C. Skov

Technical University of Denmark | DTU · National Institute of Aquatic Resources

Citizen science platforms are an alternative to traditional survey methods for collecting data from recreational fisheries. However, to supplement data collection, challenges associated with these platforms must be addressed, such as lack of recruitment and sustained engagement. Some platforms distinguish between recruitment and data contribution i...

The role of the ICES Working Group on Recreational Fisheries Surveys (WGRFS) is to compile and validate data from European countries' recreational fisheries and contribute to the ICES advisory process regarding marine recreational fisheries (MRF) issues. In 2023, WGRFS actively engaged in various aspects of MRF, involving the consolidation and eval...

Recreational fisheries are dynamic social-ecological systems. Identification of anticipated future trends supports the design of policies and management to deliver outcomes for fisheries resources, users, and communities. To this end, we applied a forecasting method (i.e., Delphi survey) to recreational fisheries in five Nordic countries. The surve...

Genetic data have greatly increased means to understand fish marine migration behaviours at large spatial scale within a quantitative framework. The anadromous sea trout is a prized target of recreational fishery and an important ecosystem component in freshwater and marine coastal habitats in large parts of temperate northern Europe. Nonetheless,...

The Delphi method was used to gather assessments from 93 experts about drivers of future angling participation by locals and tourist anglers in Denmark, Finland, Iceland, Norway, and Sweden. The main drivers of future angling participation related to habitat and fish populations, and access to and information about fishing. For Norway and Finland,...

Preventing the spread of aquatic invasive species is an important management action. Identifying the characteristics of lakes that are susceptible to invasion creates an opportunity for management groups to prioritize limited resources for high-risk areas. In this study, we leveraged big data from a popular fishing app and other publicly available...

Catch-and-release (C&R) is a common practice in recreational angling for northern pike (Esox lucius), whereby the angler releases the fish back into the water after capture with the expectation that it will survive with negligible stress and physical injuries. This may not always be the case, as hooking in critical anatomical locations , such as gi...

Animal movement is a multifaceted process that occurs for multiple reasons with powerful consequences for food web and ecosystem dynamics. New paradigms and technical innovations have recently pervaded the field, providing increasingly powerful means to deliver fine-scale movement data, attracting renewed interest. Specifically in the aquatic envir...

Large reductions in fish biomass are common both as a method of managing lake ecosystems by fish removals (biomanipulation) and as naturally occurring fish kills. To further understand how fish reductions change feeding patterns of fish, we studied the diets of small‐ to medium‐sized roach (Rutilus rutilus) and European perch (Perca fluviatilis) on...

Sustainable management of lakes requires us to overcome ecological, economic, and social challenges. These challenges can be addressed by focusing on achieving ecological improvement within a multifaceted, co‐beneficial context. In‐lake restoration measures may promote more rapid ecosystem responses than is feasible with catchment measures alone, e...

Despite the widespread use of stock enhancements to improve fisheries across the world, there is a lack of robust knowledge under which conditions fish stocking provides additive effects rather than merely replacing a fraction of natural recruitment. Fully controlled and replicated studies at the level of entire ecosystems are needed to provide ans...

It is well recognized that COVID-19 lockdowns impacted human interactions with natural ecosystems. One example is recreational fishing, which, in developed countries, involves approximately 10% of people. Fishing licence sales and observations at angling locations suggest that recreational fishing effort increased substantially during lockdowns. Ho...

The global COVID-19 pandemic resulted in many jurisdictions implementing orders restricting the movements of people to inhibit virus transmission, with recreational angling often either not permitted or access to fisheries and/or related infrastructure being prevented. Following the lifting of restrictions, initial angler surveys and licence sales...

The ICES Working Group on Recreational Fisheries Surveys (WGRFS) role is to summarize, and quality assure recreational fishery data and feed into the ICES advisory process on marine recreational fisheries (MRF) issues. In 2022, WGRFS continued to work on many aspects of MRF including collation and review of national survey programmes; assessment of...

The northern pike (Esox lucius) is an iconic predatory fish species of significant recreational value and ecological role in the Baltic Sea. Some earlier studies indicate local declines of pike in the region, but a thorough spatial evaluation of regional population trends of pike in the Baltic Sea is lacking. In this study, we collate data from 59...

