Ahvena ( Perca fluviatilis L.) kasvust Eesti väikejärvedes
| dc.contributor.advisor | Krause, Teet | |
| dc.contributor.advisor | Paaver, Tiit | |
| dc.contributor.author | Mandel, Martin | |
| dc.date.accessioned | 2013-05-28T06:20:52Z | |
| dc.date.available | 2013-05-28T06:20:52Z | |
| dc.date.defensed | 2013-05-31 | |
| dc.date.issued | 2013 | |
| dc.description.abstract | Käesoleva töö raames mõõdeti kokku pikkuse tagasiarvutamiseks kindlal aastal 462 ahvena kaaneluud, kellest 339 olid emased ning 122 isased. Valimi koostamisel välditi väikejärvi, mis on koormatud kutseliste kalapüügivahenditega, kuna sarnaselt Matsalu lahe uuringus avaldatud tulemustele (Pukk, 2013) eeldati, et suuremahulisel püügil võib teatud mõju olla ka Eesti väikejärvedes. Töö tulemusena selgus, et Esimese eluaasta lõpuks kasvab ahven Eesti väikejärvede valimis hinnanguliselt keskmiselt 5,8 cm pikkuseks, järgmisel aastal lisandub pikkusele keskmiselt 3,5 cm, kolmandal 3,2 cm ning igal järgneval aastal veel paari millimeetri võrra vähem. Esimesel kolmel eluaastal on kiireim ahvena kasv semidüstroofsetes järvedes ja aeglaseim liigtoitelises järves. Kiirelt süveneva kaldaga orujärved paistsid silma eelkõige ahvenate pikema elueaga. Nii püüti 13 aastased isendid Viljandi järvest ja Soodla järvest Üksiku ahvena pikkuskasvu Eesti väikejärvede valimis kirjeldab pigem sirgjoon ja kasv pidurdub st. muutub kõverjooneks saakloomade puudumisel. Nii pidurdus ahvena pikkuskasv 3.-4. eluaasta vahel Uljaste järves, 5.-6. eluaasta vahel Kahala järves ja 8.-9. eluaasta vahel Kaisma järves, 11.-12. eluaasta vahel Viljandi järves ja 12.-13. eluaasta vahel Soodla veehoidlas. Kaarna ja Kavadi järves oli ahvenate pikkuskasv ühtlik kuni väljapüügini (vanim isend 10 aastane). Kalendriaastate võrdluses kõikus erinevus ahvena hinnangulises keskmises juurdekasvus 0,5 cm piires. Eesti väikejärvede valimis oli emane ahven samas vanusklassis keskmiselt 3,2 mm pikem kui isane ahven. Vanimad isendid valimis olid emased ahvenad. Kokkuvõtlikult võib uuritud materjali põhjal järeldada, et ahvenate kasv Eesti väikejärvedes sõltub nii liigisisesest ja liikidevahelisest konkurentsist, mille olulisust on mainitud ka kirjanduses (Horppila et.al., 2010; Frankiewicz, 2012), kui ka konkreetse järve iseärasutest tingitud teguritest, mille olulisust on samuti varasemate kirjandusallikate põhjal mainitud (Ristkok, 1974; Tolonen, 2003; Horppila et.al., 2010, Estlander et.al., 2010). | est |
| dc.description.abstract | The aim of present study was to examine the growth of perch (perca fluviatilis L.) in small Estoninan inland lakes in order to determine the importance of different biotic and abiotic factors between different waterbodies. In addition, attention was paid on differences in growth between males and females, also on differences between juvenile and mature fish. The fish used in this study were caught from 10 different inland lakes using the scientific gill nets (Nordic-type) and standardized method EVS-EN 14757:2005. After catching, perch were measured (TL,mm) and weighed (TW, g). Also the sex of the fish was determined. Subsequently opercular bones were removed and processed in boiling destilled water, which revealed the rings that characterize the annual growth of perch. Opercular bones were examined in the binocular with the graduated scale and necessary measurements were taken. for back-calculating the growth. The lenghts at each year were calculated as Tln=TLx(Rn/R)b , where Tln was lenght at certain age, TL is lenght measured after catching, Rn is radius from the centre of the bone to the certain age ring, R is overall radius of the opercular and b value represents the ratio between the logarithmic growth rates of the fish and the opercular. In this study the value for b was 0,872, calculated beforehand by Eschbaum (1995). Also the age of individuals was determined. This method for estimating the past growth is widely used in scientific works was first described by Le Cren (1974). In total 462 opercular bones were measured to calculate the growth of the individuals in certain years. From 462 opercular bones 339 were females and 122 were males. To minimize the effect of commercial fishing as was recently described by Pukk (2013), water bodies where commercial fishing took place, were avoided. In data analysis the method of least squares was used. My work revealed following results: At the end of the first year of life the average lenght of perch in small Estonian inland lakes was 5.8 cm, average length after two years was 9,3 cm, after three years, 12,5 cm, and later on the growth rate decreased annually by few millimeters. Increasing nutrient load of water seemed to deminish the growth rate of young perch in first three years of life. Perch lived longer in lakes with rapidly deepening littoral. The oldest fishes (13 years of age) were caught from lake Viljandi and lake Soodla The line describing the individual growth of perch is more likely straight in Estonian inland lakes and becomes curvy as the density of prey fish decreases. So for example the growth of perch slowed down after three years in lake Uljaste and after five to six years in lake Kahala. The average estimated growth rate of perch over all age groups in lakes of this study differed only about 0,5 cm. The average lenght of females in same age groups were 3,2 mm longer than in males The oldest specimens in this study were females. In conclusion, current study showeded that growth of perch in small Estonian inland lakes depended on both – biotic and abiotic factors. More precisely intraspecific and interspecific competition played important roll in growth rate of the fish in different ecosystems. This is also mentioned by other authors ( Horppila et.al., 2010; Frankiewicz, 2012). The features of different lakes (such as water transparency, depth of the waterbody and level of eutrophication) also determined the growth of perch in small Estonian lakes. The fact that the nature of the waterbody influences the growth of individuals has also been mentioned by other authors ( Ristkok, 1974; Tolonen, 2003; Horppila et.al., 2010, Estlander et.al., 2010). | eng |
| dc.identifier.uri | http://hdl.handle.net/10492/905 | |
| dc.subject | ahven | est |
| dc.subject | kasvukiirus | est |
| dc.subject | perca fluviatilis | |
| dc.subject | väikejärved | est |
| dc.subject | magistritööd | est |
| dc.title | Ahvena ( Perca fluviatilis L.) kasvust Eesti väikejärvedes | est |
| dc.title.alternative | Growth of Perch (Perca fluviatilis L.) in small Estonian lakes | eng |
| dc.type | Master Thesis | |
| rioxxterms.freetoread.startdate | ainult raamatukogus | |
| rioxxterms.freetoread.startdate | only in library |
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