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.

Estimated ages of red porgy (Pagrus pagrus) from fishery-dependent and fishery-independent data and a comparison of growth parameters

The red porgy, Pagrus pagrus, is an important reef fish in several offshore fisheries along the southeastern United States. We examined samples from North Carolina through southeast Florida from recreational (headboat) and commercial (hook and line) fisheries, as well as samples from a fishery-independent source. Red porgy attain a maximum age of at least 18 years and 733 mm total length. The weight-length relationship is represented by the ln-ln transformed equation: W = 8.85 × 10–6(L)3.06, where W = whole weight in grams, and L = total length in mm. The von Bertalanffy growth equation fitted to the most recent, back-calculated lengths from all the samples is Lt = 644(1 – e –0.15(t + 0.76)). Our study revealed a difference in mean length at age of red porgy from the three sources. Red porgy in fishery-independent collections were smaller at age than specimens examined from fishery-dependent sources. The difference in length-at-age may be related to gear selectivity and have important consequences in the assessment of fish stocks.

Growth parameters of Lepturacanthus savala (Cuvier, 1829) from Mumbai waters

Lepturacanthus savala (Cuvier, 1829) constitutes a minor fishery contributing 23.3% to the total ribbonfish catch in Maharashtra. Based on the length data obtained from shrimp trawlers and the traditionally operated bag nets, age and growth of the species have been investigated from Mumbai waters. Growth was studied by various computer-based methods incorporated in FiSAT Programme. The growth parameters L∞ and K (on annual basis) by Gulland-Holt plot were 683.3 mm and 0.87, respectively. As the seasonal temperature variations in coastal waters of Mumbai are not pronounced, the seasonally oscillating growth patterns by ELEFAN and Appledoorn's method were not considered. Following the von Bertalanffy growth model, the fish attains 399.8, 567.2 and 637.4 mm at the end of 1, 2 and 3 years, respectively, and the lifespan of the fish is about 3.3 years.