutter „Clupea“ wurde der Dorschbeifang um 63 % reduziert. Die Fänge der Zielart Flunder waren im reduzierten Schleppnetz dagegen um 92 % höher. Das gleiche Schleppnetz mit gleichem Versuchsaufbau erzielte auf dem Fischereiforschungsschiff „Solea“ dagegen eine Reduktion des Dorschbeifanges um 69 %, wobei im Gegensatz zu den „Clupea“-Versuchen der Flunderfang um 23,3 % im reduzierten Netz geringer war. In der zweiten Versuchsserie wurden die Netzstander am reduzierten Schleppnetz verkürzt, um die Netzöffnungshöhe zu verringern. Dadurch wurde der Dorschbeifang in Versuchen mit dem Forschungskutter „Clupea“ um 86 % verringert und die Flunderfänge waren im reduzierten Schleppnetz 81 % höher. Basierend auf dem Zuschnitt des erprobten Schleppnetzes, jedoch aus stärkerem Netzmaterial gefertigt, wurde ein Prototyp auf kommerziellen Doppelnetz-Kuttern erprobt. In der Ostsee wurde in diesen Versuchen der Dorschbeifang um 82,2 %, der Schollenfang um 43,3 % und der Klieschenfang um 44,6 % mit dem im Oberblatt verkürztem Schleppnetz im Vergleich zum Kutterschleppnetz TV280 reduziert. Der Flunderfang war im reduzierten Schleppnetz 10 % höher. Auf der Nordsee wurde mit diesem Versuchsnetz im Vergleich zu einem TV 300 der Kabeljaubeifang um 89,8 % verringert, die Schollenfänge waren jedoch 54 % geringer und die Klieschenfänge 58,7 % geringer als im Vergleichsnetz. In einer weiteren Variante wurde ein in der Nordseeschollenfischerei verwendetes Grundschleppnetz mit 2 m geringfügig im Oberblatt zurückgeschnitten und mit dem Prototyp auf einem Doppelnetz-Heckschlepper verglichen. Der Kabeljaubeifang wurde dadurch um 16,9 % der Schollenfang aber um 22,3 % verringert

Beschreibung des aktuellen Verlaufes der jährlichen Reifeentwicklung und der Laichaktivitäten von Dorschen in der Arkonasee (ICES SD 24)

Abstract The spawning activities of cod were described in the Arkona Sea from 2009 to 2012 and were compared with estimates of the period 1992 – 1999. Cod spawned mainly from beginning of June till the middle of July every year. In the same period spawning was observed in the Bornholm Sea. The spawning activities in July were limited by water temperature above the critical limits. Spawning activities in spring which were observed in the 90 ties were of lower importance between 2009 and 2012. Higher proportions of spent cod were observed in the Arkona Sea in August and autumn between 2009 and 2012 compared to the earlier period, indicating immigration of cod from the Bornholm Sea after spawning. The study showed that higher proportion of cod with developing sex products were observed in the Arkona Sea between 2009 and 2012 compared to the 90 ties. Kurzfassung Die Laichaktivitäten der Dorsche in der Arkonasee werden für den Zeitraum 2009 – 2012 dargestellt und im Vergleich mit dem Zeitraum 1992 – 1999 diskutiert. Die Hauptlaichaktivitäten haben im Untersuchungszeitraum von Anfang Juni bis Mitte Juli stattgefunden und lagen damit in ihrem jahreszeitlichen Verlauf innerhalb der Zeitperiode der Laichaktivitäten in der angrenzenden Bornholmsee. In der Arkonasee wurden jeweils im Juli diese Ereignisse durch ansteigende Wassertemperaturenbegrenzt. Die, noch in den 90-er Jahren beobachteten, Laichaktivitäten im Frühjahr haben aktuell an Bedeutung verloren. Im Spätsommer und Herbst war ein, im Vergleich zu den 90-er Jahren, höherer Anteil an abgelaichten Tieren in der Arkonasee zu beobachten, der als Indiz für eine Zuwanderung von abgelaichten Dorschen aus der Bornholmsee gewertet wird. Insgesamt hat der Anteil an Tieren mit sich entwickelnden Geschlechtsprodukten (aktive Laicher) im Untersuchungszeitraum, im Vergleich zu den 90-er Jahren, zugenommen.

