Tonje Knutsen Sørdalen

Tonje Knutsen Sørdalen
Universitetet i Agder | UIA · Department of Natural Sciences

PhD marine biology

About

31
Publications
8,383
Reads
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249
Citations
Introduction
I am a marine ecologist interested in anthropogenic influence on reproductive behavior and sexual selection, selectivity, population dynamics and contemporary evolution in crustaceans and fish. I am currently involved in CoastVision where we are developing and applying computer vision for species and individuals (re-ID). Currently working as Postdoctoral Researcher at University of Agder, Southern Norway with affiliation with Center for Coastal Research. Personal webpage: www.tonjesordalen.com
Additional affiliations
January 2020 - July 2020
Institute of Marine Research in Norway
Position
  • Researcher
August 2019 - January 2020
Universitetet i Agder
Position
  • Professor (Associate)
October 2017 - October 2018
Institute of Marine Research in Norway
Position
  • Engineer
Education
September 2012 - January 2019
University of Oslo
Field of study
  • Marine ecology and evolution
August 2010 - June 2012
August 2007 - June 2010

Publications

Publications (31)
Article
Full-text available
The positive effects of reduced fishing pressure in marine protected areas (MPAs) are now well documented globally. Yet, evidence of MPA benefits from long-term replicated before-after control-impact (BACI) studies and their usefulness in protecting target species are still rare, especially in northern temperate areas. Scientific rigor in the monit...
Article
Full-text available
The deep learning (DL) revolution is touching all scientific disciplines and corners of our lives as a means of harnessing the power of big data. Marine ecology is no exception. New methods provide analysis of data from sensors, cameras, and acoustic recorders, even in real time, in ways that are reproducible and rapid. Off-the-shelf algorithms fin...
Preprint
Full-text available
The deep learning revolution is touching all scientific disciplines and corners of our lives as a means of harnessing the power of big data. Marine ecology is no exception. These new methods provide analysis of data from sensors, cameras, and acoustic recorders, even in real time, in ways that are reproducible and rapid. Off-the-shelf algorithms ca...
Article
Full-text available
This article reviews a suite of studies conducted in a network of coastal Marine Protected Areas (MPAs) in Skagerrak, Southeast Norway. In 2006, Norway’s first lobster reserves were implemented, with the aim of protecting European lobster (Homarus gammarus) through a ban on fixed gear. A before–after control-impact paired series (BACIPS) monitoring...
Article
Full-text available
The movement patterns of three commercially important wrasse (Labridae) species inside a small marine protected area (~ 0.15 km²) on the west coast of Norway were analysed over a period of 21 months. The mean distance between capture and recapture locations varied between 10-187 meters and was species and season specific. The extent of movement was...
Article
Full-text available
The value of interdisciplinarity for solving complex coastal problems is widely recognized. Many early career researchers (ECRs) therefore actively seek this type of collaboration through choice or necessity, for professional development or project funding. However, establishing and conducting interdisciplinary research collaborations as an ECR has...
Article
Full-text available
A wide range of applications in marine ecology extensively uses underwater cameras. Still, to efficiently process the vast amount of data generated, we need to develop tools that can automatically detect and recognize species captured on film. Classifying fish species from videos and images in natural environments can be challenging because of nois...
Article
Full-text available
Small‐scale fisheries (SSFs) tend to target shallow waters, but the depth distributions of coastal fish can vary depending on species, size, and sex. This creates a scope for a form of fishing selectivity that has received limited attention but can have considerable implications for monitoring and management of these fisheries. We conducted a case...
Article
Full-text available
Marine protected areas (MPAs) are increasingly implemented worldwide to maintain and restore depleted populations. However, despite our knowledge on the myriad of positive responses to protection, there are few empirical studies on the ability to conserve species’ mating patterns and secondary sexual traits. In male European lobsters (Homarus gamma...
Article
Full-text available
Size‐based harvest limits or gear regulations are often used to manage fishing mortality and ensure the spawning biomass of females is sufficiently protected. Yet, management interactions with species’ mating systems that affect fishery sustainability and yield are rarely considered. For species with obligate male care, it is possible that size‐spe...
Preprint
Full-text available
A wide range of applications in marine ecology extensively uses underwater cameras. Still, to efficiently process the vast amount of data generated, we need to develop tools that can automatically detect and recognize species captured on film. Classifying fish species from videos and images in natural environments can be challenging because of nois...
Preprint
Full-text available
Size-based harvest limits or gear regulations are often used to manage fishing mortality and ensure the spawning biomass of females is sufficiently protected. Yet, management interactions with species' mating systems that affect fishery sustainability and yield are rarely considered. For species with obligate male care of eggs, it is possible that...
Technical Report
Full-text available
I Prosjektet «Kunnskapsbasert innovasjon for optimal ressursutnyttelse i leppefiskeriet» har Havforskningsinstituttet (HI) og Fjordservice Flekkefjord samarbeidet om å øke kunnskapen om ressursgrunnlaget for fiskeriet etter leppefisk i Skagerrak. Prosjektet ble finansiert av Regionalt forskingsfond Agder og Fjordservice Flekkefjord. I dette prosje...
Chapter
Our understanding and ability to effectively monitor and manage coastal ecosystems are severely limited by observation methods. Automatic recognition of species in natural environment is a promising tool which would revolutionize video and image analysis for a wide range of applications in marine ecology. However, classifying fish from images captu...
Preprint
Full-text available
Our understanding and ability to effectively monitor and manage coastal ecosystems are severely limited by observation methods. Automatic recognition of species in natural environment is a promising tool which would revolutionize video and image analysis for a wide range of applications in marine ecology. However, classifying fish from images captu...
Thesis
Full-text available
Well-functioning mating systems are perceived as vital for population growth rate and resilience to environmental change, but we know surprisingly little about the interplay between human-induced mortality and the mating systems of exploited marine species. Fishing and hunting can reduce densities, shift sex ratios and often targets individuals wit...
Article
Full-text available
Removing individuals from a wild population can affect the availability of prospective mates and the outcome of competitive interactions, with subsequent effects on mating patterns and sexual selection. Consequently, the rate of harvest-induced evolution is predicted to be strongly dependent on the strength and dynamics of sexual selection yet, the...
Technical Report
Full-text available
Hummerfisket har en lang historie i Norge og har vært en viktig inntektskilde for mange kystsamfunn. Siden 1970-tallet har derimot bestanden vært på et historisk lavt nivå. Til tross for høye priser på hummer kan hummerfisket nærmest karakteriseres som økonomisk utryddet; det er svært begrenset kommersiell lønnsomhet i dette fiskeriet mer. Fritidsf...
Article
Wrasse (Labridae) fisheries have increased markedly in Norway since 2010. Wrasse are being used as cleaner fish in salmonid aquaculture to control sea-lice infestations. However, fundamental knowledge on the demography and abundance of the targeted wrasse populations in Norwegian waters is lacking, and the consequences of harvesting at the current...
Article
Fishery-induced changes in sex ratios can have negative effects on reproductive rates and affect sexual selection and evolutionary trajectories. Here, we investigate sex- and size-selectivity of the fishery for corkwing wrasse (Symphodus melops) in Western Norway. The males that build and guard nests (nesting males) grow faster than females and sne...
Article
Size selective harvesting can also be selective on sex in species displaying sexual size dimorphism (SSD). This has potential consequences for mating systems and population dynamics. Here, we assessed spatial variation in SSD and body size in eight Norwegian populations of corkwing wrasse (Symphodus melops), a species where males either mature as n...
Article
Full-text available
Decapod crustaceans exhibit considerable variation in fertilisation strategies, ranging from pervasive single paternity to the near-ubiquitous presence of multiple paternity, and such knowledge of mating systems and behaviour are required for the informed management of commercially-exploited marine fisheries. We used genetic markers to assess the p...
Presentation
Recent studies have shown that harvesting wild population may exert direct selection on growth rate independently of size, as fast growth and correlated behaviour traits may increase the probability of being captured in fisheries. Harvesting on species with sexual dimorphism in growth can therefore be selective against the faster growing sex. This...
Poster
Full-text available
Corkwing wrasse (Symphodus melops) is a temperate wrasse displaying both sex and male dimorphism and is targeted in a size selective commercial fishery which has increased dramatically since 2008. Wrasses are supplied alive to salmon farms as cleaner fish to combat infestations of Salmon lice. In previous studies, growth and maturation has been fou...
Thesis
Full-text available
Understanding the mechanisms driving mating systems is intricate for wild populations of species where behavioral observations are difficult, but nonetheless imperative for harvested species. This study investigated the occurrence and frequency of multiple paternity for the European lobster (Homarus gammarus) in a marine reserve (MPA) and in a heav...

