Technical and economic consequences of increasing fish growth through the use of waste heat in aquaculture

The effects of water temperature on fish feeding, metabolism and growth are examined with special reference to the common carp (Cyprinus carpio L). The effects of variations in temperature and ration level on the technical and economic characteristics of a simplified fish farming system are then established, and optimum levels for these parameters determined for a range of conditions using a computer model. The main advantage of increasing the farm temperature is a reduction in feed costs as a result of improved food conversion efficiency. Such a saving is however only valid for within species comparisons. Increased temperature also leads to a considerable reduction in holding costs, although the effect on total unit cost is not dramatic because of the relative insignificance of holding costs in the overall operating costs. Increased temperature has relatively little effect on water requirements/ costs per unit of production. The many extra costs and problems likely to be associated with the use of heated effluents are discussed. It is concluded that though heated effluents may be of use in culturing hardy fish or shellfish species with a high market value, it holds little promise as a means of producing large quantities of cheap fish for the mass market

A new glacier inventory for 2009 reveals spatial and temporal variability in glacier response to atmospheric warming in the Northern Antarctic Peninsula, 1988–2009

The Northern Antarctic Peninsula has recently exhibited ice-shelf disintegration, glacier recession and acceleration. However, the dynamic response of land-terminating, ice-shelf tributary and tidewater glaciers has not yet been quantified or assessed for variability, and there are sparse published data for glacier classification, morphology, area, length or altitude. This paper firstly uses ASTER images from 2009 and a SPIRIT DEM from 2006 to classify the area, length, altitude, slope, aspect, geomorphology, type and hypsometry of 194 glaciers on Trinity Peninsula, Vega Island and James Ross Island. Secondly, this paper uses LANDSAT-4 and ASTER images from 1988 and 2001 and data from the Antarctic Digital Database (ADD) from 1997 to document glacier change 1988–2009. From 1988–2001, 90 % of glaciers receded, and from 2001–2009, 79 % receded. Glaciers on the western side of Trinity Peninsula retreated relatively little. On the eastern side of Trinity Peninsula, the rate of recession of ice-shelf tributary glaciers has slowed from 12.9 km² a⁻¹ (1988–2001) to 2.4 km² a⁻¹ (2001–2009). Tidewater glaciers on the drier, cooler Eastern Trinity Peninsula experienced fastest recession from 1988–2001, with limited frontal retreat after 2001. Land-terminating glaciers on James Ross Island also retreated fastest in the period 1988–2001. Large tidewater glaciers on James Ross Island are now declining in areal extent at rates of up to 0.04 km² a⁻¹. This east-west difference is largely a result of orographic temperature and precipitation gradients across the Antarctic Peninsula. Strong variability in tidewater glacier recession rates may result from the influence of glacier length, altitude, slope and hypsometry on glacier mass balance. High snowfall means that the glaciers on the Western Peninsula are not currently rapidly receding. Recession rates on the eastern side of Trinity Peninsula are slowing as the floating ice tongues retreat into the fjords and the glaciers reach a new dynamic equilibrium. The rapid glacier recession of tidewater glaciers on James Ross Island is likely to continue because of their low elevations and flat profiles. In contrast, the higher and steeper tidewater glaciers on the Eastern Antarctic Peninsula will attain more stable frontal positions after low-lying ablation areas are removed

