Examensarbete/Självständigt arbete i biologi, miljövetenskap och hållbar utveckling vid SLU Aqua

Global warming and the efficienty of energy transfer in aquatic ecosystems

Master project in Biology (30-60 credits)

This project aims to resolve how warming of water bodies changes the efficiency of energy transfer from primary producers to fish (i.e. food web efficiency, FWE), and how this may be modified by concurrent change in other environmental drivers. The thesis project will be part of a larger project aiming to identify strategies to maintain ecosystem services in face of multiple environmental stressors, with the goal to maintain the ability of aquatic ecosystems to act as carbon sinks and uphold high production of fish biomass in the future.

Backgrounds

Along with warming, many freshwater and coastal ecosystems are becoming greener and browner (caused by excess humic substances and nutrients). The key factors (temperature, light, nutrients) that control basal energy production in aquatic ecosystems are thus changing. Even though the link between nutrients, light, temperature and algal growth is more or less established, the flow of energy produced by these primary producers to higher trophic levels such as fish is less predictable. The latter is especially true for the combined impact of these environmental drivers on FWE.

Methods

The student (one or several) will set up tank experiment(s) with phytoplankton, zooplankton and fish at our coastal experimental field site in Forsmark to test how warming may change FWE, as well as the potential for browning and/or greening of waters to modify those responses. The detailed set-up and more specific study questions will be decided after discussions between the student and supervisors. You will learn skills such as experimental design, sampling of plankton and fish, identification of aquatic organisms, statistics and scientific writing. Preferred project start would be sometime in the period May-July 2023.

Not only will you gain new knowledge and skills by doing your own project, but you will also become an integrate member of our research group Fish in food-webs, where you will join group meetings and seminars at campus Ultuna in Uppsala. There may also be opportunities for paid part-time work helping out in the field or lab while doing your project and to contribute to a scientific publication.

Contacts

Seals and cormorants - Top predators in Swedish waters

Suggestions of degree projects

The suggested topics are suitable for master student projects. The projects can include field work, lab work, literature studies, data analysis and scientific writing.

The contents and scope of the work can be discussed and adapted to prevailing conditions.

Background

The populations of seals and cormorants in Sweden have increased in size and distribution during the last decades.

Consequently, requirements and needs of information about the ecological roles of seals and cormorants have increased, e.g. for inclusion of top predators in ecological models and for development of ecosystem-based management. In addition, conflicts with fish conservation biology and coastal fisheries have intensified.

At present, relevant information on prey choice and abundance of these predators and their impact on fish stocks is insufficient.

Diet analysis of seals and cormorants

• Diet variability
• Methodology (DNA, image analysis)

Monitoring of seals and cormorants

• Photo-ID
• Camera surveillance
• Regional monitoring, e.g. in marine protected areas
• Abundance estimates

Predator-prey dynamics

• Prey selectivity
• Correlations between diet data and fish monitoring data

Contact:

Hur kan vi gynna den biologiska mångfalden i grunda kustområden?

Masterprojekt i biologi, 30-60 hp

Brinner du för att arbeta med biologisk mångfald i havet? Då är det här projektet något för dig. Projektet bygger på två innovationsprojekt som Helsingborgs stad har arbetat med i Öresund de senaste åren. Visionen i Helsingborgs stad är att arbeta för att öka den biologiska mångfalden i kustområdena.

Bakgrund

Tyvärr har många viktiga livsmiljöer i grunda kustområden försvunnit genom historien, i takt med att Helsingborgs stad utvidgats. De grunda områdena är nyckelområden när man talar om biologisk mångfald. De fungerar både som skafferi och barnkammare för många olika djur och växter.

Speciellt i hamnarna möter djuren raka kajkanter och ingenstans att gömma sig eller hitta mat. Det har Helsingborgs stad försökt göra något åt. I en av de största hamnarna har ett konstgjort rev byggts upp och strukturer har satts upp på kajkanten för att bidra till större komplexitet i livsmiljöerna och därmed fler hem för olika djurarter och alger.

