| 31. |
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| 32. |
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| 33. |
- Eklöf, Johan S., 1978-, et al.
(författare)
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Effects of seasonal spawning closures on pike (Esox lucius L.) and perch (Perca fluviatilis L.) catches and coastal food webs in the western Baltic Sea
- 2023
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Marine protected areas have become one of the main tools in the battle to curb marine biodiversity loss and habitat degradation. Yet, implementation of permanent fishery closures has often generated resource user conflicts that ultimately undermine conservation goals. Here we assessed the influence of an alternative and often more accepted measure – seasonal fish spawning closures – on large predatory fish and coastal food webs in the western Baltic Sea (Sweden). In spring 2017, we conducted a multivariable field survey in 11 seasonal closures and 11 paired references areas open to fishing. In each area, pike was sampled through angling, and perch and mesopredators through gillnet surveys. To assess trophic cascades, we measured zooplankton abundance and loss of tethered gammarids from predation. Catches per unit effort of northern pike (Esox lucius) – the main target species in recreational fisheries – were ca. 2.5 times higher per unit effort in closures than reference areas; an effect that may be caused by higher abundance and/or higher catchability of pike in the absence of fishing. Catch and weight per unit effort of the more common predator European perch (Perca fluviatilus), and the mesopredators roach (Rutilus rutilus) and three-spined stickleback (Gasterosteus aculeatus) in survey nets were, however, unaffected by closures. Moreover, a previously hypothesized trophic cascade from perch to zooplankton via three-spined stickleback was supported by the analyses, but appeared independent of closures. Yet, predation risk for tethered gammarid amphipods (a prey of stickleback and an important grazer on macroalgae) was three times higher in fished areas than in closures; a cascading closure effect that may potentially be caused by small predatory fish being less active in protected areas to avoid pike predation. Overall, our results suggest that spawning closures impact pike abundance and/or behavior and could help limit the effects of fishing, but that more research is needed to disentangle i) what mechanism(s) that underlie the protection effect on pike catches, ii) the apparently weaker closure impacts on other fish species, as well as iii) the potential for cascading effects on lower trophic levels. Therefore, new seasonal spawning closures should be implemented in addition to (and not instead of) much-needed permanent closures, which have well-known effects on the wider ecosystem.
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| 34. |
- Erlandsson, Mårten, et al.
(författare)
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Kartering av uppväxtområden för fisk i grunda områden i Östersjön
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I kust- och havsförvaltningen är behovet av heltäckande utbredningskartor över viktiga fiskhabitat stort både på regional och på nationell nivå. Kartorna efterfrågas för både fiskförvaltning, områdesskydd och havsplanering, liksom för hanteringen av tillstånds- och dispensärenden. Habitatmodellering där man kopplar förekomst av arter i provfisken till olika miljövariabler och på så sätt predikterar lämpliga habitat är en metod som gör det möjligt att ta fram heltäckande utbredningskartor utifrån provfiskedata. Hos många fiskarter är speciellt de yngre livsstadierna starkast knutna till specifika miljöer, vilket dels gör dem extra känsliga för påverkan i dessa områden. Samtidigt gör detta dem lämpliga att kartlägga med hjälp av modellering. I denna studie har vi tagit fram heltäckande, högupplösta kartor över uppväxtområden för ett tjugotal av de viktigaste fiskarterna i grunda områden längs svenska kusten i Östersjön. Vi har använt så kallad ensemblemodellering, där ett flertal statistiska metoder kombineras, för att predicera så säkra utbredningskartor som möjligt. Modellerna bygger på data på yngelförekomst under sensommaren, baserat på provfisken utförda med små undervattensdetonationer under sensommaren, i kombination med data på sex miljövariabler (djup, vågexponering, siktdjup, temperatur, salinitet och avstånd till utsjön). Totalt har 5 867 prover från åren 2005– 2018 ingått i modelleringen. Kartorna täcker in kuststräckan från norra Bottenviken till norra delen av skånska kusten, och 0–6 m djup, som utgör huvudsakligt utbredningsområde för merparten av de modellerade arterna. De predicerade utbredningskartorna är användbara till exempel inom fiskförvaltning, havsplanering, arbete med grön infrastruktur och områdesskydd på både nationell och regional nivå.
