Search results for "ALAT"
showing 10 items of 4241 documents
Return of the Apex Predator : How Brown Trout (Salmo trutta) Re-Establishment Shapes an Ecosystem
2021
Re-establishment of a declined apex predator fish species in a lake ecosystem may have dramatic effects on other fish and plankton community already inhabiting the ecosystem. We studied mechanistically potential impacts of re-establishment of the brown trout (Salmo trutta) in the west-central European Lake Constance focusing on two commercially important fish species: whitefish and Eurasian perch. We compared simulation model outputs from two versions of an allometric trophic network model for Lake Constance, one with and one without the trout as the apex predator. The re-establishment of the declined brown trout reduced the perch population directly by predation and indirectly by increased…
Production of feeds for African catfish Clarias gariepinus using plant proteins
2012
Elinkeinokalatalouden mosaiikki
2005
Impacts of anthropogenic factors on fish community structure in Lebialem-Mone Forest Landscape of Cameroon
2010
Two sites of the Cross River within the Lebialem-Mone forest landscape of Cameroon were chosen, one of the sites faced with human activities (test site) and the other with no human pressure (control site). The lengths and weights of fish obtained from both sites were analyzed in SPSS. Fish communities living within these 2 sites were compared after collecting fish from them using gill nets within 2 months of sampling (September-October 2009). Questionnaires were distributed to the fishers to respond to questions related to their fishing practices. Each fish from a sample of 240 fishes obtained from both sites was identified with its length and weight recorded. Fishing pressure constitutes t…
Age is not just a number : Mathematical model suggests senescence affects how fish populations respond to different fishing regimes
2021
Senescence is often described as an age-dependent increase in natural mortality (known as actuarial senescence) and an age-dependent decrease in fecundity (known as reproductive senescence), and its role in nature is still poorly understood. Based on empirical estimates of reproductive and actuarial senescence, we used mathematical simulations to explore how senescence affects the population dynamics of Coregonus albula, a small, schooling salmonid fish. Using an empirically based eco-evolutionary model, we investigated how the presence or absence of senescence affects the eco-evolutionary dynamics of a fish population during pristine, intensive harvest, and recovery phases. Our simulation …
Yläkouluun siirtyneiden oppilaiden kalojen lajintuntemus
2013
Children are studying fishes in the 5th and 7th grades in Finland, so they get basic knowledge about fishes that live in Finland. In upper comprehensive school almost all pupils have tried fishing during their life. The aim of this study was to find out how well 7th grade students are able to identify fish species. In addition, I tried to identify factors that influence possible differences in these skills between the pupils. The material was collected from 12 upper comprehensive schools. The schools were located in three different regions. Each region had four schools, so that there were 2 urban and 2 countryside localities in each region. Altogether, 199 students participated in the surve…
Rysäkalastussaaliiden rakenne ja kalastuksen kestävyys
2019
Nostetta särkikaloista -hankkeen kevään 2019 pilottikohteiden (Pieni Raudanvesi, Haukivesi, Puruvesi, Ruokojärvi) rysäsaalista ja kalaston rakennetta arviointiin särjen, ahvenen ja lahnan osalta ja samalla arvioitiin kalastuksen kestävyyttä olemassa olevien aineistojen ja vasta valmistuneen vajaasti hyödynnettyjen kalalajien saalispotentiaaliarvion (Ruokonen ym. 2019) pohjalta. Saaliin hyödynnettävyyttä elintarvikkeeksi selvitettiin kalalajeittain yhteistyössä kalajalostajien kanssa sekä teoriatasolla käyttäen vertailupohjana Suomen (2017) tekemää selvitystä jalostukseen kelpaavista kalalajeista ja kokoluokista. Lisäksi selvitettiin särkikalojen vaelluksia Pienen Raudanveden ja Haukiveden v…
Suomen ja Ahvenanmaan kalatalouden rakenneohjelmien 2000-2006 väliarvioinnin ajantasaistaminen
2005
Atypical Aeromonas salmonicida -infection as a threat to farming of Arctic charr (Salvelinus alpinus L.) and European grayling (Thymallus thymallus L…
2004
Päivi Pylkön väitöskirjatutkimus osoittaa harjuksen ja nieriän olevan lohikaloista herkimpiä epätyyppisen Aeromonas salmonicida (aAS)–bakteerin aiheuttamalle tulehdukselle. Tautia esiintyy vuosittain useimmilla harjusta ja nieriää viljelevillä laitoksilla. Laitoskasvatus on ensiarvoista vaarantuneiden harjus- ja erittäin uhanalaisten nieriäkantojen säilymiselle. This review summarizes the results of studies on atypical Aeromonas salmonicida (aAS) -infection among farmed Arctic charr (Salvelinus alpinus) and European grayling (Thymallus thymallus) (later referred as charr and grayling, respectively). Specifically, I aimed to characterize the causative agent of aAS -infection, to describe put…