The Swedish hydropower needs to be adapted to new legislation requiring modern environmental conditions according to the EU Water Framework Directive. A national strategy suggests how to balance the need for improved ecological status to the need of hydropower and was submitted to the Government in October 2019. To make the adaption towards sustainable hydropower in Sweden, the Älvkarleby power plant needs environmental measures as fish passages to improve connectivity as well as an environmental flow in Kungsådran. The Water Authorities suggests environmental measures in Älvkarleby consisting of a nature-like fishway for the fish to move upstream, a net for guiding the fish downstream and an increased flow in Kungsådran to 20 and 30 m3/s for winter and summer, respectively. In addition, suggestions of measures have been formed by Vattenfall based on the results of a pilot study in the Dal river creating eight scenarios. The scenarios consist of combinations of two different techniques for fish passages (nature-like fishway and a technical fishway), two techniques for guiding the fish downstream (angled bar racks and a net) and two suggestions of flows in Kungsådran; keep the flow in today’s level of an average of 3 and 12 m3/s (for winter and summer, respectively) or 7.5 m3/s all year. In this study, the suggested measures are valued in a cost-benefit analysis (CBA), that includes all expected consequences for the suggestions given in the chosen time periods, to evaluate their socio-economic profitability. A CBA tool based on a research project called FRAM-KLIV is used to receive the net present value of the suggested measures. The results show that the measure suggested by the Water Authorities is not found to be socio-economic profitable, when compared to today. This analysis has not been able to monetarize two of the identified consequences. In the CBA eight scenarios are compared to the suggested measure by the Water Authorities, Scenario 1 is valued to be the most socio-economic profitable. Moreover, there are only two Scenarios (number 4 and 8) that is evaluated to not be socio-economic profitable. In this part there is one identified consequence that has not been monetarized. There are uncertainties in the methods of estimating the consequences, which are used as input in the CBA tool, thus affecting the result. In conclusion, to have a trustworthy result there is a need of more thorough investigation for the evaluation to be used in decision making of which measure is valuated to be socio-economic profitable.

Förvaltning av lax är en komplicerad uppgift som kräver stor förståelse för både laxen och de antropogena effekter som påverkar den. Vattenkraftverk har stor påverkan på laxen genom oregelbundna flöden, reducerad vattenföring och barriärer i vandringsvägar. Laxen är beroende av att vandra för att optimera tillväxt, överlevnad och reproduktion. Östersjöns laxbestånd minskade kraftigt mellan 1950- och 1980-talet till följd av dammutbyggnad och överfiske. Redan i början av 1900-talet började det lokala laxbeståndet i älven Ljusnan att sjunka av samma orsaker. Idag finns ingen lax kvar i Ljusnan. För att möjliggöra en återintroduktion av lax krävs möjlighet för vandring och tillgång på reproduktionshabitat. Bollnäsströmmarna bedöms med sina 6,6 km historiskt ha stått för 25 % av hela Ljusnans laxproduktion. Syftet med denna studie var att simulera en återintroduktion av lax i Bollnäsströmmarna och att genom sårbarhetsanalys undersöka om utplantering av romkorn kan resultera i en överlevande laxpopulation. Simuleringarna utfördes med dagens förutsättningar med undantag av att de passagefria kraftverken ersattes med passagelösningar av bästa möjliga teknik. Utöver detta undersöktes effekter av ökad passagedödlighet förbi kraftverken, habitatåterställande åtgärder och utökade supplementära utsättningar av romkorn. Sammanlagt nio sårbarhetsanalyser utfördes i simuleringsprogrammet Vortex. Resultatet av studien visar att utplantering av romkorn kan producera en laxpopulation som överlever under en hundraårsperiod. Efter en initial populationsökning under tio år sjunker dock tillväxten konstant resterande nittio år vilket med största sannolikhet hade resulterat i en utdöd population över en större tidsrymd. Den potentiella laxpopulationen var mycket känslig för ökad passagedödlighet med en hög utdöenderisk efter endast en liten ökning. Både habitatåterställande åtgärder och supplementära utsättningar av rom gav positiva effekter på populationsstorleken men inget scenario lyckades producera ett stabilt och livskraftigt bestånd vilket tyder på att fler åtgärder krävs för ett lyckat återintroduktionsprojekt. / Conservation of salmon is a complicated task that requires understanding both the biology of salmon and the anthropogenic impacts affecting it. Atlantic salmon is dependent on its migration to optimize growth, survival and reproduction. Hydropower plants affect salmon by causing highly irregular flows, reduced discharge and barriers along migration routes. The salmon stocks of the Baltic Sea declined considerably between the 1950s and 1980s as a result of dam development and overfishing. For the same reasons the local salmon stock in the River Ljusnan, Sweden began to decline already in the early 1900s, and today there are no salmon left in the River Ljusnan. To restore the population, actions to mediate migration and access to reproduction habitats and rearing habitats are needed. The 6.6 km long river section, “Bollnäsströmmarna”, is estimated to have accounted for 25 % of the total salmon production in the River Ljusnan. The aim of this study was to simulate a reintroduction of Atlantic salmon in Bollnäsströmmarna, and using a population viability analysis (PVA), investigate if stocking of eggs can result in a viable salmon population. Simulations were made on the basis of today’s conditions, with the condition that best practice passage solutions are implemented. In addition, the effects of increased passage mortality, habitat restoration and increased supplementary stocking of eggs were simulated. A total of nine PVA simulation (n= 100) scenarios were performed in the Vortex simulation program. The results of the study show that stocking of eggs can produce a salmon population that has a minimum extinction risk over a one-hundred year period. However, after an initial population increase over ten years, population growth steadily declines for the remaining ninety years, which most likely would result in extinction if a period longer than 100 years was considered. The salmon population was very sensitive to an increase in passage mortality, with a high extinction risk after only a small increase in mortality. Both habitat restoration and increased supplementary stocking impacted the population size positively, but no scenario produced a stable and viable population, which indicates that more measures are required for a successful long-term reintroduction.

