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Brage IMR
Report . 2000
Data sources: Brage IMR
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Kartlegging av gyteplasser og sonderende oksygenmålinger i utvalgte fjorder i Risør, Tvedestrand og Lillesand kommune

Authors: Knutsen, Jan Atle; Bergstad, Odd Aksel; Gjøsæter, Jakob; Enersen, Svein Erik; Omli, Lena;

Kartlegging av gyteplasser og sonderende oksygenmålinger i utvalgte fjorder i Risør, Tvedestrand og Lillesand kommune

Abstract

This pilot project was initiated to compile and map old fishermen's local information on spawning areas of cod and other commercial fishes along the Norwegian Skagerrak Coast. Interviews revealed that fishermen had good knowledge of spawning areas, especially of cod, mainly based on their own experiences from fishing mature cod in the fjords in winter. Numerous spawning sites were localized exactly and consistently, and several sources supplied qualified information about the distribution and abundance of spawning fish over the last 50 years. In general, a gradual reduction in abundance of spawning fish was suggested, especially since the 1970s. Over-fishing was considered the main threat to the spawning population of cod. However, many sources also claimed that productive and important spawning areas still occur in many areas. Surveys in the spawning areas showed high oxygen levels, except in deep localities in the more enclosed fjords. Deeper parts of the inner fjords, and also deeper parts of some coastal basins had oxygen levels considered below limits acceptable to cod. The project was finansially supported by the County Governor of Aust-Agder. NORSK SAMMENDRAG: Gyteplasser for torsk, og andre kommersielle fiskeslag i utvalgte fjorder og kystnære farvann i Risør, Tvedestrand og Lillesand kommune er kartlagt ut i fra opplysninger innhentet i intervjuer med eldre kystfiskere. Intervjuundersøkelsen viser at eldre kystfiskere har god kunnskap om gyteplasser for torsk, men også i noen tilfelle for lyr og enkelte andre fiskeslag. Flere har selv deltatt i vinterfiske etter gytemoden torsk, et fiske som fremdeles pågår. Kartleggingen er ikke fullstendig, men en del gyteområder er likevel klart og konsist lokalisert. Selv om det foreløpig ikke er utført rettede fiskeforsøk som kunne gi uavhengig informasjon, er de muntlig overleverte opplysningene verdifulle både for forskning og forvaltning. Informasjonen som her legges frem bør tas med i den fylkeskommunale og kommunale planleggingen, dvs inngå i kommunenes kystsoneplaner, fylkesdelplaner for kystsonen mv. Kildepersonene vurderer dagens gytebestand av kysttorsk i fjordene som langt svakere enn tidligere, men mener dog at mange områder fremdeles har gode gytebestander. Oksygenundersøkelsene foretatt innen noen av de anviste gyteområdene i gytetiden, viste stort sett gode oksygenforhold unntatt i dypere vannlag på de innerste målestasjonene. Publiserte undersøkelser fra Skagerrakkysten har rapportert om såvidt lave oksygennivåer i dypere vannlag i fjordene og kystbassengene at store vannvolum i deler av året ikke vil være aktuelle habitater for gytefisk, ei heller for larver og yngel. Hvorvidt dette vil ha betydning for bestandsutviklingen av torsk langs kysten er det for tidlig å si noe eksakt om, men det vil fortsatt være viktig å overvåke vannmassene mht oksygenmetningsnivå i årene fremover. Forstudiet konkluderer også med at det for torskefisket bør foretas en beskatningstudie for å klarlegge den relative betydning av ulike beskatningsformer og -aktører. Arbeidet har hatt økonomisk støtte fra Fylkesmannen i Aust-Agder, miljøvernavdelingen.

Country
Norway
Related Organizations
Keywords

oxygen level, torsk, oksygennivå, spawning areas, cod, kystsoneforvaltning, gyteplasser, coastal management

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    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
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    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    Average
    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Average
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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average
Green