Search results for "ahven"

Divergent parasite infections in sympatric cichlid species in Lake Victoria

2018

Parasitism has been proposed as a factor in host speciation, as an agent affecting coexistence of host species in species-rich communities and as a driver of post-speciation diversification. Young adaptive radiations of closely related host species of varying ecological and genomic differentiation provide interesting opportunities to explore interactions between patterns of parasitism, divergence and coexistence of sympatric host species. Here, we explored patterns in ectoparasitism in a community of 16 fully sympatric cichlid species at Makobe Island in Lake Victoria, a model system of vertebrate adaptive radiation. We asked whether host niche, host abundance or host genetic differentiatio…

Eco‐evolutionary dynamics driven by fishing : from single species models to dynamic evolution within complex food webs

2020

Evidence of contemporary evolution across ecological time scales stimulated research on the eco‐evolutionary dynamics of natural populations. Aquatic systems provide a good setting to study eco‐evolutionary dynamics owing to a wealth of long‐term monitoring data and the detected trends in fish life‐history traits across intensively harvested marine and freshwater systems. In the present study, we focus on modelling approaches to simulate eco‐evolutionary dynamics of fishes and their ecosystems. Firstly, we review the development of modelling from single‐species to multispecies approaches. Secondly, we advance the current state‐of‐the‐art methodology by implementing evolution of life‐history…

Lake eutrophication and brownification downgrade availability and transfer of essential fatty acids for human consumption

2016

Article

Seasonal and ontogenetic variability in stomach size of Eurasian perch (Perca fluviatilis L.)

2019

Eurasian perch (Perca fluviatilis) were sampled in April, from May to June and at the end of August to test whether the current season (i.e. feeding conditions) affects the fishes’ stomach size (i.e. volume and weight). A wide range of size data were analysed to reveal the relationship between fish size (length and weight) and stomach size. No significant differences in length-specific stomach volume or stomach weight were found in fish sampled at different times of the year. However, there were differences between seasons in the size of the stomach in relation to body weight, as length-specific body weight changes during the year because of the development of gametes and changes in nutriti…

Macrophytes shape trophic niche variation among generalist fishes.

2017

Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation…

An alloherpesvirus infection of European perch Perca fluviatilis in Finland

2018

The order Herpesvirales includes viruses that infect aquatic and terrestrial vertebrates and several aquatic invertebrates (i.e. mollusks), and share the commonality of possessing a double-stranded DNA core surrounded by an icosahedral capsid. Herpesviruses of the family Alloherpesviridae that infect fish and amphibians, including channel catfish virus and koi herpes - virus, negatively impact aquaculture. Here, we describe a novel herpesvirus infection of wild European perch from lakes in Finland. Infected fish exhibited white nodules on the skin and fins, typically in the spring when prevalence reached nearly 40% in one of the sampled lakes. Transmission electron microscopic examination o…

PISA 2012 : resultatnivån i de åländska skolorna

2014

Poor nutritional quality of primary producers and zooplankton driven by eutrophication is mitigated at upper trophic levels

2022

Eutrophication and rising water temperature in freshwaters may increase the total production of a lake while simultaneously reducing the nutritional quality of food web components. We evaluated how cyanobacteria blooms, driven by agricultural eutrophication (in eutrophic Lake Köyliöjärvi) or global warming (in mesotrophic Lake Pyhäjärvi), influence the biomass and structure of phytoplankton, zooplankton, and fish communities. In terms of the nutritional value of food web components, we evaluated changes in the ω-3 and ω-6 polyunsaturated fatty acids (PUFA) of phytoplankton and consumers at different trophic levels. Meanwhile, the lakes did not differ in their biomasses of phytoplankton, zoo…

Täpläravun (Pacifastacus leniusculus) vaikutus ahventen (Perca fluviatilis) loisyhteisöihin Päijänteellä

2010

Täplärapu (Pacifastacus leniusculus) on tulokaslaji Suomen vesistöissä. Sen on käyttäytymisellään ja ravinnonkäytöllään todettu vähentävän elinalueidensa eliöyhteisöjen monimuotoisuutta. Esimerkiksi Päijänteellä on havaittu joidenkin pohjaeläinten kuten kotiloiden tiheyksien olevan alhaisempia ravun elinalueilla kuin ravuttomilla alueilla. Pohjaselkärangattomat ovat välttämättömiä väli-isäntiä monelle kalan loiselle. Tässä tutkimuksessa selvitettiin, millaisia muutoksia täplärapu voi välillisesti aiheuttaa kalojen loisyhteisöissä muuttamalla pohjaeläinten runsautta. Päijänteeltä valittiin viisi toisistaan riippumatonta ravullista ja ravutonta aluetta. Jokaiselta alueelta pyydettiin mahdolli…

Allochthony, fatty acid and mercury trends in muscle of Eurasian perch (Perca fluviatilis) along boreal environmental gradients

2022

Environmental change, including joint effects of increasing dissolved organic carbon (DOC) and total phosphorus (TP) in boreal northern lakes could potentially affects food web energy sources and the biochemical composition of organisms. These environmental stressors are enhanced by anthropogenic land-use and can decrease the quality of polyunsaturated fatty acids (PUFAs) in seston and zooplankton, and therefore, possibly cascading up to fish. In contrast, the content of mercury in fish increases with lake browning potentially amplified by intensive forestry practises. However, there is little evidence on how these environmental stressors simultaneously impact beneficial omega-3 fatty acid …