Metod

I detta examensarbete kommer du att vara med och undersöka mer i detalj vad konstgjorda strukturer, som ett rev och strukturer på kajkanter, kan bidra med när vi pratar om biologisk mångfald i kustområden. Närmare bestämt kommer du i projektet att behöva skaffa data om artsammansättning och biomassa vid de olika strukturerna i hamnen och utföra analyser för att se vilka effekter de har. Du kan hjälpa till att forma ditt projekt i den riktning som är relevant för dig. Det finns många alternativ och oavsett vilken väg du väljer kommer du att bidra till ny kunskap om hur kustkommuner och städer kan arbeta aktivt för att öka den biologiska mångfalden i grunda kustområden med fokus på hamnar.

Arbetet utförs som ett samarbete mellan Helsingborgs stad och SLU, under handledning vid SLU av Lena Bergström, Institutionen för akvatiska resurser.  En marinbiolog anställd vid Helsingborgs stad kommer att knytas till projektet och kommer att kunna bistå med expertis i ditt fältarbete och kring biologi i Öresund. Arbetet kan påbörjas från och med höstterminen 2022.

Kontakt

Developing a socio-ecological model for risk assessment in the Baltic Sea

Examensarbete i biologi eller hållbar utveckling vid institutionen för akvatiska resurser, SLU, 15-30 hp

Thesis work in biology or sustainable development at the Department of Aquatic Resources, SLU, 15-30 ECTS credits.

Within this project you will have the opportunity to develop a socio-ecological model for the Bothnian Sea that can be used for future management decisions in collaboration with stakeholders, managers and scientists.

Background: A key aim in ecosystem-based management (EBM) is to establish common goals among stakeholders, as this is expected to enable the continued delivery of ecosystem services, while reducing user conflicts. Socio-ecological models are often used to support this aim. The models help increase the understanding between stakeholders and scientists and investigate how management actions could affect the ecosystem and the people who depend upon it. The Swedish Agency for Marine and Water Management has initiated an EBM pilot project in the southern Bothnian Sea to involve stakeholders in developing an ecosystem-based management that integrates environmental goals with societal goals for the region.

Project: As part of the pilot EBM project, you will develop a socio-ecological model for the Bothnian sea in collaboration with stakeholders, managers and scientists. This, so called fuzzy cognitive model can be used in preparing future management decisions and increase the understanding between managers, stakeholders and scientists of the ecological and societal processes that affect environment status.

Practical work includes conducting interviews with managers and stakeholders and contributing to workshops within the southern Bothnian Sea EBM project. You should be familiar with R, interested in ecosystem-based management and comfortable interacting with people of different backgrounds. No previous modelling experience is necessary.

Contact:

Tourists as biodiversity guardians

Sustainable Development (30 credits, language: English)

Sustainable tourism is committed to making a low impact on the environment and local culture, while helping to generate income and community development. Situated in the Stockholm archipelago, candidate Biosphere, Nämdö archipelago is currently in the process of developing strategies for sustainable tourism. The project involves identifying interactions between conservation and commercialization/tourism and develop strategies for sustainable development (with focus on local fishery and cascade effects, seabirds and top predators and more).

The project will be conducted at Sötvattenslaboratoriet at SLU Aqua, Drottningholm or at the Biosphere office at Nämdö Island.

Contact:

Photos från Nämdöskärgården by Elin Dahlgren, Per Fjärdhäll, Nilla Söderqvist, Anders Söderberg.

Algal toxins in the Baltic Sea – effects on fish health?

Independent work in biology / environmental science, 30 hp.

Within this project you will have the chance to evaluate how exposure to algal toxins in fish from the Baltic Sea has changed over time, and in addition link levels of these substances to fish health data from ongoing environmental monitoring.

Background

The eutrophication of the Baltic Sea is driving large blooms of phytoplankton and cyanobacteria as well as contribute to the occurrence of filamentous algae. The increased abundance of these primary producers can lead to an elevated production

of algal toxins with potentially harmful effects on fish. As part of current environmental monitoring is the programme integrated coastal fish health monitoring – a programme where coastal fish (e.g., perch) is examined in relation to different fish health parameters, from different reference stations along the Swedish coastline. At station Kvädöfjärden in the Baltic Proper, an assumed unaffected area but with large algae blooms during the summer, ongoing health examinations show that perch is far from unaffected. Signs of oxidative stress, immunological response and altered metabolism that cannot be coupled to anthropogenic contaminants points to algal toxins, showing similar effects in ecotoxicological studies, as a potential cause for the deteriorating fish health status in the area.