PCR-SSCP and Isoelectric Focusing as Screening Methods for Identification of (Sub-) Tropical Fish Species

To ensure the authentication of fishery products lacking biological characters, rapid species identification methods are required. Two DNA- and protein-based methods, PCR-SSCP (polymerase chain reaction - single strand conformation polymorphism) of a 464 bp segment of the cytochrome b – gene and isoelectric focusing (IEF) of water-soluble proteins from fish fillets, were applied to identify fillets of (sub-) tropical fish species available on the European market. Among the samples analysed were two taxonomically identified species from the family Sciaenidae and one from Sphyraenidae. By comparison of DNA- and protein patterns of different samples, information about intra-species variability of patterns, and homogeneity of batches (e.g. fillet blocks or bags) can be obtained. PCR-SSCP and IEF may be useful for pre-checking of a large number of samples by food control laboratories. Zusammenfassung Zur Sicherstellung der Authentizität von Fischerei-Erzeugnissen ohne biologische Merkmale sind schnelle Verfahren zur Speziesidentifizierung hilfreich. Zwei Methoden der DNA- bzw. Protein-Analyse wurden eingesetzt, um Filets (sub-) tropischer Fischarten, die auf dem europäischen Markt angeboten werden, zu identifizieren. Bei diesen Methoden handelt es sich um die PCR-SSCP (Polymerase-Kettenreaktion – Einzelstrang-Konformationspolymorphismus) – Analyse der PCR-Produkte und die IEF (isoelektrische Fokussierung) der wasserlöslichen Fischmuskelproteine. Unter den untersuchten Proben waren zwei taxonomisch bestimmte Arten aus der Familie Sciaenidae und eine Spezies aus der Familie Sphyraenidae. Durch Vergleich der DNA- bzw. Proteinmuster lassen sich Informationen über die intra-spezifische Variabilität solcher Muster und die Einheitlichkeit von Partien (beispielsweise Filetblöcke oder Filetbeutel) gewinnen. PCR-SSCP und IEF können in Laboratorien der Lebensmittelüberwachung als Vortest gerade bei hohen Probenzahlen sinnvoll eingesetzt werden.

Preliminary estimation of growth in Cheimerius nufar (Sparidae) from southern Mozambique

On the basis of length-frequency data collected in 1987, by the hook-and-line fishery research program, preliminary estimates of the parameters of a seasonally oscillating version of the von Bertalanffy equation for Cheimerius nufar (Ehrenberg, 1830) were obtained, i.e., TL∞=70 cm and K=0.17 yearˉ¹. A discussion of these results is provided.

Wetlands and riparian zones as buffers and critical habitats for biotic communities in Lake Victoria

Despite their ecological and socio-economic importance, Lake Victoria's adjoining "swamps" and lake interface are among the least investigated parts of the lake. The "swamps" a term commonly equated to "wastelands" and the difficult working environment they present in comparison to open water, are major factors for the low level of attention accorded to shoreline wetlands. Moreover, definitions of wetlands highlighted for example in the Ramsar Convention as "areas of marsh, fern, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh or brackish, or salt, including areas of marine water, the depth of which does not exceed six metres" (Ramsar, 1971) were designed to protect birds (water fowl) of international importance. The Ramsar definition, which also includes oceans, has till recently been of limited use for Lake Victoria, because itdoes not fully recognise wetlands in relation to other public concerns such as water quality, biodiversity and the tisheries that are of higher socioeconomic priority than waterfowl. Prior to 1992, fishery research on Lake Victoria included studies of inshore shallow habitats of the lake without specific reference to distance or the type of vegetation at the shore. Results of these studies also conveniently relied heavily on trawl and gill net data from the 5-10 m depth zones as the defining boundary of shallow inshore habitats. In Lake Victoria, such a depth range can be at least one kilometre from the lake interface and by the 10m depth contour, habitats are in the sub-littoral range. Findings from these studies could thus not be used to make direct inferences on the then assumed importance of Lake Victoria wetlands in general.

