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  • 1
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    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 68 (5). pp. 813-822.
    Publication Date: 2019-09-23
    Description: In 1999, marine protected areas (MPAs) were implemented along the west coast of the Big Island of Hawaii, closing ~35% of the coastline to aquarium fishing. Catch per unit effort and total catch of the most commonly targeted fish, yellow tang (Zebrasoma flavescens), have increased since the implementation of the MPAs, yet its abundance has declined by 45% in areas open to aquarium fishing between 1999 and 2007. How effort allocation, harvesting efficiencies, and job satisfaction influence catch productivity and selectivity in West Hawaii’s aquarium fishery are investigated, and how these dynamics explain the discrepancy between catch rates and relative abundance for yellow tang is discussed. Cross-sectional fisher questionnaires, semi-structured fisher interviews, and in situ and ex situ catch analyses were performed. The results indicate that fishers dive deeper when reef fish recruitment is perceived as weak, increase harvest efficiency with larger fishing teams, and intensively harvest “coral-friendly” reef fish to supply the global aquarium fish trade. Experienced fishers were less likely to exit the fishery, and job satisfaction was high despite declining fish stocks. These findings may help explain harvesting efficiencies and fleet investment, underscore the importance for evaluating fisher behaviours, and have potential management implications for other aquarium fisheries.
    Type: Article , PeerReviewed
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  • 2
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    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 68 (6). pp. 1244-1256.
    Publication Date: 2019-09-23
    Description: Temperature effects on Baltic sprat are many and include both direct and indirect effects. Increasing temperature is thought to increase the survival of all early life stages, resulting in increased recruitment success. We quantified the spatially resolved temperature trend for major spawning grounds and depth layers being most relevant for sprat eggs and larvae, using a three-dimensional hydrodynamic model for 1979–2005. Results confirmed an underlying positive temperature trend. Next, we tested these time-series as new explanatory variables in an existing temperature-dependent recruitment function and applied these recruitment predictions in an agestructured ecological–economic optimization model, maximizing for profit. Economic optimal solutions depended upon variability in temperature trajectories. Under climate-change scenarios, mean optimal fishing mortality and related yields and profits increased. The extent of the increase was limited by the general shape of the stock–recruitment model and the assumption of density-dependence. This highlights the need to formulate better environmentally sensitive stock recruitment models. Under the current knowledge of Baltic sprat recruitment, the tested climate-change scenarios would result in a change in management targets. However, to serve as a quantitative management advice tool, models will have to address the above-mentioned concerns
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
    Publication Date: 2018-02-27
    Description: Cod and sprat are the dominant fish species in the Baltic pelagic ecosystem, both of great economic importance and ecologically strongly interlinked. Management of both species is challenged by highly variable recruitment success. Recent studies have identified predation and hydrographic conditions during the egg phase to be of critical importance. Two years of extensive field investigations in the Bornholm Basin, central Baltic Sea, were undertaken. In 2002, a typical stagnation situation characterized by low salinity and poor oxygen conditions was investigated, and in early 2003, a major inflow of North Sea water completely changed the hydrographic conditions by increasing salinity and oxygen content, thereby altering ecological conditions. The goal was to quantify egg mortality caused by predation and hydrography, and to compare these estimates with independent estimates based on cohort analysis. Results indicated high intra-annual variability in egg mortality. Cod and sprat egg mortality responded differently to the major Baltic inflow: mortality related to hydrographic conditions increased for sprat and decreased for cod. On the other hand, predation mortality during peak spawning decreased for sprat and increased for cod.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 4
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 639, 40 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Description: Itinerary and summary On 20 April 2011 Polarstern started its Atlantic transfer from Cape Town to Bremerhaven as last leg of Antarctic cruise ANT-XXVII/4. The cruise was utilized for continuous investigations of atmospheric and marine properties as well as for energy and material fluxes between ocean and atmosphere. The cruise ended in Bremerhaven on 20 May 2011 after a short stop in Las Palmas. The following projects were carried out: 3.1 Autonomous measurement platforms for energy and material exchange between ocean and atmosphere (OCEANET - Atmosphere & Ocean) In order to provide a solid basis for the observational monitoring of energy and material exchange between ocean and atmosphere it is planned to develop an autonomous observation system for operational use onboard cargo- and research vessels. The project is based on a network of expertise between IFM-GEOMAR (CO2-/O2-fluxes, photosynthetic status, energy budget, remote sensing), IfT (lidar measurements), the GKSS research center (ferry box, remote sensing of marine biology with ENVISAT/ MERIS) and AWI-Bremerhaven (CO2-system, marine infrastructure of Polarstern). 3.2 Chemical and physical characterization of marine aerosols on board Polarstern Exchange of gases and aerosol particles between ocean and atmosphere is not well understood currently, although it has received considerably and intensively attention. New measurements were carried out here using a LIDAR system to understand the formation mechanism of secondary fraction in marine aerosols particles and to characterize the optical properties of marine aerosols. 3.3 Aerosols measurements using MICROTOPS In addition to the LIDAR aerosol measurements, optical thickness densities of aerosols were measured by using the MICOROTOPS. 3.4 Rate measurement of cosmic particles in dependence on latitude and weather conditions Continuous rate measurements of cosmic particles allow estimating their dependency on latitude due to the earth’s magnetic field. Simultaneous cloud observations allow investigating whether the concentration of cosmic particles influences cloudiness or vice versa.
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 5
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 638, 122 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Description: ...Diese Dissertation untersucht Klima induzierte Veränderungen der Meeresoberflächeneigenschaften, Eis-Rafting Ereignisse und den äolischen Eintrag organischen Materials in den Nordatlantik während der letzten 4 Ma. Zu diesem Zweck werden Veränderungen in der organischen, geochemischen und mineralogischen Zusammensetzung mariner Sedimente der Integrated Ocean Drilling Project (IODP) Expedition 306 Site U1313 untersucht. Site U1313, eine Nachbohrung der Deep Sea Drilling Project (DSDP) Site 607, liegt im Nordatlantik (41ʿ N; 32,57ʿ W) an einer der klimatisch sensibelsten Positionen der Welt. Das Hauptziel dieser Doktorarbeit besteht in der Rekonstruktion der langfristigen Entwicklung von Klimavariabilitäten im Nordatlantik, um zu einem besseren Verständnis der noch weitgehend unbekannten Mechanismen, die den quartären Klimawandel bestimmten, beizutragen...
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 6
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 627, 243 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 7
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 634, 242 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 8
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 626, 200 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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