Project/Method

The project will take advantage of material (perch) collected within the integrated coastal fish health monitoring and stored at the Environmental Specimen Bank at the Swedish Museum of Natural History to do a retrospective study of algal toxins in perch from 1995 to 2019, as well as combine the information with already existing data for fish health. By doing so you will be able to answer how these substances change over time, are the exposure stable or is there an upward/downward trend? You will also have the opportunity to evaluate possible effects of algal toxins in the environment by coupling the chemical data to fish health parameters from the same individuals. Combined, these two research questions will advance the field of algal toxins in the Baltic Sea and contribute to the overall understanding of future needs in this area; no problem exists, annual monitoring is necessary, improved measures to reduce nutrients is warranted, other conclusions?

Practical parts of the project involves sample preparations and aiding in the chemical analysis both done at Stockholm University at the Department of Environmental Science (ACES). In addition to that, data handling and statistical analysis as well as scientific writing will be included and conducted at the Freshwater Institute at Drottningholm, Stockholm.

Contact:

Behavioural effects of tagging in the European eel

Master project/independent project in biology, 30-60 hp

Abstract

In this research project you will explore the behavioural effects of tagging using the European eel. Fish will be collected, held at the laboratory, tagged with PIT-tags, and behavioural experiments will be conducted. The experiments will be videorecorded and analysed using automated software.

Background

Mark and recapture techniques are traditionally used in ecology to estimate a range of parameters, such as migration patterns, growth, survival, and population size. In fish ecology, both external and internal tags are used to answer such questions. According to the 3R principle for ethical use of animals (replace, reduce, refine), tagging methods should affect the animal to the least possible extent. The test animal might be affected by the tagging procedure and/or by the tag itself, and behave in an unnatural way, or even suffer from injury or mortality due to tag and/or handling. Such cases induce suffering to the animal, but cases of less detrimental effects can still bias the data (without harming the fish). Most tagging procedures are quite well developed and does not harm the fish, but non-lethal effects, such as behavioural effects, are important to evaluate since it can bias the data.

This research project will explore the behavioural effects of tagging using the European eel (Anguilla anguilla). It is assessed as critically endangered on the IUCN red list, wherefore data on the effects of different research techniques, such as tagging, are particularly needed.

Method

The student’s task will consist of collecting eels (or use eels that are already available at the laboratory), tag them with PIT-tags and perform behavioural experiments. All experiments will be video recorded. Since the eel is primarily night active, behavioural trials can also be run after sunset, using IR lights and IR sensitive cameras. The specific experiments to perform depends on the student’s interest and whether it’s a 30 or 60 hp thesis. Relevant behaviours to measure include swimming activity, feeding, boldness, sheltering and similar. Swimming activity will be tracked using automated tracking software. Other behaviours will be analysed using behavioural scoring software. Data collected within the project can also be combined with existing long-term data on tagged eels.

The work will take place at the Institute of Freshwater Research, Stockholm - Drottningholm, under supervision of Dr Josefin Sundin. The student should have an interest in fish ecology, fish handling, data analysis, statistics, and scientific writing. The work can commence at any time, depending on whether fish will be collected/bought for the experiment, or if using eel that are already available at the laboratory.

Contact:

Migration behaviour and survival of the European eel

Master project/independent project in biology, 30-60 hp

Abstract

In this research project you will explore migration behaviour and survival of the European eel in a natural river. When the eels start their migration back to the Sargasso Sea, they are hindered by hydropower plants. You will track tagged eels and investigate their migration behaviour and quantify hydropower induced mortality.