A note on some parasites of Merluccius capensis (Pisces) and their zoogeographical significance

During the Southeastern Atlantic Expedition of the German fishery research vessel "Walther Herwig" in 1967 the main emphasis lay on selective fishing of the South African hake Merluccius capensis (von BRANDT 1967). Some of the fish were found to be infested by ecto-and endoparasites both of which were collected whenever possible. Large plerocercoids of Dibothriorhynchus grossum whose adult stage lives in the South Atlantic Ocean in Lamna cornubica (L.SZIDAT, personal communication) were quite common as were cysticercoids of a Tetrarhynchus sp., which had also been reported in Cynoscion striatus off the Argentinian coast (MACDONAGH 1927, cited in Szidat, personal communication). Brownish nematodes were infesting the ovaries of several fish, but could not be identified. The most common ectoparasite to be observed was the parasitic isopod Livoneca raynaudii (fam. Cymothoidae) whose early larval stages were also found.

The status of shark and ray fishery resources in the Gulf of California: applied research to improve management and conservation

Seasonal surveys were conducted during 1998–1999 in Baja California, Baja California Sur, Sonora, and Sinaloa to determine the extent and activities of artisanal elasmobranch fisheries in the Gulf of California. One hundred and forty–seven fishing sites, or camps, were documented, the majority of which (n = 83) were located in Baja California Sur. Among camps with adequate fisheries information, the great majority (85.7%) targeted elasmobranchs during some part of the year. Most small, demersal sharks and rays were landed in mixed species fisheries that also targeted demersal teleosts, but large sharks were usually targeted in directed drift gillnet or, to a lesser extent, surface longline fisheries. Artisanal fishermen were highly opportunistic, and temporally switched targets depending on the local productivity of teleost, invertebrate, and elasmobranch fishery resources. Major fisheries for small sharks (< 1.5 m, “cazón”) were documented in Baja California during spring, in Sonora during autumn–spring, and in Sinaloa during winter and spring. Triakid sharks (Mustelus spp.) dominated cazón landings in the northern states, whereas juvenile scalloped hammerheads (Sphyrna lewini) primarily supported the fishery in Sinaloa. Large sharks (> 1.5 m, “tiburón”) were minor components of artisanal elasmobranch fisheries in Sonora and Sinaloa, but were commonly targeted during summer and early autumn in Baja California and Baja California Sur. The pelagic thresher shark (Alopias pelagicus) and silky shark (Carcharhinus falciformis) were most commonly landed in Baja California, whereas a diverse assemblage of pelagic and large coastal sharks was noted among Baja California Sur landings. Rays dominated summer landings in Baja California and Sinaloa, when elevated catch rates of the shovelnose guitarfish (Rhinobatos productus, 13.2 individuals/vessel/trip) and golden cownose ray (Rhinoptera steindachneri, 11.1 individuals/vesse/trip) primarily supported the respective fisheries. The Sonoran artisanal elasmobranch fishery was the most expansive recorded during this study, and rays (especially R. productus) dominated spring and summer landings in this state. Seasonal catch rates of small demersal sharks and rays were considerably greater in Sonora than in other surveyed states. Many tiburón populations (e.g., C. leucas, C. limbatus, C. obscurus, Galeocerdo cuvier) have likely been overfished, possibly shifting effort towards coastal populations of cazón and rays. Management recommendations, including conducting demographic analyses using available life history data, determining and protecting nursery areas, and enacting seasonal closures in areas of elasmobranch aggregation (e.g., reproduction, feeding), are proposed. Without effective, enforceable management to sustain or rebuild targeted elasmobranch populations in the Gulf of California, collapse of many fisheries is a likely outcome. (PDF contains 243 pages)