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dc.contributor.advisorJärvalt, Ain
dc.contributor.authorSilm, Maidu
dc.date.accessioned2013-06-04T08:49:40Z
dc.date.available2013-06-04T08:49:40Z
dc.date.issued2013
dc.identifier.urihttp://hdl.handle.net/10492/1136
dc.description.abstractKlaasangerja varud on langenud kriitilisele piirile, mistõttu võttis Euroopa Komisjon vastu määruse, mis kohustab Euroopa liidu liikmesriike tagama 40% hõbeangerjate väljapääsu merre ja andma aru angerjamajandamise tegevuskavast. Antud töös määrati rohkem kui 900 angerja vanus, kokku kaheteistkümnest siseveekogust, aastatest 1999-2012. Otoliidilt vajalike aastaringide esile toomiseks kasutati „põletamise ja murdmise“ meetodit, kus otoliit fikseeriti plastiliini. Saadud pinda vaadati stereomikroskoobist kuni 40-kordse suurendusega. Hüpoteesiks seati olukord, kus angerja kasvukiirused oleks sarnased kõigis võrreldavates veekogudes. Leiti, et väiksemates järvedes olid angerjad enamasti pikemad, väiksema Fultoni tüsedusindeksiga, suurema peaga ja haigestusid kergemini, kui Võrtsjärves. Järeldati, et väiksemates järvedes nagu Saadjärv, Kuremaa, Kaiavere ja Vagula järv, ladestuvad angerjal kiirekasvu perioodil aastaringidest eristatamatud stressiringid, mistõttu saadud tulemus pole adekvaatne. Ülemiste järve teada vanusega 17 ja 18 aastaste angerjate näitel hinnati vanust üle paari aasta võrra. Uuritud järvedest olid selged aastaringid ainsana Võrtsjärve angerjatel. Saadud tulemuste põhjal kasvasid suures madalas järves angerjad keskmiselt 6,7 sentimeetrit aastas, mis oli parem varasemast „in toto“ meetodiga saadud tulemusest. Kusjuures leiti, et klaasangerjana asustatud põlvkonnad kasvasid keskmiselt 0,6 cm aastas kiiremini. Töös püstitatud hüpoteesi paikapidamist ei õnnestunud usaldusväärselt kontrollida, kuna enamuse väikejärvede puhul ei saanud arvukate lisaringide tõttu täpset vanust määrata. Kerkinud probleemi lahendamiseks tuleks kasutusele võtta angerjate märgistamine „PIT tag“ tüüpi märgistega või siis keemiliselt märgistada, mis annaks võimaluse tagasipüügil juurdekasvu otseselt mõõta.EST
dc.description.abstractThe eel stock in the Narva River basin is based on released generations. Before the year of 2001 the eel was released into lake Võrtsjärv mostly as a glass eel, since 2001 to 2010 only as farmed eel. Since the year of 2002, an introduction of farmed eel into smaller lakes, like the lake Kaiavere, Vagula, Saadjärv and after the year of 2003 into lake Kuremaa began. The hypothesis of my thesis states that the growth rate of eel is similar in all inland waters of Estonia. To prove that I viewed more than 900 eel’s otoliths gathered in years 1999 to 2012 (twelve lakes) and treated by „burning and cracking“ method. An eutrophic lake Võrtsjärv, due to its low water level, large mirror surface area and openness to the winds in ice-free periood is well mixed and well oxygenated. I found that the average annual growth rate of the eel released in glass eel stage was faster by 0,6 cm a year compared with the eel released after farming, although the latter were 8 cm longer at the time of release into the lake. General growth rate was very good – 6,7 cm per year, beeing higher than indicated by previous results obtained in 1998 (5,9 cm). In smaller waterbodies with mostly eutrophic and in three of them stratified waters, the eel was longer, had lower condition faktor, larger head, and had suffered under frequent outbreaks of diseases. The growth rate of eel averaged in those lakses as less than 3 cm per year. In lake Kuremaa, where the eel had been suffered by the red fin disease with a number of deaths in recent years, the growth rate had been the slowest. I found that most likely the age of eel is overestimated due to the deposition of supernumerary zones in a rapid growth period. Also, the signifficanly enlarged numbers of official catch prove that the eel of smaller lakes has been over-aged as the eel realeased during the last decade was represented in the yield. In my selection of lakes a lake similar to the eutrophic and evenly mixed lake Võrtsjärv – lake Ülemiste with the data on the date of realease of eel was represented. Depending on the year of capture the eel was aged as 17 or 18 years of age. Despite of that the age of the eel tended to get overestimated by a couple of years. The stated hypothesis was not reliably proved, mostly due to a number of additional false annulus on most of the viewed otoliths.
dc.subjectangerjasEST
dc.subjectVõrtsjärvEST
dc.subjectvanusEST
dc.subjectotoliitEST
dc.subjectkasvEST
dc.subjectmagistritöödest
dc.titleEuroopa angerja (Anguilla anguilla) vanus ja kasv Eesti järvedesen_US
dc.title.alternativeAge and growth of European eel (Anguilla anguilla) in Estonian lakesen_US
dc.typeThesisen_US
dc.date.defensed2013-06-12


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