Background

River ecosystems serve an important role for biodiversity, but they also provide renewable energy via hydropower electricity production. Hydropower plants, however, hinder natural river connectivity and often involve the construction of dams, causing severe ecological damage to numerous organisms. The critically endangered European eel (Anguilla anguilla) is one of many diadromous species that suffers greatly from hydropower plants. It is affected both by up- and downstream migration barriers, hydropower induced mortality, and habitat destruction and alteration. Our knowledge on the effects of hydropower on the European eel is currently insufficient to provide policymakers and stakeholders with tools to improve the conditions.

Recently, the Government Offices of Sweden decided on a national plan to retrial the environmental legal conditions for all hydropower plants. This enormous project aims to ensure that all hydropower plants in Sweden follow national and international (EU) environmental legislation, which is currently not the case for most hydropower plants. In general, detailed knowledge about the negative effects of hydropower on river connectivity and diadromous species is lacking from natural systems. This means that we are currently lacking the knowledge that will very soon be needed within the national retrial plan. This project will fill some of those knowledge gaps.

Method

The student’s task will consist of tracking tagged eel in a river system. Depending on start date, the student can also be involved in the tagging procedure. In that case, collecting and caring for the fish will be part of the work. The migration data will be used to estimate survival (including hydropower induced mortality) and movement. Data collected within the project can also be combined with existing data on migration and survival.

The work will take place at the Institute of Freshwater Research, Stockholm - Drottningholm, and at river Kävlingeån in Skåne (southern Sweden). The work will be supervised by Dr Josefin Sundin. The student should have an interest in fish ecology, fish handling, data analysis, statistics, and scientific writing. Since some eels have already been tagged within this system, the work can commence at any time by analysing existing data. Additional tagging will be conducted in ~May and September 2022.

Contact:

Salmon health

Independent work in biology / environmental science, 30-60 p

The health situation for our native salmon is worrying, both in the Atlantic and in the Baltic Sea. Disease outbreaks (bleedings, erythemas and fungal infections) along with well-studied reproductive disorder (M74), are reported by most Nordic countries. The reason(s) behind the failing salmon health are unclear and it is not known how the various symptoms are related. To mitigate stock collapses, research and monitoring efforts to shed light on the magnitude and cause of the deteriorating salmon health, are of the essence.

The project aims to increase our understanding of wild salmon health using new techniques (non-invasive sampling using scales, genetics and more). The projects contains fieldwork along with data management and analysis.

Svartmunnad smörbult – förvandla risk till resurs

15-60 hp

Den svartmunnade smörbulten är en fiskart med ursprung från Svarta havet och Kaspiska havet och har sannolikt kommit via barlastvatten till Östersjön. Den rapporterades första gången 1990 i Gdanskbukten där den nu är den vanligast förekommande kustnära fiskarten. År 2008 rapporterades arten för första gången i Sverige, i Karlskrona skärgård, och den finns nu också från Kalmarsund och upp till Gävlebukten, samt runt Gotland och i Göteborg.

Den svartmunnade smörbulten är en invasiv art med hög reproduktionstakt och hög tolerans för olika miljöfaktorer. Det finns risk för att den kan komma att konkurrera med andra bottenlevande arter och även äta rom och yngel från inhemska arter men den kan också vara en resurs för rovfisk och för människor. En uttalad risk är att arten vandrar upp i sötvatten och här behövs kunskap om dess vandringsförmåga och om vilka barriärer som kan hindra arten att ta sig upp i fiskvägar. För att nyttja arten och utveckla effektiva metoder för fiske behövs kunskap om hur arten beter sig vid olika fiskeredskap. Nedanstående projektförslag är experimentella studier som bidrar med kunskap på båda dessa viktiga områden och de är en del av forskningsprojektet Svartmunnad smörbult – förvandla risk till resurs.

Alla experiment utförs i Älvkarleby, vid Dalälven söder om Gävle, antingen vid SLU Fiskeriförsöksstation (FFS) eller vid Vattenfalls experiment anläggning Laxeleratorn. Beroende på bakgrundskunskaper och intresse kan examensarbetet göras antingen inom biologi eller miljövetenskap med utrymme för egna frågeställningar. Omfattning är flexibel och examensarbetena kan göras på kandidat- eller masternivå.

