Väljapüükide mõju vähi võõrliikide arvukusele Eestis
Laen...
Kuupäev
2023
Kättesaadavus
02.09.2023
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Invasiivsete võõrliikide levik üle maailma on viimasel sajandil oluliselt kasvanud. Tänu
rahvaarvu suurenemisele, kasvab ka nõudlus toidu järele. Püütakse leida majanduslikult
soodsamaid ja kindlamaid lahendusi, võimalusi ja alternatiive toidusaaduste kasvatamisel
ja tootmisel. Rahavastiku ränded, massilised kaupade veod üle maailma, lemmikloomade
kaubandus (sh akvaariumikaubandus), on võõrliikide leviku põhjuseks. Osaliselt inimeste
teadmatusest kui ka juhuslikult või tahtlikult introdutseerimise teel. Kui võõrliik on uues
kohas leidnud endale sobiva elupaiga, kus ei ole tema tegelik levikuala, võib tema
edasilevik põhjustada ökosüsteemides pöördumatuid kahjustusi. Eestis on alates
2008.aastast registreeritud kolme vähi võõrliigi levikuala, kes ohustavad jõevähi
asurkondi. See on väga tõsine probleem ja sellega tuleb võimalikult kiiresti tegeleda
(EL2023/923). Magistritöö eesmärk on hinnata 2022.a. läbi viidud väljapüükide mõju
signaalvähi arvukusele (Pacifastacus leniusculus) ja pikkuselasele struktuurile veekogus.
Kõikidest teadaolevatest võimalikest tõrjemeetoditest, on Eestis võimalik rakendada
ainult mehhaanilist eemaldamist (mõrraga, nataga jne). Tõrjepüüke teostati mõrdadega
Riksu ojas ja Reo karjääris Saaremaal ja Ropka järves Tartumaal, kus olid ka teada
signaalvähi levikualad. Väljapüükide tulemusel vähenesid signaalvähkide
asustustihedused levikualades oluliselt. Asustustihedust vähkide arvukuse hindamiseks,
kasutatakse populatsiooni tiheduse hindamise skaalat CPUE (catch per unit effort),
mõrraööl saadud isendite arv jagatakse püügil kasutatud mõrdade arvuga. Riksu ojas
CPUE langes 0,73, Reo karjääris 0,05 ja Ropka järves 0,04 ühiku võrra. Eemaldatud
isenditest üle poolte, 52,7% olid emased, mis aitab edaspidi pidurdada signaalvähi
arvukuse kasvu. Kogu püügiperioodil domineerisid püükides suuremad isendid (67%
signaalvähkidest), kes olid suguküpsed või kohe suguküpsust saavutamas (<85mm).
Edasileviku peatamiseks, tuleks vajadusel kasutada ka tõkete rajamise meetodit, mida
saab rakendada Riksu ojas.
Mõrdadega signaalvähkide väljapüükide tulemusel kõigis kolmes veekogus
asustustihedus ja asurkondade arvukus langes oluliselt.
The non-native introduced species distribution has spred from all over the world significantly. Due to population increase, the demand for food is also increasing. People are trying to find more economically favorable and reliable solutions, possibilities and alternatives in the cultivation and production of food products. Population migrations, mass transportation of goods around the world, pet trade (including aquarium trade), all of this is the cause of the spread of non-native introduced species. Partly due to people’s ignorance as well as accidental or intentional introduction of species. When a foreign species has found a suitable habitat in a new place, where is not its actual distribution area, then its further spread may cause irreversible damage to ecosystems. In Estonia, Since 2008, the distribution area of three introduced species of crayfish has been registered, which threaten crayfish populations. This is a very serious problem and needs to be addressed as soon as possible (EL 2023/923). The aim of the master’s thesis is to evaluate the impact of fishing carried out in 2022 on signal crayfish (Pacifastacus leniusculus) abundance and longitudinal structure. Of all known possible control methods in Estonia, it is possible to implement only mechanical removal (baited traps). Control fishing was carried out with traps where there were known signal crayfish distribution areas: in Riksu Stream, Reo quarry in Saaremaa, and in Ropka Lake in Tartumaa. As a result of fishing, the population densities of signal crayfish in the distribution areas decreased significantly. To estimate the number of crayfish, the population density estimation scale CPUE (catch per unit effort) is used. The number of crayfish obtained on the night of the trap is divided by the number of traps used in fishing. CPUE decreased by 0.73 units ja Riksu Stream, 0,05 units in Reo quarry, and 0,04 units in Ropka Lake. From specimens removed, more than half (52,7%) were females, which helps to slow down the increase in the number of signal crayfish in the future. During the entire fishing period, catches were dominated by larger specimens (67% of signal crayfish) that were sexually mature or about to reach sexual maturity. To stop further spread, the method of constructing barriers should be used, which can be applied in the Riksu stream. As a result of fishing for signal crayfish with traps, the population density in all three bodies of water decreased significantly.
The non-native introduced species distribution has spred from all over the world significantly. Due to population increase, the demand for food is also increasing. People are trying to find more economically favorable and reliable solutions, possibilities and alternatives in the cultivation and production of food products. Population migrations, mass transportation of goods around the world, pet trade (including aquarium trade), all of this is the cause of the spread of non-native introduced species. Partly due to people’s ignorance as well as accidental or intentional introduction of species. When a foreign species has found a suitable habitat in a new place, where is not its actual distribution area, then its further spread may cause irreversible damage to ecosystems. In Estonia, Since 2008, the distribution area of three introduced species of crayfish has been registered, which threaten crayfish populations. This is a very serious problem and needs to be addressed as soon as possible (EL 2023/923). The aim of the master’s thesis is to evaluate the impact of fishing carried out in 2022 on signal crayfish (Pacifastacus leniusculus) abundance and longitudinal structure. Of all known possible control methods in Estonia, it is possible to implement only mechanical removal (baited traps). Control fishing was carried out with traps where there were known signal crayfish distribution areas: in Riksu Stream, Reo quarry in Saaremaa, and in Ropka Lake in Tartumaa. As a result of fishing, the population densities of signal crayfish in the distribution areas decreased significantly. To estimate the number of crayfish, the population density estimation scale CPUE (catch per unit effort) is used. The number of crayfish obtained on the night of the trap is divided by the number of traps used in fishing. CPUE decreased by 0.73 units ja Riksu Stream, 0,05 units in Reo quarry, and 0,04 units in Ropka Lake. From specimens removed, more than half (52,7%) were females, which helps to slow down the increase in the number of signal crayfish in the future. During the entire fishing period, catches were dominated by larger specimens (67% of signal crayfish) that were sexually mature or about to reach sexual maturity. To stop further spread, the method of constructing barriers should be used, which can be applied in the Riksu stream. As a result of fishing for signal crayfish with traps, the population density in all three bodies of water decreased significantly.
Kirjeldus
Magistritöö
Kalanduse ja rakendusökoloogia õppekaval
Märksõnad
magistritööd, signaalvähk, väljapüük, võõrvähiliikide tõrje, CPUE, vähipopulatsioonide arvukus