{"id":{"repo_id":"u-iceland","oai_identifier":"oai:skemman.is:1946/50304"},"canonical_url":"https://search.dev.ndltd.org/etd/u-iceland/oai:skemman.is:1946/50304","repository":{"repo_id":"u-iceland","name":"University of Iceland","base_url":"https://skemman.is/oai/request"},"display":{"title":"Parasite abundance in Atlantic cod (Gadus morhua) in shallow and deep waters around Iceland","abstract":"Proper stock identification of atlantic cod (Gadus morhua) is necessary in modern Icelandic fisheries management to ensure that stocks of cod are not overfished. Today the cod fishery in Iceland is treated as a single stock but studies have shown that there might in fact be two. In addition to there being possibly two stocks there are also coastal and frontal ecotypes which inhabit different depths during the feeding season. Today these ecotypes are detected by molecular sequencing but here I show that parasites as biological tags might be a useful method in cod ecotype identification since results indicate that there is variation in parasite infection between the coastal and frontal types. I found that certain groups of parasites like copepods, nematodes and acanthocephalans appear to infect the ecotypes differently in terms of abundance and diversity of parasites. Deep-water cod had a mean abundance of 95.2 (SD = 68.4) nematodes, 2.2 (SD = 2.17) acanthocephalans and 3.8 (SD = 3.7) copepods. Shallow-water cod had a mean abundance of 72.1 (SD = 70.07) nematodes, 0.8 (SD = 1.08) acanthocephalans and 3.73 (SD = 3.67) copepods. Certain sites of infection showed interesting patterns of infection, but more research is needed before a parasite species can be chosen as a biological tag. These results support the use of parasites as biological tags for use of ecotype discrimination.","abstract_html":"Proper stock identification of atlantic cod (Gadus morhua) is necessary in modern Icelandic fisheries management to ensure that stocks of cod are not overfished. Today the cod fishery in Iceland is treated as a single stock but studies have shown that there might in fact be two. In addition to there being possibly two stocks there are also coastal and frontal ecotypes which inhabit different depths during the feeding season. Today these ecotypes are detected by molecular sequencing but here I show that parasites as biological tags might be a useful method in cod ecotype identification since results indicate that there is variation in parasite infection between the coastal and frontal types. I found that certain groups of parasites like copepods, nematodes and acanthocephalans appear to infect the ecotypes differently in terms of abundance and diversity of parasites. Deep-water cod had a mean abundance of 95.2 (SD = 68.4) nematodes, 2.2 (SD = 2.17) acanthocephalans and 3.8 (SD = 3.7) copepods. Shallow-water cod had a mean abundance of 72.1 (SD = 70.07) nematodes, 0.8 (SD = 1.08) acanthocephalans and 3.73 (SD = 3.67) copepods. Certain sites of infection showed interesting patterns of infection, but more research is needed before a parasite species can be chosen as a biological tag. These results support the use of parasites as biological tags for use of ecotype discrimination.","abstract_has_math":false,"creators":["Magnús Máni Dagsson 1997-"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Háskóli Íslands"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-05-21T11:27:48Z","date_published":"2025-05-21T11:27:48Z","updated_at":"2026-07-27T21:37:05Z","subjects":["Líffræði"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1946/50304","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Háskóli Íslands"]},{"key":"dc:creator","label":"Author","values":["Magnús Máni Dagsson 1997-"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-05-21T11:27:48Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-05-21T11:27:48Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-05-21T11:27:48Z"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Líffræði"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/1946/50304"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Proper stock identification of atlantic cod (Gadus morhua) is necessary in modern Icelandic fisheries management to ensure that stocks of cod are not overfished. Today the cod fishery in Iceland is treated as a single stock but studies have shown that there might in fact be two. In addition to there being possibly two stocks there are also coastal and frontal ecotypes which inhabit different depths during the feeding season. Today these ecotypes are detected by molecular sequencing but here I show that parasites as biological tags might be a useful method in cod ecotype identification since results indicate that there is variation in parasite infection between the coastal and frontal types. I found that certain groups of parasites like copepods, nematodes and acanthocephalans appear to infect the ecotypes differently in terms of abundance and diversity of parasites. Deep-water cod had a mean abundance of 95.2 (SD = 68.4) nematodes, 2.2 (SD = 2.17) acanthocephalans and 3.8 (SD = 3.7) copepods. Shallow-water cod had a mean abundance of 72.1 (SD = 70.07) nematodes, 0.8 (SD = 1.08) acanthocephalans and 3.73 (SD = 3.67) copepods. Certain sites of infection showed interesting patterns