1. Vandringsförmåga (15-60hp), praktiska arbetet utförs under 3-6 veckors tid i Aug/September i Laxeleratorn med eventuell komplettering vid FFS i oktober för 60hp arbetet. I det här experimentet studeras hur svartmunnad smörbult och två andra arter, öring och stensimpa, klarar av att vandra i en konstgjord fiskväg vid olika vattenhastigheter och med olika barriärer. Examensarbetet kan göras på en eller flera arter beroende på omfattning. Arbetet går även att göra under senare del av året på filmat material.
2. Beteende vid fiskeredskap (15-60hp), praktiska arbetet utförs under 2-3 veckors tid i September i Laxeleratorn. I det här experimentet studeras hur svartmunnad smörbult beter sig vid olika utformning av fiskeredskap i syftet att designa effektiva metoder att fånga arten Arbetet går även att göra under senare del av året på filmat material.

Kontakt

Svartmunnad smörbult – förvandla risk till resurs | Externwebben (slu.se)

Foto: Isa Wallin och Anna-Li Jonsson, SLU.

Testing a new tool for non-invasive individual identification of fish using eye-recognition software

Master project/independent project in biology, 30-60 hp

Abstract

In this research project you will explore the possibility to use eye-recognition software as a non-invasive tool for individual identification of fish. Fish will be collected, held at the laboratory, and photographed over time. The photographs will be analysed with iris-recognition software to evaluate the method.

Background

Mark and recapture techniques have traditionally been used in ecology to estimate a range of parameters, such as population size, migration patterns, growth and survival. In fish ecology, both external and internal tags are used to answer such questions. According to the 3R principle for ethical use of animals (replace, reduce, refine), non-invasive methods should be used whenever possible, and the need to develop new techniques is evident.

This research project will explore the possibility to use eye-recognition software as a non-invasive tool for individual identification of fish. The specific species to work with can be decided together with the student, but we suggest working with the Northern pike (Esox lucius). Pike is a highly targeted species for recreational fishing. Currently, it is common practice to catch, photograph and release the fish alive (catch and release fishing). Within a citizen science context, a photograph-based identification technique could greatly advance our understanding of pike ecology and simultaneously benefit fish welfare. Another suggestion for study species is the European eel (Anguilla anguilla). It is assessed as critically endangered on the IUCN red list, wherefore non-invasive research techniques are particularly needed.

Depending on whether the student wishes to do a 30 or 60 hp thesis, the project can be combined with testing whether the body patterns along the side of the pike can be used for identification.

Method

The student’s task will consist of photographing fish at fixed intervals during a determined time period. Collecting and caring for the fish will be part of this work. The photos will then be analysed using the VeriEye software (Neurotechnology). Body patterns can be analysed using ImageJ software, or AI identification (depending on the development stage of the latter software). If photos are available from elsewhere, this project can be adapted to online teaching, where all supervision will take place via zoom meetings. The student will in that case receive digital photos and analyse them from wherever the student is resident.

The work will take place at the Institute of Freshwater Research, Stockholm - Drottningholm, or online, under supervision of Dr Josefin Sundin and Dr Göran Sundblad. The student should have an interest in data analysis, statistics and scientific writing. The work can commence at any time, depending on availability of fish photographs (if the project is done online) or when the study species can be collected and photographed.

Contacts:

Estimating recreational fishing effort in Lake Mälaren

Master project in biology, SLU Aqua, 30-60 hp.

Background

Recreational fishing is a popular activity with several human benefits. Excessive fishing can however have negative effects on fish stocks. In many areas in Sweden, fishing with handheld gears is open access, meaning that anyone can fish. The lack of registration poses challenges for estimating recreational fishing pressure, a key variable for a sustainable fisheries management. To increase our knowledge on recreational fishing in Sweden, the Department of Aquatic Resources conducts yearly surveys of recreational fishing.