Sea trout (anadromous brown trout, Salmo trutta L.) is a popular recreational angling target species in the Baltic Sea region and beyond. Across countries, a substantial part of angled sea trout is released after capture either due to management regulations or due to voluntary decisions by the anglers. However, information about post-release impact...

It is manifest that COVID-19 lockdowns extensively impacted human interactions with natural ecosystems. One example is recreational fishing, an activity which involves nearly 1 in 10 people in developed countries. Fishing licence sales and direct observations at popular angling locations suggest that recreational fishing effort increased substantia...

Sea trout (anadromous brown trout, Salmo trutta L.) is a popular target species for angling in Denmark and many other countries. In most regions, angling for sea trout is regulated by measures such as minimum landing sizes, bag limits or seasonal closures. This can lead to high catch and release (C&R) rates. However, information about angler behavi...

Temporary summer stratification is probably a common, but easily overlooked phenomenon in many shallow lakes, because short-term temperature stratification and mixing events are not easily discovered by routine samplings. We used two years of high frequency measurements and monitoring of 5-m deep and hypereutrophic Lake Ormstrup, Denmark to study t...

Animal migration is one of the most spectacular and visible behavioural phenomena in nature with profound implications for a range of ecological and evolutionary processes. Successful migration hinges on the ability to exploit temporary resources (e.g. food) and evade threats (e.g. predators) as they arise, and thus the timing of migration is often...

The recent return of Atlantic bluefin tuna to northern Europe following the recovery of the east Atlantic stock has sparked substantial public and scientific interest. This is particularly true for recreational anglers in Denmark, who often consider Atlantic bluefin tuna to be the catch of a lifetime. This attitude has previously sustained a substa...

As the popularity of recreational fishing gathers global momentum, so does the importance of knowing the number of active anglers and their spatial behaviour. Conventional counting methods, however, can be inaccurate and time-consuming. Here we present two novel methods to monitor recreational fishing applied in Kaunas water reservoir (ca 65 km2),...

Human activities are the leading cause of biological invasions that cause ecologic and economic damage around the world. Aquatic invasive species (AIS) are often spread by recreational anglers who visit two or more bodies of water within a short time frame. Movement data from anglers are, therefore, critical to predicting, preventing, and monitorin...

Understanding satisfaction is an important aspect of the management of recreational fisheries. We investigated fishing trip satisfaction from data collected via a Danish citizen science platform that allows anglers to report information from their fishing trips through a smartphone application and a webpage. Trip satisfaction was related to a set o...

Fish larvae play an important structuring role for their prey and show ontogenetic shifts in diet. Changes in diet differ between species and habitats and may also be affected by turbidity (eutrophication). We investigated the diet (stomach content) and the food selection (ratio of ingested prey and prey availability) of roach and perch larvae in a...

Understanding how eco-evolutionary processes and environmental factors drive population differentiation and adaptation are key challenges in evolutionary biology of relevance for biodiversity protection. Differentiation requires at least partial reproductive separation, which may result from different modes of isolation such as geographic isolation...

Inland fisheries make substantial contributions to food security and livelihoods locally, regionally, and globally but their conservation and management have been largely overlooked by policy makers. In an effort to remedy this limited recognition, a cross-sectoral community of scientists, practitioners, and policy makers from around the world conv...

Настоящий документ является техническим документом, способствующим достижению региональных результатов в рамках проекта программы технического сотрудничества ФАО (TCP/RER/3701) «Системы и методологии сбора данных о рыболовстве во внутренних водоемах Европы», финансируемого Региональным отделением ФАО для Европы и Центральной Азии. Данная работа осу...

This work is the result of an international research effort to determine the main impacts of the COVID-19 pandemic on marine recreational fishing. Changes were assessed on (1) access to fishing, derived from lockdowns and other mobility restrictions; (2) ecosystems, because of alterations in fishing intensity and human presence; (3) the blue econom...

Understanding how eco-evolutionary processes and environmental factors drive population differentiation and adaptation are key challenges in evolutionary biology of relevance for biodiversity protection. Differentiation requires at least partial reproductive separation, which may result from different modes of isolation such as geographic isolation...

