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[{"key": "dc.contributor.author", "value": "Myllyl\u00e4, Sonja", "language": null, "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2013-09-11T07:03:26Z", "language": null, "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2013-09-11T07:03:26Z", "language": null, "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2013", "language": null, "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.other", "value": "oai:jykdok.linneanet.fi:1279603", "language": null, "element": "identifier", "qualifier": "other", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/42125", "language": null, "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "It\u00e4meren harmaahylkeiden (Halichoerus grypus) yksil\u00f6m\u00e4\u00e4rien kasvu viime vuosikymmenin\u00e4 on aiheuttanut ristiriitoja ammattikalastajien ja hylkeiden v\u00e4lille. Hylkeiden on todettu muun muassa vahingoittavan pyydyksi\u00e4 ja sy\u00f6v\u00e4n kalastajille arvokasta saalista my\u00f6s pyydyksist\u00e4, kuten lohta (Salmo salar), sek\u00e4 karkottavan kalaparvia kalastusalueiden ulkopuolelle. Toisaalta harmaahylkeille uhkana on hukkuminen pyydyksiin sek\u00e4 lis\u00e4\u00e4ntynyt h\u00e4irint\u00e4 kalastajien ja meriliikenteen toimesta. N\u00e4iden ristiriitojen my\u00f6t\u00e4 kiinnostus hylkeiden ravinnosta on lis\u00e4\u00e4ntynyt. Hylkeiden ravinnonk\u00e4ytt\u00f6\u00e4 on perinteisesti tutkittu ruoansulatuskanavan sis\u00e4ll\u00f6st\u00e4. T\u00e4m\u00e4n menetelm\u00e4n ongelmana on, ett\u00e4 saalislajien sulamattomat j\u00e4\u00e4nteet hylkeen suolistossa kertovat p\u00e4\u00e4asiassa vain sen, mit\u00e4 hylje on sy\u00f6nyt viimeksi. Ravintotutkimusten rinnalle on tullut viime vuosina vakaiden isotooppien -menetelm\u00e4, jonka avulla voidaan arvioida kuluttajan ravintoa pidemm\u00e4lt\u00e4 aikav\u00e4lilt\u00e4. T\u00e4ss\u00e4 pro gradu -tutkielmassa arvioidaan It\u00e4meren harmaahylkeen ravintoa lihaskudoksen hiilen ja typen vakaiden isotooppien (\u03b413C, \u03b415N) avulla. Tutkielmaan valitut viisi saaliskalalajia edustavat eri ravintoverkkotason lajeja: kolmipiikki (Gasterosteus aculeatus) alemman ravintoverkkotason, silakka (Clupea harengus membras), kilohaili (Sprattus sprattus) ja Per\u00e4merell\u00e4 kuore (Osmerus eperlanus) keskitason ravintoverkkotason ja lohi ylemm\u00e4n ravintoverkkotason saalislajeja. Saalislajien suhteellisia osuuksia harmaahylkeen ravinnossa arvioidaan ajallisesti, sukupuolittain ja ik\u00e4ryhmitt\u00e4in kuudella It\u00e4meren eri alueella: Per\u00e4meri, Merenkurkku, Selk\u00e4meri, Saaristomeri, Ahvenanmeri ja Suomenlahti. Tutkielmassa tarkastellaan vakaiden isotooppien (\u03b413C, \u03b415N) avulla harmaahylkeiden ravintoverkkotasojen ja paikallispopulaatioiden muodostumista eri merialueilla. Tulosten perusteella silakka muodosti suuren osan harmaahylkeiden ravinnosta Ahvenanmerell\u00e4 (38 %), Saaristomerell\u00e4 (37 %) ja Suomenlahdella (58 %). Sen sijaan Per\u00e4merell\u00e4 (53 %) ja Selk\u00e4merell\u00e4 (58 %) ravinto koostui lohesta tai muusta merialueen ravintoketjun huipulla olevasta kalalajista. Lohen osuuteen harmaahylkeen ravinnossa on syyt\u00e4 suhtautua varauksella, sill\u00e4 my\u00f6s h\u00e4rk\u00e4simpulla (Myoxocephalus quadricornis) Per\u00e4meren alueella on lohen kaltaiset vakaiden isotooppien (\u03b413C, \u03b415N) arvot. Kilohailin, kuoreen ja kolmipiikin osuudet ravinnosta vaihtelivat 9\u201335 % merialueittain. Ravintoverkkotasot olivat korkeammat etel\u00e4isimmill\u00e4 merialueilla kuin pohjoisilla. Harmaahylkeille mallinnetut populaatiot erosivat merialueittain, joka viittaa paikallispopulaatioiden eroavaisuuksiin vakaiden isotooppien arvoissa. Vaihtelu It\u00e4meren harmaahylkeiden ravinnossa eri merialueiden v\u00e4lill\u00e4 tulisi ottaa huomioon tulevissa tutkimuksissa.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.abstract", "value": "The increasing number of grey seal (Halichoerus grypys) individuals in the Baltic Sea has led to conflicts between commercial fishermen and seals. Grey seals have been perceived to damage fishing nets and take valuable fishes, such as salmon (Salmo salar), directly from the nets, and to chase schools of fish outside the fishing areas. On the other hand the grey seal population is threatened by increased harassment by fishermen and navigation as well as the risk of drowning in fishing gear. These conflicts have increased interest in the diet of grey seals. Seal diets have traditionally been studied from the digestive tract contents. However, a problem with this method is that the prey is digested relatively fast and the indigestible remains of the fish found in the seal gut mainly tells what a seal has last eaten. In recent years a stable isotope method has appeared among traditional dietary studies, which can be used to evaluate consumer food assimilated over a longer time period. This master's thesis explored the diet composition of Baltic grey seals using