An efficient extreme ship response prediction approach in a given short-term sea state is devised in the paper. The present approach employs an active learning reliability method, named as the active learning Kriging + Markov Chain Monte Carlo (AK-MCMC), to predict the exceedance probability of extreme ship response. Apart from that, the Karhunen-Loève (KL) expansion of stochastic ocean wave is adopted to reduce the number of stochastic variables and to expedite the AK-MCMC computations. Weakly and strongly nonlinear vertical bending moments (VBMs) in a container ship, where the former only accounts for the nonlinearities in the hydrostatic and Froude-Krylov forces, while the latter also accounts for the nonlinearities in the radiation and diffraction forces together with slamming and hydroelastic effects, are studied to demonstrate the efficiency and accuracy of the present approach. The nonlinear strip theory is used for time domain VBM computations. Validation and comparison against the crude Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM) are made. The present approach demonstrates superior efficiency and accuracy compared to FORM. Moreover, methods for estimating the Mean-out-crossing rate of VBM based on reliability indices derived from the present approach are proposed and are validated against long-time numerical simulations.
Accurate estimation of the roll damping of a ship is important for reliable prediction of roll motions. In particular, characterization and prediction of parametric roll incidence and other events associated with large roll angles require detailed knowledge about the damping terms. In the present paper, an approach to identify the stability parameters, i.e. linear and nonlinear roll damping coefficients in conjunction with the natural roll frequency, based on onboard response measurements is proposed. The method starts by estimating the encountered wave profile using wave-induced response measurements other than roll, e.g., heave, pitch, and sway motions. The estimated wave profile is then fed into a physic-based nonlinear roll estimator, and then the stability parameters that best reproduce the measured roll motion are identified by optimization. In turn, in-situ identification can be achieved while simultaneously collecting the response measurements. A numerical investigation using synthetic response measurements is made first, then follows an experimental investigation using a scaled model ship. Good results have been obtained in both long-crested and short-crested irregular waves.
The Faroe Islands are currently struggling to find their feet in a new context of globalization and changing international requirements on fishery management best practices, as exemplified by United Nations protocols and agreements. We introduce the Faroese fisheries effort management system for cod, haddock and saithe, which represents an innovative attempt to tackle the challenges of mixed fisheries by means of a combination of total allowable effort implemented through days-at-sea and extensive use of closed or limited access areas. Subsequently, we present and discuss controversies concerning the system's ability (or lack thereof) to achieve a level of fishing effort that produces long-term sustainability. Over the years the system has proven able to evolve and overcome challenges, and the Faroe Islands are currently considering adding a proper fisheries management plan to the system to achieve fishing at maximum sustainable yield. However, finding support for this plan presents a challenge due particularly to an enduring gap between the perspectives of scientists and actors in the catching sector. Finally, we outline some actions that could be taken to reduce the gap and hence facilitate reform of the system: 1) integration of the consultative/advisory process; 2) obtaining tailor-made advice for the Faroese effort management system from the relevant scientific body; 3) establishment of a transparent mechanism for monitoring and regulating fishing effort; 4) clarifying the effectiveness of the prevalent system of closed areas.
The Common Fisheries Policy (CFP) is rooted in the Treaty of Rome. After its completion in 1983, the policy framework was gradually reformed through decennial reviews in 1993, 2003, and 2014. Due to geopolitical, physiographic, and historical reasons, the EU implementation of the CFP is most developed in the North Atlantic Ocean, the North Sea, and the Baltic Sea, and less developed in the Mediterranean and Black Sea. However, the CFP applies throughout European Union (EU) waters, which that are treated as a “common pond.” The CFP has been heavily contested since its introduction, and over long periods was characterized as a management system in crisis. Historically, the CFP has arguably struggled to perform and the policy’s ability to meet its objectives has not uncommonly been undermined by factors such as internally contradictory decisions and inefficient implementation. Since the turn of the century, the policy has changed its course by incrementally institutionalizing principles for a more environmentally orientated and scientifically based fisheries management approach. In general, in the latest decade, fisheries have become increasingly sustainable in both environmental and economic terms. An increasing number of fish stocks under the CFP are being exploited at sustainable levels—a development that is likely to continue, as fish stocks are coming to be more commonly managed along the lines of science-based multi-annual management plans. Consequently, many fishing fleets, particularly those deployed in northern waters, have shown good economic performance in recent years. This development has been further facilitated by the introduction of market-based management principles; in most member states these have been implemented by granting de facto ownership to fishing rights for free in the name of ecological and economic sustainability. This has, however, in many cases also led to huge wealth generation for a small privileged group of large-scale fishers at the expense of small-scale fisheries and smaller fishing communities, as well as society at large; this situation has led to calls for both a fairer distribution of fishing rights—to protect the small-scale sector—and for a resource rent or exploitation fee to be collected for the benefit of society at large, which is the true owner of fishing resources. Consequently, social sustainability, understood as the improved well-being of fishing communities and a fairer sharing out of the benefits derived from fisheries resources, should be a subject for the CFP to consider in the future.
