Rõngu jõe potentsiaalsete forellikoelmute hapnikurežiimist
Laen...
Kuupäev
2019
Kättesaadavus
7.09.2019
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Forelli ja tema kudemisharjumusi on uuritud, aga väga vähe on uuritud koelmu substraati
vertikaalselt. Töö eesmärk oli uurida potentsiaalsete forellikoelmute substraadi
vertikaalset hapnikurežiimi, setteosakeste suurust ja orgaanilise aine hulka.
Hapnikusisalduse mõõtmised toimusid kolmes eri tüüpi kohas (mudane, liivane,
kruusane) spetsiaalselt konstrueeritud hapnikusondiga. Pärast hapnikusisalduse mõõtmist
võeti mõõtmiskohtadest setteproovid. Setteproovid viidi laborisse, kus nendest arvutati
pärast põletamist, kaalukao alusel, orgaanilise aine hulk. Setted fraktsioneeriti
märgsõelumise teel fraktsioonidesse >10 mm, 10-7 mm, 7-5 mm, 5-2 mm, 2-1 mm, 1-0,5
mm ja <0,5 mm. Selgus, et analüüsitud kohtadest vastas ainult kruusane substraat täielikult
koelmu nõuetele, mida ka kirjanduse andmed kinnitavad. Liivase substraadi puhul oli küll
hapniku olukord hea, aga liialt domineerisid peenemad fraktsiooniosakesed. Koelmuks ei
sobinud üldse mudane substraat, mida ka eeldati. Tulevikus tuleks parema ülevaate
saamiseks teha täpsemaid analüüse: määrata ära kõik fraktsioonid, mis on suuremad kui
10 mm, tuvastada iga fraktsiooni orgaanilise aine osakaal ning teha laboratoorseid katseid
kontrollitud tingimustes vooluveeakvaariumis. Kuna forelli edukus sõltub suuresti
sobivate koelmute olemasolust, siis saab töös kasutatud sondi abil hinnata looduslike ja
kunstkoelmute hapnikurežiimi.
Though brown trout and its spawning habits have been studied much, the vertical properties of its spawning substrate have been investigated less. The aim of the work was to research the vertical oxygen regime of the potential trout spawning substrates, the size of the sediment particles and the amount of organic matter in sediments. Oxygen measurements were made at three sites of different structure (muddy, sandy, gravel) with a specially designed oxygen probe. After measuring the oxygen content, sediment samples were taken from the measuring sites and brought to a laboratory where their organic matter content was estimated by burning method. Sediments were fractionated by wet sieving into fractions of > 10 mm, 10-7 mm, 7-5 mm, 5-2 mm, 2-1 mm, 1-0.5 mm and <0.5 mm. As a result, it became clear that only the gravel substrate corresponded to the requirements of the trout spawning site, as previously described in the literature. In the case of sand substrate, the oxygen situation was good but the finer fraction particles dominated. The muddy substrate, as it was expected, was not suitable for trout spawning. In the future, it would be good to carry out a more accurate analysis of all fractions greater than 10 mm, and to identify the percentage of organic matter in each fraction, as well to perform laboratory tests under controlled conditions in a fluviarium. Since the success of the trout depends heavily on the existence of suitable spawning places, investigations of natural and artificial spawning places of trout by means of the oxygen probe used in the current theses would be beneficial.
Though brown trout and its spawning habits have been studied much, the vertical properties of its spawning substrate have been investigated less. The aim of the work was to research the vertical oxygen regime of the potential trout spawning substrates, the size of the sediment particles and the amount of organic matter in sediments. Oxygen measurements were made at three sites of different structure (muddy, sandy, gravel) with a specially designed oxygen probe. After measuring the oxygen content, sediment samples were taken from the measuring sites and brought to a laboratory where their organic matter content was estimated by burning method. Sediments were fractionated by wet sieving into fractions of > 10 mm, 10-7 mm, 7-5 mm, 5-2 mm, 2-1 mm, 1-0.5 mm and <0.5 mm. As a result, it became clear that only the gravel substrate corresponded to the requirements of the trout spawning site, as previously described in the literature. In the case of sand substrate, the oxygen situation was good but the finer fraction particles dominated. The muddy substrate, as it was expected, was not suitable for trout spawning. In the future, it would be good to carry out a more accurate analysis of all fractions greater than 10 mm, and to identify the percentage of organic matter in each fraction, as well to perform laboratory tests under controlled conditions in a fluviarium. Since the success of the trout depends heavily on the existence of suitable spawning places, investigations of natural and artificial spawning places of trout by means of the oxygen probe used in the current theses would be beneficial.
Kirjeldus
Bakalaureusetöö
Kalanduse ja vesiviljeluse õppekaval
Märksõnad
bakalaureusetööd, jõeforell, kudemine, hapnikurežiim