This research project will use data collected during the summer of 2020 in Lake Mälaren. The field study focused on the pikeperch (Sander lucioperca) trolling fisheries, and consisted of two parts. The first part was an intercept creel survey, where local fishers were counted and intercepted during fishing for interviews regarding gear, effort and catch. The creel survey covered three larger areas sampled on a subset of days. To complement the creel survey, continuous counting of effort was conducted at selected sites using time-lapse cameras. The two surveys thus covered i) large areas – few occasions and ii) small areas – many occasions. By combining the two survey techniques, the aim is to estimate total recreational fishing effort and provide advice for optimisation of future surveys.

Depending on whether the student wishes to do a 30 or 60 hp thesis, the project can focus on either or both of the two data collection methods.

Method

This project requires an interest in survey design and estimation statistics. Practical work will consist of digitizing the data, including counting effort from the cameras and statistical analysis. The work can be performed online or at the Institute of Freshwater Research, Drottningholm, under the supervision of Dr Göran Sundblad and Dr Nuno Prista (stationed at the Institute of Marine Research, Lysekil).

The student should have an interest in data analysis and statistics. Some knowledge of recreational fishing is advantageous but not necessary. The work can commence at any time.

Contacts:

Giant eels in dusty newspaper archives - historical research in support of a modern protection plan

Examensarbete i miljövetenskap vid institutionen för akvatiska resurser, SLU, 30 hp - Thesis project in environmental science at the Department of Aquatic Resources, 30 ECTS credits

Background

The population of the European eel Anguilla anguilla (L.) is distributed from the North Cape to the Nile Delta, and in all waters in-between – in a panmictic population. That whole stock is derived from a single spawning location, in the far Sargasso Sea (Bermuda) – youngsters drift to our continent and migrate into inland waters; maturing eels leave our rivers and swim back to the Sargasso. Throughout the whole distribution area, small-scaled fisheries occur, targeting different life stages and using a wide variety of techniques. During the 20th century, the population has gradually declined to ~10% of its former abundance; since 1980, recruitment of youngsters from the ocean rapidly declined too. In 2007, the EU adopted the Eel Regulation for the protection and recovery of the stock. In this context, knowledge on the history of the stock and fishery may contribute to the effective protection, and the recovery of this remarkable fish.

Problem description

Circumstantial evidence indicates that the eel stock might have been in decline since the early-1800s, mostly due to habitat loss (draining of swamps) and migration barriers (dams). In the early 1900s, technical innovation and better marketing enabled the development of commercial fisheries, primarily in mainland Europe, mostly for export to Germany (steam trains!), for smoking (Dekker 2019ai). These commercial fisheries (500 to 5000 kg per fisher per year, thousands of fishers) replaced the former subsistence/artisanal fisheries (5 to 500 kg per fisher per year, millions of fishers). Historical sources documenting the subsistence/artisanal fisheries are almost absent, while the documentation of the commercial fisheries is incomplete until ~1950 (Dekker 2019bii). The research question now is: did the replacement of subsistence/artisanal, by commercial fisheries intensify the exploitation pressure, or not? And did this exploitation contribute to the decline of the stock? This requires the comparison of undocumented decades, to little documented decades. In the absence of the regular type of information (catches, efforts, prices, …), it was noted that newspapers regularly publish short articles about the catch of a giant eel. These stories usually indicate date, location, and size of the eel (quantified information!) If exploitation pressure increased, one would expect the size of these giants to diminish, or the number of reports to go down. In Dutch, the conger (sea-eel) and the river-eel share common names, so species identity is a problem. Splitting up results by habitat-type, however, solved that. Note that not many giant river-eels were reported before 1900, and that their size diminished almost consistently over time, since 1900. This intriguing result needs confirmation from other countries; and other countries might improve our insight in the how and why. Any other country (in Western Europe) will be of value, especially since you as a native speaker will be much more able to understand historical stories than I am.

Job description

Newspaper archives are often available on-lineiii, and most archives offer a search engine. The student will explore these archives, master the data retrieval procedures, extract the data and compile a database. Though the Dutch results set a clear example, unknown problems might occur, for which creative solutions must be found. Aiming at a consistent data set, a large amount of time will go into the rigorous extraction procedures. However, in my experience, more time was lost on intriguing stories about eel distracting my attention, than on the extraction itself (e.g. a butcher’s wife, calling her eight eels to assemble for their feeding hour). Creativity and ingenuity will be required, to deal with historical complexities and unforeseen problems. Analysis of the compiled data, and reporting. Joint publication in a popular article (national), and potentially a contribution to the final scientific article (international).