ABSTRACT: Denmark is among the more loyal European Union (EU) member states when it comes to national implementation of the Common Fisheries Policy (CFP). However, even in Denmark several mechanisms contribute to sub-optimal implementation of the CFP. Looking at implementation problems for a relatively loyal member state, this chapter sheds critical light on national implementation of the CFP in the EU as a whole. The chapter initially provides a description of the institutional set-up for fisheries policy-making and implementation in Denmark, including a short historical account of the development of the Danish fisheries and their management since 1983. Subsequently, the chapter provides an understanding of the mechanisms and processes behind the Danish implementation of fisheries policy, arguing that these mechanisms and processes have led to a situation where the goals agreed at the EU level are supplemented or even replaced by national priorities. The chapter concludes that in order to capture the domestic politics associated with CFP implementation in Denmark, it is important to understand the policy process as a synergistic interaction between dominant interests, policy alliances/networks and prevailing discourses. The inability of the EU to ensure that the conservation goals agreed at the EU level are loyally pursued during national implementation is one of the reasons why the EU has been struggling to keep fishing mortality rates at a sustainable level.
This article deals with the implementation of ecosystem-based marine management in the Baltic Sea. It explores and documents in particular the preliminary lessons from environmental and fisheries management with reference to the Helsinki Commission Group for implementation of the ecosystem approach and the Baltic Sea Fisheries Forum, both examples of regionalization processes in order to implement ecosystem-based marine management. The Helsinki Commission Group for implementation of the ecosystem approach is a joint management body for the implementation of the Baltic Sea Action Plan and the European Union's Marine Strategy Framework Directive. The Baltic Sea Fisheries Forum is a new governing body to facilitate regional cooperation in fisheries management. The aim of the article is twofold: a) to describe and discuss two different pathways of regionalization in the Baltic Sea and b) to explore how these forms of regionalization could contribute to the implementation of governance structures needed to implement ecosystem-based marine management at the level of a regional sea – efficiently, legitimately and effectively. We conclude that a nested governance structure could be developed by building upon existing institutions while learning from new initiatives to organize stakeholder involvement.
Optimisation of energy efficiency and operational performance as well as assessment of safety levels and emissions of marine operations require detailed information about the acting wave system. It is possible-with an analogy to classical wave buoys-to estimate the directional wave spectrum by processing sensor measurements of wave-induced responses (e.g., motions and structural responses) from a ship. Compared to other sources of wave data (e.g., buoys, satellites, third-generation wave models), estimation concepts using the ship itself as a buoy provide the wave spectrum at the exact spatio-temporal point, potentially increasing accuracy and with minimal associated cost. This paper gives an overview of the technology, discusses associated uncertainties, and highlights new developments made for estimating waves via measured ship responses.
This paper presents an assessment of the energy harvesting potential from wave-induced motions when producing electricity by linear generators installed on ships. The study estimates an upper maximum energy extraction potential by not considering the electro-mechanical coupling; neither is mechanical and electrical dissipation considered. The analysis of the harvested energy is made using simulated data in a case study investigating three different ships (by size). Specifically, the case study reveals that, in moderate to mildly severe sea states, the power harvested from the environment using linear generators may reach values around 1–2 kW/tons of seismic mass. Thus, it is unrealistic to imagine ship designs where linear generators are thought to provide a ship's necessary propulsion power but, on the other hand, they may serve to supplement the main engine for auxiliary power generation.