We tested the feeding behaviour of small European perch (Perca fluviatilis) in a laboratory study during the first 24 h after handling and 23 mm passive integrated transponder (PIT) tag implantation. Feeding commenced almost immediately following tagging and overall feeding patterns were unaffected by tagging. However, untagged perch had more feedi...

Recreational fishing is increasingly included in fish stock assessments globally. Nonetheless, the extent and precision of recreational fisheries data are often limited. Common methods to collect those data are on-site and off-site surveys, both of which are prone to specific biases, whose magnitude is widely unknown. The present study compares dat...

From 11 March to end of May 2020 a lockdown was imposed in Denmark due to the Covid-19 outbreak. Concurrently a 20% increase in sales of mandatory national angling licenses was reported in Denmark, suggesting an increase in angling participation. Here, we use data collected from a citizen science platform for recreational anglers to a) explore whet...

There are often limited data available to support the sustainable management of recreational fisheries. Electronic citizen science platforms (e.g., smartphone applications) offer a cost-effective alternative to traditional survey methods — but these data must be validated. We compared sea trout (Salmo trutta) data from a Danish citizen science plat...

Technology that is developed for or adopted by the recreational fisheries sector (e.g., anglers and the recreational fishing industry) has led to rapid and dramatic changes in how recreational anglers interact with fisheries resources. From improvements in finding and catching fish to emulating their natural prey and accessing previously inaccessib...

Inland fisheries make substantial contributions to food security and livelihoods locally, regionally, and globally but their conservation and management have been largely overlooked by policy makers. In an effort to remedy this limited recognition, a cross-sectoral community of scientists, practitioners, and policy makers from around the world conv...

Smartphone applications (apps) that target recreational fishers are growing in abundance. These apps have the potential to provide data useful for management of recreational fisheries. We surveyed expert opinion in 20, mostly European, countries to assess the current and future status of app use in marine recreational fisheries. The survey revealed...

Citizen science platforms, including smartphone applications, that allow anglers to report information about fishing trips and catches may be a low-cost source of data that can feed into the science and management of recreational fisheries. However, information about potential biases in these data, such as the representativeness of user characteris...

Different migratory species have evolved distinct migratory characteristics that improve fitness in their particular ecological niches. However, when such species hybridize, migratory traits from parental species can combine maladaptively and cause hybrids to fall between parental fitness peaks, with potential consequences for hybrid viability and...

This document is a technical paper contributing to the regional results under an FAO Technical Cooperation Programme project (TCP/RER/3701) on “Systems and methodologies of data collection in inland fisheries of Europe”, financed by the FAO Regional Office for Europe and Central Asia (REU). This work is facilitated by the European Inland Fisheries...

Passive integrated transponder (PIT)‐tagging is commonly used in behavioural studies of fish, although long‐term evaluations of effects from tagging under natural conditions are scarce. We PIT‐tagged common bream Abramis brama, European perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus, released them in their lakes of origin and r...

Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with...

Recreational fisheries hold immense ecological, social, and economic value. The management of these fisheries is increasingly important as we move forward in the Anthropocene. Recreational fisheries managers face several challenges as fisheries often involve diverse social and ecological systems comprised of complex feedback and stakeholder motivat...

There is a need to develop comparable data collection and analysis systems for better implementation of management programs and to evaluate environmental, social and economic values of fisheries in inland waters.

Norway has the highest participation rate in marine recreational fisheries (MRF) in Europe, and is popular among marine tourist anglers. Fishing licences are not required for marine recreational anglers, and the complex and long coastline makes on-site surveys a challenge. A novel approach for spatial sampling was developed and tested in on-site su...

Denmark has long fisheries and aquaculture traditions. Today, the marine commercial fishery has three major fleet categories with respect to the type of target species: (1) fisheries for industrial fish species, (2) fisheries for pelagic human consumption fish species, and (3) fisheries for demersal human consumption fish and shellfish species. Rec...

The foraging activity of large-bodied benthivorous fish has been suggested to be of key importance for maintaining shallow lakes in a turbid state. Since especially the spring ecosystem dynamics determines the successive state of shallow lakes, such impact could depend on seasonality in benthivore activity patterns. However, we do not yet know to w...