carbon and nitrogen stable isotope analyses (\u03b413C, \u03b415N) of the seal muscle. In this study we selected five prey fish species which represent different levels of Baltic food webs: three-spined stickleback (Gasterosteus aculeatus) from the lower level of the food web, herring (Clupea harengus membras), sprat (Sprattus sprattus), and smelt (Osmerus eperlanus) from the Bothnian Bay, from the intermediate-level, and finally salmon representing a prey species from the upper level of the food web. Relative proportions of the prey species in the grey seal diet were estimated by season, gender and the age group in six different areas: Bothnian Bay, Quark, Bothnian Sea, Archipelago, \u00c5land Sea and the Gulf of Finland. This research used stable isotopes signatures (\u03b413C, \u03b415N) to estimate how trophic level and local population differ between sea areas. According to the results, herring accounted for a large part of the diet of grey seals in the \u00c5land Sea (38%), in the Archipelago Sea (37%), and the Gulf of Finland (58%). In the Bothnian Bay (53%), and in the Bothnian Sea (58%), the diet consisted more salmon or other fish species from the upper trophic level. The estimated proportion of salmon in the grey seal diet should be viewed with caution, however, as the sculpin (Myoxocephalus quadricornis) in the Bothnian Bay has (\u03b413C and \u03b415N) values similar to those of salmon. Sprat, smelt and three-spined stickleback varied from 9-35% in grey seal diet depending on the sea area. Apparent trophic levels of seals were higher in the southern sea areas than in the northern. Also local populations differ between sea areas based on the stable isotope modelling. Variation in the diet of grey seals in the Baltic Sea between different sea areas should be taken into account in future studies.", "language": "en", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted using Plone Publishing form by Sonja Myllyl\u00e4 (somamyll) on 2013-09-11 07:03:25.785873. Form: Pro gradu -lomake (1 tekij\u00e4) (https://kirjasto.jyu.fi/julkaisut/julkaisulomakkeet/pro-gradu-lomake-1-tekijae). JyX data:", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by jyx lomake-julkaisija (jyx-julkaisija@noreply.fi) on 2013-09-11T07:03:26Z\nNo. of bitstreams: 2\nURN:NBN:fi:jyu-201309112270.pdf: 1348226 bytes, checksum: 0456fbd1c69439752c8eed81731ef159 (MD5)\nlicense.html: 107 bytes, checksum: a7d86e598caa500b1b433bbb9dc8ef1c (MD5)", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2013-09-11T07:03:26Z (GMT). No. of bitstreams: 2\nURN:NBN:fi:jyu-201309112270.pdf: 1348226 bytes, checksum: 0456fbd1c69439752c8eed81731ef159 (MD5)\nlicense.html: 107 bytes, checksum: a7d86e598caa500b1b433bbb9dc8ef1c (MD5)\n Previous issue date: 2013", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "1 verkkoaineisto.", "language": null, "element": "format", "qualifier": "extent", "schema": "dc"}, {"key": "dc.format.mimetype", "value": "application/pdf", "language": null, "element": "format", "qualifier": "mimetype", "schema": "dc"}, {"key": "dc.language.iso", "value": "fin", "language": null, "element": "language", "qualifier": "iso", "schema": "dc"}, {"key": "dc.rights", "value": "In Copyright", "language": "en", "element": "rights", "qualifier": null, "schema": "dc"}, {"key": "dc.subject.other", "value": "harmaahylje", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "lohi", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "silakka", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "ravintoverkkotaso", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "vakaat isotoopit", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "\u03b413C", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "\u03b415N", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "Harmaahylkeen (Halichoerus grypus) ravinto eri osissa pohjoista It\u00e4merta", "language": null, "element": "title", "qualifier": null, "schema": "dc"}, {"key": "dc.type", "value": "master thesis", "language": null, "element": "type", 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null, "element": "date", "qualifier": "updated", "schema": "dc"}, {"key": "dc.type.coar", "value": "http://purl.org/coar/resource_type/c_bdcc", "language": null, "element": "type", "qualifier": "coar", "schema": "dc"}, {"key": "dc.rights.accesslevel", "value": "openAccess", "language": "fi", "element": "rights", "qualifier": "accesslevel", "schema": "dc"}, {"key": "dc.type.publication", "value": "masterThesis", "language": null, "element": "type", "qualifier": "publication", "schema": "dc"}, {"key": "dc.subject.oppiainekoodi", "value": "4012", "language": null, "element": "subject", "qualifier": "oppiainekoodi", "schema": "dc"}, {"key": "dc.subject.yso", "value": "halli", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "hylkeet", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "lohi", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, 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