of infection, but more research is needed before a parasite species can be chosen as a biological tag. These results support the use of parasites as biological tags for use of ecotype discrimination.","Almennilegt mat á nytjastofni atlantshafsþorsk er nauðsynlegt í nútímalegri Íslenskri fiskveiðistjórnun til þess að sjá til þess að nytjastofnar þorsk eru ekki ofveiddir. Í dag í þorskastofn Íslands meðhöndlaður sem einn nytjastofn en rannsóknir hafa sýnt að þeir gætu í raun verið tveir. Til viðbótar við það að það séu mögulega tveir nytjastofna á þá er líka til strand og útsjávar staðbrigði sem búa við mismunandi dýptir á fóðurtímabilinu. Í dag er þessi staðbrigði greind með því að nota sameinda raðgreiningu en í þessari rannsóknum sýni ég fram á að sníkjudýr sem líffræðileg merki gætu verið gagnleg aðferð í stafbrigða aðgreiningu þar sem niðurstöðurnar sýna að það sé breytileiki í sníkjudýra sýkingum á milli staðbrigðanna tveggja. Ég fann að sumir hópar sníkjudýra eins og krabbaflær, þráðormar og krókhöfðar virðast sýkja staðbrigðin mismunandi hvað varðar gnægð og fjölbreytileika sníkjudýra. Djúpsjávar þorskur var með meðal gnægð af 95,2 (SF = 68.4) þráðormum, 2,2 (SF = 2,17) krókhöfðum og 3,8 (SF = 3,7) krabbaflær. Grunnsævis þorskur var með meðal gnægð af 72,1 (SF = 70,07) þráðormum, 0,8 (SF = 1,08) krókhöfðum og 3,73 (SF = 3,67) krabbaflær. Sumir sýkingarstaðir sýndu áhugaverð sýkingarmynstur, en þörf er á meiri rannsóknum áður en sníkjudýrategund getur verið valin sem líffræðilegt merki. Þessar niðurstöður styðja við notkun sníkjudýra sem líffræðileg merki fyrir staðbrigða aðgreiningu."]},{"key":"dc:title","label":"Title","values":["Parasite abundance in Atlantic cod (Gadus morhua) in shallow and deep waters around Iceland","Sníkjudýra gnægð í Atlantshafsþorski (Gadus morhua) í grunnum og djúpum sjó í kringum Ísland"]}]}],"canonical_facts":{"dc:contributor":["Háskóli Íslands"],"dc:creator":["Magnús Máni Dagsson 1997-"],"dc:date.accessioned":["2025-05-21T11:27:48Z"],"dc:date.available":["2025-05-21T11:27:48Z"],"dc:date.issued":["2025-05-21T11:27:48Z"],"dc:description.abstract":["Proper stock identification of atlantic cod (Gadus morhua) is necessary in modern Icelandic fisheries management to ensure that stocks of cod are not overfished. Today the cod fishery in Iceland is treated as a single stock but studies have shown that there might in fact be two. In addition to there being possibly two stocks there are also coastal and frontal ecotypes which inhabit different depths during the feeding season. Today these ecotypes are detected by molecular sequencing but here I show that parasites as biological tags might be a useful method in cod ecotype identification since results indicate that there is variation in parasite infection between the coastal and frontal types. I found that certain groups of parasites like copepods, nematodes and acanthocephalans appear to infect the ecotypes differently in terms of abundance and diversity of parasites. Deep-water cod had a mean abundance of 95.2 (SD = 68.4) nematodes, 2.2 (SD = 2.17) acanthocephalans and 3.8 (SD = 3.7) copepods. Shallow-water cod had a mean abundance of 72.1 (SD = 70.07) nematodes, 0.8 (SD = 1.08) acanthocephalans and 3.73 (SD = 3.67) copepods. Certain sites of infection showed interesting patterns of infection, but more research is needed before a parasite species can be chosen as a biological tag. These results support the use of parasites as biological tags for use of ecotype discrimination.","Almennilegt mat á nytjastofni atlantshafsþorsk er nauðsynlegt í nútímalegri Íslenskri fiskveiðistjórnun til þess að sjá til þess að nytjastofnar þorsk eru ekki ofveiddir. Í dag í þorskastofn Íslands meðhöndlaður sem einn nytjastofn en rannsóknir hafa sýnt að þeir gætu í raun verið tveir. Til viðbótar við það að það séu mögulega tveir nytjastofna á þá er líka til strand og útsjávar staðbrigði sem búa við mismunandi dýptir á fóðurtímabilinu. Í dag er þessi staðbrigði greind með því að nota sameinda raðgreiningu en í þessari rannsóknum sýni ég fram á að sníkjudýr sem líffræðileg merki gætu verið gagnleg aðferð í stafbrigða aðgreiningu þar sem niðurstöðurnar sýna að það sé breytileiki í sníkjudýra sýkingum á milli staðbrigðanna tveggja. Ég fann að sumir hópar sníkjudýra eins og krabbaflær, þráðormar og krókhöfðar virðast sýkja staðbrigðin mismunandi hvað varðar gnægð og fjölbreytileika sníkjudýra. Djúpsjávar þorskur var með meðal gnægð af 95,2 (SF = 68.4) þráðormum, 2,2 (SF = 2,17) krókhöfðum og 3,8 (SF = 3,7) krabbaflær. Grunnsævis þorskur var með meðal gnægð af 72,1 (SF = 70,07) þráðormum, 0,8 (SF = 1,08) krókhöfðum og 3,73 (SF = 3,67) krabbaflær. Sumir sýkingarstaðir sýndu áhugaverð sýkingarmynstur, en þörf er á meiri rannsóknum áður en sníkjudýrategund getur verið valin sem líffræðilegt merki. Þessar niðurstöður styðja við notkun sníkjudýra sem líffræðileg merki fyrir staðbrigða aðgreiningu."],"dc:identifier.uri":["https://hdl.handle.net/1946/50304"],"dc:language.iso":["en"],"dc:subject":["Líffræði"],"dc:title":["Parasite abundance in Atlantic cod (Gadus morhua) in shallow and deep waters around Iceland","Sníkjudýra gnægð í Atlantshafsþorski (Gadus morhua) í grunnum og djúpum sjó í kringum Ísland"],"dc:type":["Thesis"]},"updated_at":"2026-07-27T21:37:05Z"}