Questions

Question (1)
Question
We are setting up an experiment in order to study overall productivity and reproductive success of individuals with 1) different "sneaker" male proportions and 2) small vs. large dominant males in indoor fish tanks. However, it will take some time to get enough sneaker males (and smaller males) to start up the experiment and meanwhile the individuals suited for the design are sorted and kept in different tanks.
I am starting to worrying that this "time-out" may perhaps affect their eagerness to mate, building nests, court, spawn when the match-making experiment starts. Some have now been in these acclimatization tanks for about 3 weeks without entering the experiment, and they may have to be there 2-3 more weeks. Should I replace them or use them?

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Projects

Projects (4)
Project
CoastVision will use the power of deep learning to refine and extend a computer vision pipeline for detecting, classifying and sizing the key fish species in shallow water coastal ecosystems, facilitating a transition to fully automated video analysis. Our models will be trained on data sets from several different surveys, ensuring cost-efficient development of routines that will be widely applicable. Computer vision for re-identifying (re-ID) individuals solely based on their unique visible features will also be developed. This novel aspect of CoastVision could ultimately provide new opportunities to obtain detailed knowledge about behaviour and population dynamics in wild fish populations, with minimal negative impact on animals and habitats and at a low cost. Our focal species for re-ID are Atlantic cod, ballan wrasse and corkwing wrasse, commercially important species with complex, high-contrast skin patterns. To generate the necessary training data for re-ID we will use synchronized radio frequency identification and camera systems. CoastVision’s automated video analysis pipeline will be integrated into ongoing ecosystem surveys and case studies whose main objective is to better understand the factors that affects the reproduction, recruitment and survival of commercially important coastal species. As such, CoastVision will contribute to independent, but complementary, research objectives. The project will advance the international research front for applied machine learning in marine ecology, which ultimately can revolutionize our ability to observe, understand and respond to ecological change at scales far more refined than is currently possible.
Project
Wrasses are intensively harvested in Scandinavia and on the British Isles, where they are deployed as cleaner fish in salmon farms. What are the consequences for wrasse populations and the coastal ecosystems? Main objectives: 1. Selective harvesting: Understanding how selective fisheries affect species composition, phenotypic distributions and the consequences for population dynamics and mating patterns. Contrasting slot-size limits vs. minimum size limits. 2: Eco-effects: Investigating the wider ecosystem effects of depleting wrasse populations. 3: Consequences of translocations: What happens when wrasse escapes into genetically distinct populations?
Project
We seek to provide new knowledge on the interactions between mating systems, life history variability, and selective fisheries using empirical data on morphology, growth, survival, and reproduction in wild populations of lobster and wrasse fishes.