0000000000185862
AUTHOR
Harri Kokko
showing 5 related works from this author
Genome-wide divergence patterns support fine-scaled genetic structuring associated with migration tendency in brown trout
2018
Brown trout (Salmo trutta) exhibit highly diverse life histories varying from resident, slow-growing, and early maturing to migratory, fast-growing, and late maturing, even within single watersheds. We sampled 11 locations within the transboundary Finnish–Russian River Koutajoki watershed to evaluate genomic differences among mainstem and headwater sites, of which some are isolated by migration barriers. Restriction site associated sequencing (RADSeq) revealed that the most headwater localities supported unique, isolated populations with generally lower heterozygosity compared with the mainstem populations. The sampled migratory adults in the three main stems showed signals of admixture de…
Introduced alien signal crayfish (Pacifastacus leniusculus) in Finland : uncontrollable expansion despite numerous crayfisheries strategies
2018
In Finland, massive signal crayfish introductions started towards the end of 1980s, with an estimated total of 2.2 million signal crayfish been stocked before year 2016. During that period, Finnish fisheries authorities have implemented three national management strategies setting guidelines for the crayfish introductions. The main aims of the strategies have been conservation of native noble crayfish stocks and a controlled spreading of the alien signal crayfish within a designated region. In this study, we report the current distribution of signal crayfish in Finland in comparison to the guidelines set in these three national strategies. The present distribution area of the signal crayfis…
It takes time to see the menu from the body: an experiment on stable isotope composition in freshwater crayfishes
2015
For many applications and ecological studies in which wild individuals are brought to laboratory it would be essential to know accurately how fast novel diet is reflected in composition of different tissues. To study the effects of two different diets on the stable isotope composition of freshwater crayfish muscle and hemolymph, we conducted a three month experiment on noble crayfish (Astacus astacus) and signal crayfish (Pacifastacus leniusculus) by feeding them sweet corn (Zea mays) or Baltic herring (Clupea harengus membras) as novel food. During the experiment, the crayfish were given 0.4 g of selected food daily and the amount consumed was recorded. The samples for the stable isotope a…
Jokirapujen ja täplärapujen esiintymisen selvittäminen eDNA-menetelmällä
2021
Vaarantuneiden jokirapukantojen uhkana on vesistöihimme hyvin sopeutunut vieraslaji, täplärapu, ja sen kantama, erityisesti jokiravuille kohtalokas rapuruton muoto. Rapupopulaatioiden paikantaminen ja seuranta on perinteisesti perustunut paikallistietoon ja koeravustuksiin. Viime vuosien aikana ympäristö-DNA:n (eDNA) käyttöön perustuvat menetelmät ovat kehittyneet varteenotettavaksi vaihtoehdoksi perinteisten menetelmien rinnalle. eDNA-menetelmän avulla voidaan vesinäytteestä tunnistaa kohde-eliöt molekyylibiologisin menetelmin. Tämän tutkimuksen tarkoituksena oli selvittää, soveltuuko eDNA-menetelmä käytettäväksi rapupopulaatioiden havainnoinnissa suomalaisissa vesistöissä ja verrata saatu…
Genetic causes and consequences of Brown trout migratory behaviour
2018
Salmonids are among the most famous and economically important migrating organisms, but unfortunately also often endangered because of multiple human activities. As many other salmonids, brown trout exhibits diverse life history types related to migration strategies. Resident brown trout stay in rivers for their entire life. In contrast, migratory trout undergo a physiological and morphological transformation called smoltification before leaving their natal rivers to enter either sea, lakes or larger river sections. While the phenotypic variation between resident and migratory ecotypes is well documented, little is known about the intraspecific genetic variation associated with these differ…