Study load

Since all data are in on-line archives, this project is not time-bound, nor location specific (visits to the physical archives?). Estimated time: three - six months? Time load will depend strongly on the complexity of the archives, the national tradition and culture around eels, and your own focus. This job might fit students in history or socio-ecology as well.

Contact:

Examensarbeten om laxfisk i Dalälven (kandidat/master,
15‐30 hp)

SLU:s Fiskeriförsöksstation i Älvkarleby producerar cirka 140 000 laxar och öringar per år för Dalälven. En förutsättning för ett miljövänligt och djuretiskt vattenbruk är att det bedrivs forskning på avel och odlad fisk. Här pågår forskning och miljöanalys och här finns akvarier, bäckar och älv för experiment, och dessutom kunnig personal. Vi söker nu examensarbetare till:

1. Överlevnad hos lax och öringsmolt

Skarven har pekats ut som en potentiellt viktig predator på smolt (utvandringsmogena lax och öring ungar) men vetenskapliga uppskattningar av skarvens inverkan idag i Dalälven saknas. Eftersom en del av den lax och öring smolt som sätts ut i Dalälven märks med Pit‐tag finns det en möjlighet att leta efter dessa märken i områden där skarvarna haft sina kolnoier. Projektet innebär främst scanning av pit‐tag märken i skarvkolonier längs kusten men även genomgång av spybollar från skarv och andra fåglar kan inkluderas. Fältinsamling utförs under hösten efter häckningen, dvs någon gång under sep‐nov 2020 eller senare.

2. Förbättrad kvalitet hos utsatt fisk

Det är eftersträvansvärt att den fisk som sätts ut så mycket som möjligt liknar den vilda fisken. Ett problem vid många kompensationsodlingar av laxfisk att smolten som sätts ut har skador på sina fenor och även att de växer för snabbt och är för feta jämfört med den vilda fisken. I detta projekt undersöks foderregimens inverkan på kondition, överlevnad och fenskador hos odlad fisk. Även undersökningar av olika tätheter av fisk kan inkluderas. Projektet kan utföras i stort sett när som helst mellan Mars‐December.

3. Historiska trender hos lekande fisk i Dalälven

Vid Fiskeriförsöksstationen har avelsarbete på lax och öring utförts

under nära 100 år. Under denna tid har data på den fisk som vandrar in från havet samlats in vilket möjliggör analyser av förändringar hos lax & öring i Dalälven över tid i t.ex. storlek, kondition, äggstorlek mm. Arbetet kan antingen vara helt teoretiskt och göras när som helst på året, eller involvera provtagning av fisken under antingen avelsfisket (aug) eller romtagningen (okt).

Beroende på bakgrundskunskaper och intresse kan examensarbetet göras antingen inom ekologi eller miljöanalys med utrymme för egna frågeställningar. Omfattning är flexibel och examensarbetena kan göras på kandidat‐ och masternivå.

Kontakt:

Study on cost-effective sampling of Baltic cod stomachs for the purpose of multispecies modelling

Master project (examensarbete) in Ecology (30-60 credits)

The paradigm shift from single species to ecosystem based fisheries management (EBFM) requires a broader, mechanistic and more in-depth understanding of marine ecosystems. Multispecies models able to account for trophic interactions and the effect of environmental variability on populations are an essential tool to move towards an EBFM. To account for predator-prey interactions in age-size structured population dynamic models high quality information on predator consumption, prey preference and trophodynamics are essential. Stomach data provide fundamental information on predators’ diet, but their collection has been generally limited which is considered one of the limiting factors for the implementation of multispecies models for the purposes of fisheries advice within the context of EBFM.

The Baltic Sea has been one of the fortunate exceptions. Here, stomachs of cod, the main predatory fish in the system, have been collected for decades. This dataset is important not only for the implementation of advanced multispecies models for EBFM in the Baltic, but also because it can serve as a benchmark to design future stomach sampling programs for the Baltic and other ecosystems.