Modelling outburst floods from moraine-dammed glacial lakes

In response to climatic change, the size and number of moraine-dammed supraglacial and proglacial lake systems have increased dramatically in recent decades. Given an appropriate trigger, the natural moraine dams that impound these proglacial lakes are breached, producing catastrophic Glacial Lake Outburst Floods (GLOFs). These floods are highly complex phenomena, with flood characteristics controlled, in the first instance, by the style of breach formation. Downstream, GLOFs typically exhibit transient, often non-Newtonian fluid dynamics as a result of high rates of sediment entrainment from the dam structure and channel boundaries. Combined, these characteristics introduce numerous modelling challenges. In this review, the historical, contemporary and emerging approaches available to model the individual stages, or components, of a GLOF event are introduced and discussed. A number of methods exist to model the stages of a GLOF event. Dam-breach models can be categorised as being empirical, analytical or numerical in nature, with each method having significant advantages and shortcomings. Empirical relationships that produce estimates of peak discharge and time to peak are straightforward to implement, but the applicability of these models is often limited by the nature of the case study data from which they are derived. Furthermore, empirical models neglect the inclusion of basic hydraulic principles that describe the mechanics of breach formation. Analytical or parametric models simulate breach development using simplified versions of the physically based equations that describe breach enlargement, whilst complex, physically-based codes represent the state-of-the-art in numerical dam-breach modelling. To date, few of the latter have been applied to investigate the moraine-dam failure problem. Despite significant advances in the physical complexity and availability of higher-order hydrodynamic solvers, the majority of published accounts that have attempted to reconstruct or predict GLOF characteristics have been limited, often by necessity, to the use of relatively simplistic models. This is in part attributable to the unavailability of terrain models of many high-mountain catchments at the fine spatial resolutions required for the effective application of numerically-sophisticated codes, and their proprietary (and often cost-prohibitive) nature. However, advanced models are experiencing increasing use in the glacial hazards literature. In particular, the suitability of emerging mesh-free, particle-based methods for simulating dam-breach and GLOF routing may represent a solution to many of the challenges associated with modelling this complex phenomenon. Sources of uncertainty in the GLOF modelling chain have been identified by various workers. However, to date their significance for the robustness of reconstructive and predictive modelling efforts have been largely unexplored and quantified in detail. These sources include the geometric and material characterisation of moraine dam complexes, including lake bathymetry and the presence and extent of buried ice, initial conditions (freeboard, precise spillway dimensions), spatial discretisation of the down-valley domain, hydrodynamic model dimensionality and the dynamic coupling of successive components in the GLOF model cascade

Evaluation of FAO’s support to the implementation of the Code of Conduct for Responsible Fisheries

The Code of Conduct for Responsible Fisheries (CCRF), generated out of the preparations for and conduct of the 1992 United Nations Conference for Environment and Development, was adopted by FAO Members on 31 October 1995. In the Resolution adopting the Code, FAO member countries (MCs) also requested that FAO Secretariat provided support to those among them, that most required assistance for making progress in the implementation of the Code

Numerical modeling of glacial lake outburst floods using physically based dam-breach models

The instability of moraine-dammed proglacial lakes creates the potential for catastrophic glacial lake outburst floods (GLOFs) in high-mountain regions. In this research, we use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed within a generalised likelihood uncertainty estimation (GLUE) framework, to quantify predictive uncertainty in model outputs associated with a reconstruction of the Dig Tsho failure in Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Multiple breach scenarios were produced by differing parameter ensembles associated with a range of breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was found to exert a dominant influence over model performance. The downstream routing of scenario-specific breach hydrographs revealed significant differences in the timing and extent of inundation. A GLUE-based methodology for constructing probabilistic maps of inundation extent, flow depth, and hazard is presented and provides a useful tool for communicating uncertainty in GLOF hazard assessment

Evidence gathering in support of sustainable Scottish inshore fisheries: work package (5) final report: improving market intelligence and fishery production co-ordination in Scottish inshore fisheries – a pilot study

[Extract from Executive Summary] This work package builds on a broad brush scaling of the volume, composition and geographical disposition of inshore sector landings to inform examination of market linkages, identify supply chain weaknesses, and explore opportunities to increase producer prices – focusing on a small number of case study areas. Analysis has sought to identify opportunities and mechanisms by which the inshore sector might counter the disadvantages it routinely suffers due to its small-scale of operation and its geographic peripherality.Publisher PD

Evidence gathering in support of sustainable Scottish inshore fisheries: work package (6) final report: integrating stock management considerations with market opportunities in the Scottish inshore fisheries sector – a pilot study

In June 2014, Hambrey Consulting successfully responded to a call for tenders for research to undertake a pilot assessment of the potential economic and associated benefits of establishing minimum market landing size (MMLS) in excess of minimum legal landing size (MLS) for shellfish; and to evaluate if such an intervention could be undertaken at a regional level. The project was originally conceived as including 3 case studies, but the scope of the research led us to focus mainly on the trawl and creel fishery for Nephrops prosecuted by the fleet based in Skye and SW Ross. The basic framework for the assessment approach was to: Develop an economic profile of the case study area and its fishing fleet; Review and synthesise existing data on size profile of the catch, the factors that affect size, including costs associated with individual (vessel) actions or strategies to increase the size profile of the catch; Analyse market and market trends, and the prices for different sizes of product; Develop economic models of representative fishing enterprises, taking account of the relationships between costs and returns and the size profile of the catch; Use plausible scenarios to explore likely short term economic consequences of any changes in MMLS; Use yield and utility per recruit analysis to explore possible yield benefits associated with increased MMLS.Publisher PD