Description: Commercially exploited stocks that have experienced declines in population abundance have responded by altering life history traits of growth and maturation. Cod is not only becoming mature at an earlier age but also, the majority of the stock comprises fishes with no previous spawning experience. Actual fisheries management does not take in account qualitative differences within the spawning stock. If the stock responds to continued exploitation by shifting maturity to an earlier stage, fish will spawn at smaller sizes. They will produce smaller eggs, and consequently small and less viable larvae, so that the contribution to the spawning stock biomass will be less than expected. There are many advantages for delaying maturation: Larger and heavier fish will be better conditioned for spawning, have higher fecundity and larger eggs that are more viable. Harvesting at delayed recruitment enables the stock to maintain a larger SSB with an expanded age structure while supporting a sustainable fishery.

Description: Over the past decade large carbonate mound structures, situated in several provinces along the European continental margin have been discovered in 600 to 1200 m water depths. These structures appear as single, conical or ridge-like features, which are often colonised by a deep-water coral ecosystem. Cold-water corals Lophelia pertusa and Madrepora oculata dominate the coral community. Associated sessile and vagile fauna, like sponges, soft corals, bivalves, gastrodpods, crinoids, brachiopods, and fish make these bioherms as diverse as their tropical counterparts. The objective of this study is to reconstruct past environmental settings locked in the sediments of a carbonate mound in the northern Porcupine Seabight, west off Ireland. Detailed investigations were concentrated on seven 3.5 to 6 m long sediment cores, retrieved from Propeller Mound and its closer vicinity. This mound is a ~150 m high structure within the Hovland Mound province, a cluster of several sea-floor protruding carbonate mounds. A first detailed analysis on benthic foraminiferal assemblages in the vicinity of a carbonate mound was performed on two sediment cores, one located on top of the mound and a second one from an off-mound position further north as control site. The off-mound samples reveal two different assemblages: (1) an Interglacial group dominated by infaunal species reflecting present-day environmental and oceanographic conditions with high nutrient flux to the sea-floor and low sediment accumulation under a strong hydrodynamic regime, and (2) a Glacial group, dominated by cassidulinid species, which describe an influence of polar conditions with low nutrient supply and cold intermediate waters. A single species, Elphidium excavatum, dominates the lower core section and is described here as a species displaced from shallow shelf areas. This removal of sediments from the shelf is related to a first advance of the Irish Ice Sheet onto the Irish Mainland shelf, inducing high sedimentation rates of ~28 cm/kyr with a coeval sea-level drop of ~50 m during Late Marine Isotope Stage (MIS) 3. Due to an incomplete stratigraphic record in the on-mound core, the same species of the off-mound assemblages have been grouped in on-mound samples. The results indicate a dominance of the Interglacial group, whereas the Glacial group is less abundant throughout the entire core. This pattern indicates the lack of glacial time intervals in the on-mound core, which is coherent with stable oxygen isotope data and U/Th dates on coral fragments, presenting only interglacial/-stadial values and ages. A third assemblage is abundant in samples of the on-mound core showing elevated epibenthic species not occurring in offmound samples or only to a minor degree. This Mound group shows a great affinity to strong currents, high nutrient availability and is supposed to indicate Mediterranean Outflow Water in the northern Porcupine Seabight, as well as a higher coral cover on Propeller Mound in an earlier interglacial period. A Late Pleistocene decline in mound growth for Propeller Mound is suggested by a decrease of the Mound group towards the Holocene, which might face its complete burial in the future as this already happened to the buried mounds of the Magellan Mound province further north. Detailed information on off-mound sediment structures and contents from visual core description and the interpretation of Computer Tomographic images were used to evaluate sedimentary processes in glacial and interglacial periods. The sediments portray the depositional history of the past ~31 kyr BP, mainly controlled by sea-level fluctuations and the climate regime with the advance and retreat of the Irish Ice Sheet onto the Irish Mainland Shelf. A first advance of glaciers is indicated by a turbiditic release slightly older than 31 kyr BP, coherent with Heinrich event 3. During MIS 3 and MIS 2 shelf erosion prevailed with abundant gravity flows and turbidity currents. A change from glaciomarine to hemipelagic contourite sedimentation during the onset of the Holocene indicates the establishment of the strong, present-day hydrodynamic regime at intermediate depths. A general decrease in sediment accumulation with decreasing distance towards Propeller Mound was discovered throughout the entire core sections. This suggests that currents (turbidity currents, gravity flows, bottom currents) have had a strong impact on sediment accumulation at the mound base for the past ~31 kyr BP. Finally, the reconstructed environmental setting deduced from sedimentary and micropaleontological analyses portrays the boundary conditions of the habitable range for the cold-water coral Lophelia pertusa. The growth of this ecosystem occurs during interglacial and interstadial periods, whereas a glacial retreat of corals is documented in the absence of glacial sediments in the onmound core. These conclusions are summarised in a model – the Mound Factory – which efficiently accounts for the moundd development covering the period of the Northern Hemisphere Glaciation (past 3.1–2.5 Ma).