The recent focus on a common movement ecology paradigm has increased awareness about the importance of distinguishing different movement patterns for understanding their specific impact on animal ecology and evolution. One specific form of movement is nomadism, where animals move between habitats in an arrhythmic fashion. Although not yet described...

Denne rapport sammenfatter en undersøgelse af lystfiskeriet langs kysten på Fyn gennemført i foråret 2017. Undersøgelsen blev finansieret af den Europæiske Hav- og Fiskerifond og Fiskeristyrelsen via projektet ”For-bedring af forvaltningsgrundlaget for bestande i det rekreative fiskeri” samt af Fisketegnsmidlerne (Projekt ”Lystfiskeradfærd og socio...

Removal of cyprinid fish is a widely used biomanipulation tool to transform turbid shallow eutrophic lakes in north temperate regions into a clear water state. We here evaluate the removal of cyprinids from streams as a supplement to lake fishing. Since cyprinids often aggregate in high densities in lake inlet/outlet streams during winter migration...

There are three basic strategies in the fisheries managers' toolbox that can be used to protect or enhance fish populations (Arlinghaus et al. 2016). The first is enacting fisheries regulations, which manage fishing mortality (i.e., demand, chapter 12) and the other two are habitat management/restoration (chapter 10) and stocking, which attempt to...

Marine recreational fishing (MRF) is a high-participation activity with large economic value and social benefits globally, and it impacts on some fish stocks. Although reporting MRF catches is a European Union legislative requirement, estimates are only available for some countries. Here, data on numbers of fishers, participation rates, days fished...

https://www.crcpress.com/Biology-and-Ecology-of-Pike/Skov-Nilsson/p/book/9781482262902 Emphasizes the progress of pike research during the past two decades Highlights human dimension aspects in recreational fisheries Addresses environmental circumstances on pike populations including the pike individuals This book sets out to bridge the order sca...

Most aquatic animals move during their lifetime, from tiny Daphnia which make vertical migrations between different layers of water to large whales (Cetacea) crossing the oceans. Not surprisingly, studies of spatial ecology are numerous for a wide spectrum of aquatic animals, and the pike Esox lucius Linnaeus, 1758 is no exception. These range from...

Studies of predator-mediated selection on behaviour are critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations. Consistent individual differences in prey behaviour, especially in the propensity to take risks (“boldness”), are widespread in the animal kingdom. Theory predicts that individual b...

Standardised angler diaries could produce useful proxy data for assessing fish population density and size distribution, but few rigorous studies about their utility exist. We use 62 years of angling diary data (1949–2010), from a large mesotrophic lake, to investigate population structure (abundance, mean size and record size) of European perch (P...

Species integrity can be challenged, and even eroded, if closely related species can hybridize and produce fertile offspring of comparable fitness to that of parental species. The maintenance of newly diverged or closely related species therefore hinges on the establishment and effectiveness of pre-and/or post-zygotic reproductive barriers. Ecologi...

In passively operated fishing gear, boldness-related behaviors should fundamentally affect the vulnerability of individual fish and thus be under fisheries selection. To test this hypothesis, we used juvenile common-garden reared carp (Cyprinus carpio) within a narrow size-range to investigate the mechanistic basis of behavioral selection caused by...

Abstract Pike in the western Baltic Sea live on the edge of their salinity tolerance. Under physiologically challenging conditions, organism may respond by moving to environmentally more benign areas during critical periods, such as during spawning. We hypothesised that pike in a brackish lagoon (8–10 ppt salinity) would perform spawning- and feedi...

Recreational fisheries surveys are limited in time and place in many countries. This lack of data limits scientific understanding and sustainable management. Smartphone applications (apps) allow anglers to record the details of their fishing trips and catches. In this study, we describe the opportunities and challenges associated with angler apps a...

Ongoing climate change is affecting animal physiology in many parts of the world. Using metabolism, the oxygen- and capacitylimitation of thermal tolerance (OCLTT) hypothesis provides a tool to predict the responses of ectothermic animals to variation in temperature, oxygen availability and pH in the aquatic environment. The hypothesis remains cont...