Vattenkraftverk och dammar utgör vandringshinder både vid upp- och nedströmsvandring för flertalet fiskarter. En åtgärd för att minska vandringshindrens negativa påverkan på migrerande arter är att anlägga fiskpassager som underlättar upp- och nedströmspassage. Galleravledare med flyktöppning är en åtgärd som syftar till att hindra nedströmsvandrande smolt från att simma in i vattenkraftverksturbiner och riskera förhöjd dödlighet. Syftet med studien var att undersöka funktionen av en galleravledare med tillhörande flyktväg till en naturfåra vid Strömsbro kraftverk i Testeboån. Med hjälp akustisk telemetri undersöktes laxsmoltens vägval vid galleravledaren, dess överlevnad vid passage via naturfåran respektive genom kraftverkets turbiner samt skillnaden i tidsåtgång mellan dessa passagealternativ. Totalt märktes 60 smolt med sändare i mitten av maj 2022. Tio mottagare placerades ut på drygt 5 km av Testeboåns nedersta del. Hög dödlighet (45%) från utsläppsplatsen till kraftverket resulterade i att endast 30 individer inkluderades i studien. Resultatet visade, likt tidigare undersökningar vid Strömsbro kraftverk, att majoriteten (2/3) av smolten simmar genom kraftverket.Ingen dödlighet observerades för smolt som passerade via naturfåran medan dödligheten var 25% för smolten som passerade genom kraftverket. Av de smolt som nådde fram till Strömsbro kraftverk tog sig 64% till Testeboåns mynning, vilket motsvarade totalt 35% av den märkta smolten. Tidsåtgången var betydligt högre i naturfåran jämfört med kraftverket, vilket visar på fördröjning för smolt som passerar Strömsbro kraftverk via naturfåran. Resultaten antyder en dålig funktion av galleravledaren vid Strömsbro kraftverk med förhöjd dödlighet som följd. En orsak kan vara utformningen av galleravledaren. Vidare undersökning av möjligheterna för en förbättrad funktion av galleravledaren vid Strömsbro kraftverk bör vidtas. / Hydropower plants and weirs serve as barriers for both up- and downstream migration for multiple species. To minimize the negative impacts of barriers on migrating fish species, fish passages are constructed to allow for upstream and downstream passage. Angled bar racks together with a bypass are a solution that are meant to lead fish away from the power plants intake. The aim of this study was to investigate the efficiency of an angled bar rack with bypass leading to the old riverbed at Strömsbro hydropower plant in Testeboån River, Sweden. Acoustic telemetry was used to investigate Atlantic salmon smolts passage efficiency at the angle bar rack and subsequent path choice. It was also used to evaluate mortality for both the old riverbed and the passage through the power plant, as well as the difference in time between the two passages. 60 smolts were marked with acoustic transmitters in May 2022 and ten acoustic receivers were placed over the lower 5 km in Testeboån River to evaluate their migration. High mortality (45%) from the release site to the power plant resulted in only 30 individuals being used for the evaluation. The result showed, like former studies at Strömsbro, that the majority (2/3) of the smolt passed through the angled rack and through the power plants intake. There was no mortality for the old riverbed and 25% for the passage through the power plant. Overall, the success of downstream migration past Strömsbro power plant was 35% of marked smolts and 64% of the individuals reaching Strömsbro power plant. Smolt passage took longer through the old riverbed in comparison to the passage through the power plant, which shows some delay for smolts passing Strömsbro power plant through the old riverbed. The result implies low efficiency of the angled bar rack at Strömsbro power plant, leading to increased mortality. The design of the angled rack might be one reason for this. Further investigation about the possibilities to increase the efficiency of the angled rack at Strömsbro power plant should be considered.