Description: The present study aimed to know the influence of five phytoplankton species on the feeding behavior, reproduction and survival of the copepod A. tonsa. Biochemical parameters (total lipid, carbohydrate and protein) were measured to know the possible nutritional value of the diet. The species were offered to A tonsa as single and mixed diet. The species used were the flagellates C. acantha and R. baltica, the potentially toxic dinoflagellates A. tamarense and P. lima and the diatom S. costatum. Protein (55-69%) was the major biochemical components per cell volume, following for carbohydrate (17-31%) and lipid (13-18%). The concentration of the biochemical components measured per cell volume influenced the hatching success and survival of the adults. The hatching success was correlated with the egg production and ingestion rate of the copepod and survival of the early stages. No correlation was found between egg production and the biochemical concentration per cell volume. The biochemical components per cell volume showed a high interspecific difference between the species and seemed to better explain part of the nutritional value of the phytoplankton, as the concentrations per dry weight and volume medium. The copepod A tonsa had a selective feeding behavior feeding preferable on S. costatum and R. baltica in the mixed food. The ingestion rate of the specie C. acantha was reduced into the mixed food. The size range of the species offered to A. tonsa did not influence its ingestion rate.The flagellates R. baltica and C. acantha and the mixed food provided the best effects on the reproduction and survival of A. tonsa. The best results among the single foods treatments were found with the alga, with the higher lipid content (R. baltica and C. acantha). The dinoflagellates P. lima all showed eggs production and good hatching but, the survival of adults and early stages was affected. S. costatum prevented egg production. The survival and reproduction of A. tonsa fed on A. tamarense was reduced and comparable to the control (without food). In spite of, no influence was seen when S. costatum, P. lima and A. tamarense were offered mixed with the two flagellates. The mixed food was the best food. This result could demonstrate that the negative effect of these species on the reproduction and survival of A. tonsa was due their insufficient biochemical content as the presence of toxin. A good food muss proved not only a good egg production and hatching success, but a high the survival of the first stages, guaranteed the survival of the organism in the environment. The negative effect of the dinoflagellates on the survival of the early stages of the copepod indicated that these species were a bad food for A. tonsa. Therefore, A. tamarense, S. costatum and P. lima were no a good diet as single food to A. tonsa. The best results with the mixed food could be result from an increase on the levels of DHA, provided for R. baltica, and EPA, provided for S. costatum, also as for the increase of protein supplied for C. acantha, major content of protein per cell volume. But for a better understand of the relation of the biochemical contents with survival e reproduction of aquatic animals makes necessary a analysis of vitamins, minerals and of the constitutes of each gross biochemical composition, such as fatty acids, amino acids, sterols, sugars.

Description: The expedition ARK XIX/3 with the German icebreaking RV "Polarstern" was jointly organized between the Alfred Wegener Institute for Polar and Marine Research (AWI) and the Institut Français de Recherche pour l'Exploitation de la mer (IFREMER), the latter providing the unmanned deep-sea submersible "Victor 6000". AWI and IFREMER offered this unique combination of infrastructure in 2003 to European scientists to permit access on advanced technology in marine research to a broader community. Therefore, this cruise was not only a milestone in the Franco-German cooperation but also an important contribution to the European marine research initiatives. All still pictures and videos taken with "Victor 6000" during the expedition "VICTOR IN THE NORTH" are joint property of AWI and IFREMER with copyright by IFREMER. This material can be used for scientific purposes with the indication of IFREMER's copyright. It would be very much appreciated if the joint effort of AWI and IFREMER in organising the cruise ARK XIX/3 would be mentioned in the acknowledgements of any future publication written on the basis of material collected during the expedition. Any commercial or other than scientific use of either pictures or videos collected with "Victor 6000" needs the written formal approval of IFREMER. The entire cruise report is also available in digital format on a CD-ROM attached to this booklet because many of the pictures and graphs are in colour. All hand written dive log files are permanently stored at the AWI. For a certain period of time the cruise diary will be still accessible via the internet at www.polarstern-victor.de.