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.

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

Cannibalism in Japanese flounder juveniles, Paralichthys olivaceus, reared under controlled conditions

Laboratory experiments were conducted to determine the effects of sand substratum, light, starvation, fish density and size variation on cannibalism among Japanese flounder juveniles, Paralichthys olivaceus. Cannibalistic behavior (biting and swallowing) increased significantly with starvation except in darkness, where juveniles could not find and attack their prey. Cannibalism occurred more frequently in heterogeneous than in the homogeneous size groups. Cannibalism was more frequent in light than in darkness at each starvation level. With sufficient food present, sand had no significant effect on cannibalism among homogeneous size juveniles, but played an important role in discouraging predation among members of the heterogeneous size groups. With sufficient food present, the rate of cannibalism was generally low and there were no significant differences in cannibalism among fish density levels of the homogeneous juveniles, With starvation, the cannibalism rate was significantly higher in high density groups than in the lower ones. Our results indicate that size variation, starvation and Light are the major factors affecting cannibalism in flounder juveniles, while sand and fish density only have a limited effect on cannibalism, depending on the nature of other factors. (C) 2000 Elsevier Science B.V. All rights reserved.

Experiments and observations made at the Plymouth Laboratory

Diagnostic characters in flat fishes. Development of the egg in flat fishes & pipe fishes. A piebald plaice. Growth & distribution of young food-fishes. Notes on rare or interesting specimens.

Fish migrations in the Barents Sea

Results of marking of haddock, pollack, Greenland halibut, plaice, and blue sea cat are discussed. Their seasonal migrations underwent drastic changes between the 1930s and 1960s to 1970s after cooling in the Barents Sea.

Principles of the contact lens /

Includes index.

Report of the Workshop on Growth-increment Chronologies in Marine Fish: climate-ecosystem interactions in the North Atlantic 2 (WKGIC2). 18-22 April 2016 Esporles, Mallorca, Spain

Over the past several decades, thousands of otoliths, bivalve shells, and scales have been collected for the purposes of age determination and remain archived in European and North American fisheries laboratories. Advances in digital imaging and computer software combined with techniques developed by tree-ring scientists provide a means by which to extract additional levels of information in these calcified structures and generate annually resolved (one value per year), multidecadal time-series of population-level growth anomalies. Chemical and isotopic properties may also be extracted to provide additional information regarding the environmental conditions these organisms experienced.Given that they are exactly placed in time, chronologies can be directly compared to instrumental climate records, chronologies from other regions or species, or time-seriesof other biological phenomena. In this way, chronologies may be used to reconstruct historical ranges of environmental variability, identify climatic drivers of growth, establish linkages within and among species, and generate ecosystem-level indicators. Following the first workshop in Hamburg, Germany, in December 2014, the second workshop on Growth increment Chronologies in Marine Fish: climate-ecosystem interactions in the North Atlantic (WKGIC2) met at the Mediterranean Institute for Advanced Studies headquarters in Esporles, Spain, on 18–22 April 2016, chaired by Bryan Black (USA) and Christoph Stransky (Germany).Thirty-six participants from fifteen different countries attended. Objectives were to i) review the applications of chronologies developed from growth-increment widths in the hard parts (otoliths, shells, scales) of marine fish and bivalve species ii) review the fundamentals of crossdating and chronology development, iii) discuss assumptions and limitations of these approaches, iv) measure otolith growth-increment widths in image analysis software, v) learn software to statistically check increment dating accuracy, vi) generate a growth increment chronology and relate it to climate indices, and vii) initiate cooperative projects or training exercises to commence after the workshop.The workshop began with an overview of tree-ring techniques of chronology development, including a hands-on exercise in cross dating. Next, we discussed the applications of fish and bivalve biochronologies and the range of issues that could be addressed. We then reviewed key assumptions and limitations, especially those associated with short-lived species for which there are numerous and extensive otolith archives in European fisheries labs. Next, participants were provided with images of European plaice otoliths from the North Sea and taught to measure increment widths in image analysis software. Upon completion of measurements, techniques of chronology development were discussed and contrasted to those that have been applied for long-lived species. Plaice growth time-series were then related to environmental variability using the KNMI Climate Explorer. Finally, potential future collaborations and funding opportunities were discussed, and there was a clear desire to meet again to compare various statistical techniques for chronology development using a range existing fish, bivalve, and tree growth-increment datasets. Overall, we hope to increase the use of these techniques, and over the long term, develop networks of biochronologies for integrative analyses of ecosystem functioning and relationships to long-term climate variability and fishing pressure.