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| 35. |
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| 36. |
- Fredriksson, Cecilia, et al.
(författare)
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Med gröna ord i påsen. : Om hållbarhetsarbete i butik.
- 2018
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Ingår i: Framtidens fysiska butik : Digitalisering, upplevelser och hållbarhet - Digitalisering, upplevelser och hållbarhet. - 9789186508555 ; , s. 117-124
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 37. |
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| 38. |
- Fredriksson, Håkan, et al.
(författare)
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Gyro feedback of a hydraulic steering system
- 2011
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Ingår i: International Journal of Vehicle Autonomous Systems. - 1471-0226 .- 1741-5306. ; 9:3/4, s. 189-202
-
Tidskriftsartikel (refereegranskat)abstract
- We study the problem to steer, teleoperated as well as autonomously, a tractor that is to operate on a rough and slippery surface. The main idea is to control the effective steering angle of the vehicle. A benefit with this approach is that the vehicle will strive to move in a predefined way irrespective of the surface conditions. To test if the approach is usable we implemented a straight forward p-controller in combination with an estimator of the effective steering angle of the tractor. Our tests indicates that the approach can be useful. Future work would include studies on more advanced control strategies and estimators to reduce some of the problems that we address.
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| 39. |
- Fredriksson, Håkan, et al.
(författare)
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Track loader kinematics
- 2010
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Ingår i: Preprints. - Timisoara : Ed. Politehnica. ; , s. 139-142
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Konferensbidrag (refereegranskat)abstract
- We study the problem to teleoperate a Caterpillar 973c track loader. The track loader and a system for teleoperation are described. A tested and working kinematic model used for dead reckoning is also presented. Track speed sensors combined with a rate gyro are used as input to the model. The model shows good results when tested and compared to a GPS navigation system.
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| 40. |
- Fredriksson Möller, Björn, et al.
(författare)
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CO2-free power generation - A study of three conceptually different plant layouts
- 2003
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Ingår i: American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI. ; 3, s. 255-262
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Konferensbidrag (refereegranskat)abstract
- Ever since the release of the Kyoto protocol the demand for CO2-free processes have been increasing. In this paper three different concepts with no or a very small release of CO2 to the atmosphere are evaluated and compared concerning plant efficiency and investment cost. A novel approach to biomass gasification is proposed to provide fuel for a combined gas turbine cycle, where the biomass is considered to be a renewable fuel with zero impact regarding CO2 in the exhaust gases. The gasification concept used is a Dual Pressurised Fluidised Bed Gasifier (DPFBG) system, using steam and recycled product gas as fluidising agent in the gasification reactor. In the separate combustion reactor air is used as fluidising agent. The second cycle is a hybrid fuelled Humid Air Turbine (HAT) cycle with post-combustion CO 2-separation. Steam used for regenerating the amines in the separation plant is produced using a biomass boiler, and natural gas is used as fuel for the humid air turbine. With this fuel mix the net release of CO 2 can even be less than zero if the exhaust gas from the steam generator is mixed and cleaned together with the main exhaust gas flow. The third cycle proposed is a combined cycle with postcombustion CO 2-separation and the steam generation for the CO 2-separation integrated in the bottoming steam cycle. All power cycles have been modelled in IPSEpro [trademark] (tm), a heat and mass balance software, using advanced component models developed by the authors. An equilibrium model is employed both for the gasification and the separation of CO2 from exhaust gases. All three power cycles show efficiencies around 45%, which is high for a biomass gasification cycle. The HAT and the combined cycle show efficiency drops of about 8 percentage points, due to the post-combustion treatment of exhaust gases.
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