This master project aims to explore the spatial and temporal correlation among the cod stomachs and the implications of sampling design and sample size for the estimation of the main processes linked to the implementation of multispecies models. The analyses are expected to yield alternative strategies of stomach sampling in Baltic cod and highlight costeffective sampling schemes which sampling intensity appropriately quantifies cod predation on clupeids in the Baltic and beyond.

Requirements: good skills in spoken and written English, basic statistical skills and familiarity with R programming (ability to write simple own functions).

Work location: Lysekil

Contacts:

Study on the population structure of herring in the central and western Baltic Sea based on the analysis of growth and otolith shape

Master project (examensarbete) in Ecology (30-60 credits)

Stock assessment of herring in the southern Baltic is currently based on a rigid geographical definition of stock boundaries which allocate herring western of Bornholm Island to the so called Western Baltic Spring spawning herring stock and herring on the eastern side of Bornholm to the large central Baltic herring stock. In reality, in this region herring reproduce in coastal habitats along the southern Swedish coasts and along the entire southern Baltic coast from the western to the eastern limits of the basin giving origin to a number of subcomponents within these two stocks.

The relationships among the different sub-components within and between the two stocks are poorly understood, as well as the level of mixing and geographical extents of overlap between the different components belonging to the two stocks remain unknown. This lack of knowledge on population structure has profound implications for the management of herring in the Baltic, both in terms of diversity and productivity.

This master project aims to evaluate the relationships between some of the main herring spawning components in the southern Baltic Sea to contribute to the harmonization of stock assessment units definitions and population structure. Moreover, the analyses are expected to identify solid baselines for future discrimination of the main herring components occurring in mixed catches of commercial fisheries and scientific survey across this broad geographical region.

Requirements: good skills in spoken and written English, basic statistical skills (familiarity with multivariate analyses is an advantage).
Work location: Lysekil.

Håller maten måttet? Energiinnehåll i födan hos sillgrisslor i Östersjön

Sillgrisslor är marina, fiskätande topp-predatorer som finns runt hela norra halvklotet. De kan vara viktiga indikatorer på förändringar i ekosystem som exempelvis utsläpp av miljögifter och förändringar i fiskebestånd. Långtidsstudier har visat att man genom att följa sillgrisslorna på deras häckningsplatser kan lära sig mycket om hur ekosystem fungerar och upptäcka förändringar i näringsväven.

På Stora Karlsö utanför Gotland finns Östersjöns största sillgrisslekoloni, ca 15 000 par. Här pågår sedan 1997 ett övervakningsprogram för sillgrisslor, där bland annat överlevnad, reproduktion och födoval studeras.

Att kunna få tag i energirik föda är en förutsättning för att kunna överleva och föda upp en livkraftig unge. Flera studier har visat att sillgrisslans huvudföda är skarpsill (Sprattus sprattus). Nya data visar dock att strömming (Clupea harengus) kan utgöra en ganska stor del av dieten. Hur energiinnehållet ser ut i strömmingar av olika storlekar och hur det förhåller sig till energiinnehållet i skarpsill är idag okänt. Kunskapen är viktig för att utvärdera sillgrisslans bevarandestatus i Östersjön och hur mycket fisk som behöver sparas i havet för att säkerställa dess överlevnad.

Exjobbet handlar om att analysera energiinnehållet i ett antal skarpsillar och strömmingar som samlats in av Havsfiskelaboratoriet i Lysekil. Dessa kommer sedan att analyseras av studenten med hjälp av en bombkalorimeter, vilket är en maskin som kan mäta energiinnehåll. Detta arbete kommer att ske vid SLU i Ultuna. Data från försöken kommer sedan analyseras statistiskt. Projektet är tänkt för kandidatnivå (15 hp) men möjligheter finns också till ett mer omfattande projekt på mastersnivå, exempelvis innefattande fältarbete på Stora Karlsö där sillgrisslornas matningar av ungarna med fisk kan studeras i detalj.

Länkar:

www.balticseabird.com
www.storakarlso.se

Kontakt: