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- Gyllenhammar, Andreas, et al.
(author)
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A mesocosm fish farming experiment and its implications for reducing nutrient load on a regional scale
- 2008
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In: Aquacultural Engineering. - : Elsevier BV. - 0144-8609 .- 1873-5614. ; 38:2, s. 117-126
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Journal article (peer-reviewed)abstract
- This work presents results from a mesocosm fish farming experiment. The main aim of the work was to put the results from the experiment into a wider context dealing with an approach to get zero - or even - negative nutrient fluxes from fish cage farms on a regional scale. To quantify the nutrient loading of phosphorus and nitrogen from net cage aquaculture, a standard dynamic mass-balance model approach was used. A comparison was made between responses from two feeding scenarios with rainbow trout (Oncorhynchus mykiss). One set was given a commercial pelleted fish food the other food with fresh herring inclusion. We have shown that on a regional scale, a zero nutrient load situation may be achievable if the wild fish from the given region account for about 11% of the fish food. In the mesocosm experiment, we also tested different approaches to calculate the growth of the cultivated fish and one can conclude that there are no major differences in using the different sub-models for the interpretations to get zero emissions but different growth functions do give different dynamic responses for the fish growth. We have also tested if it is important to account for denitrification. Under the given conditions this is not the case. Critical testing of the modelling has been performed with uncertainty and sensitivity analyses and the major uncertainties were identified in the growth pattern of the fish and the mesocosm biomass nutrient uptake rate. We argue that these results imply that, from an eutrophication point of view, fish farming in open net cages can be viewed as an environmental sustainable industry, if the fish feed includes nutrients that originate from the surrounding waters.
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- Gyllenhammar, Andreas, et al.
(author)
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Flodpärlmussla, Resultat från inventeringarna 1996-2005
- 2005
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Reports (other academic/artistic)abstract
- I denna rapport redovisas de insatser som gjorts för att kartlägga Jämtlands läns bestånd av flodpärlmussla (Margaritifera margaritifera). En kartläggning av historiska bestånd har gjorts, mestadels baserad på litteraturstudier. I rapporten redovisas resultaten från det inventeringsarbete som utförts av Länsstyrelsen i Jämtlands län åren 1996-2005. Resultaten presenteras i form av kartor, figurer och tabeller där beståndens geografiska lokalisering, storlek och reproduktionsstatus redovisas. Länet har idag 53 lokaler med bestånd av flodpärlmussla. I 30 stycken av dessa bestånd förekommer reproduktion men i över hälften (18st) är reproduktionen svag. 12 av bestånden har ett uppskattat individantal på över 10000 individer. Jämtland har i dagsläget Sveriges största bestånd av flodpärlmussla. I Storån, norr om Hammerdal, har antalet individer beräknats till 4,5 miljoner. En mer omfattande analys av läget för flodpärlmusslan i länet kommer att göras då inventeringsmaterialet datalagts i större omfattning och då ytterligare miljödata finns sammanställda. Slutsatserna pekar på vikten av att ytterligare miljödata tillgängliggörs för att möjliggöra en fördjupad analys av musselbeståndens och omgivningsparametrarnas status. Slutligen presenteras hur Länsstyrelsens arbete med flodpärlmussla kommer att fortskrida under 2006, med bl a utformning av ett miljöövervakningsprogram och planering av skyddsåtgärder.
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- Gyllenhammar, Andreas, 1972-
(author)
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Predictive Modelling of Aquatic Ecosystems at Different Scales using Mass Balances and GIS
- 2004
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Doctoral thesis (other academic/artistic)abstract
- This thesis presents models applicable for aquatic ecosystems. Geographical Information Systems (GIS) form an important part of the thesis. The dynamic mass balance models focus on nutrient fluxes, biotic/abiotic interactions and operate on different temporal and spatial scales (site, local, regional and international). The relevance and role of scale in mass balance modelling is a focal point of the thesis.A mesocosm experiment was used to construct a model to estimate the nutrient load of phosphorus and nitrogen from net cage fish farming (i.e., the site scale). The model was used to estimate what feeding conditions that are required for a sustainable aquaculture scenario, i.e., a zero nutrient load situation (a linkage between the site scale and the regional scale). A dynamic model was constructed for suspended particulate matter (SPM) and sedimentation in coastal areas (i.e., the local scale) with different morphometric characteristics and distances to the Sea. The results demonstrate that the conditions in the Sea (the regional and international scale) are of fundamental importance, also for the most enclosed coastal areas.A foodweb model for lakes was transformed and recalibrated for Baltic Sea conditions (i.e., the international scale). The model also includes a mass balance model for phosphorus and accounts for key environmental factors that regulate the presuppositions for production and biomasses of key functional groups of organisms. The potential use of the new model for setting fish quotas of cod was examined.For the intermittent (i.e., regional) scale, topographically complex areas can be difficult to define and model. Therefore, an attempt was made to construct a waterscape subbasin identification program (WASUBI). The method was tested for the Finnish Archipelago Sea and the Okavango Delta in Botswana. A comparison to results from a semi-random delineation method showed that more enclosed basins was created with the WASUBI method.
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- Gyllenhammar, Andreas, et al.
(author)
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WASUBI : A GIS tool for subbasin identification in topographically complex waterscapes
- 2005
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In: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 20:6, s. 729-736
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Journal article (peer-reviewed)abstract
- Spatially distributed modelling is dependent on segmentation of the underlying geographic data and the model output could be improved if relevant compartments are found and used. Herein, we present a method for identifying subbasins in complex topographic waterscapes. The method first finds local troughs and then expands them over a friction surface derived from bathymetry. Friction surfaces generated by different cost growth functions were tested, and shown to give consistent results. The model is sensitive to the quality of the underlying topographic dataset and its spatial resolution. WASUBI (WAterscape SUBbasin Identification) is written in ArcView's built-in scripting language, Avenue, and distributed as a program extension. The method is easy to use, only requiring a digital elevation model (DEM) and the user to give the number of basins to be generated. The segmentation method was tested against datasets covering the Finnish Archipelago Sea and the Okavango Delta in Botswana. Test results showed that the WASUBI delineated subbasins were more enclosed than subbasins created by a semi-random delineation method. The objectives of this study was to construct and critically test algorithms for subbasin identification, based only on readily available DEM data, for use in geographic information system modelling.
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