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dc.contributor.authorMohn, Agnes Marie
dc.date.accessioned2018-08-13T15:32:01Z
dc.date.available2018-08-13T15:32:01Z
dc.date.issued2018-06-12
dc.date.submitted2018-06-11T22:00:10Z
dc.identifier.urihttps://hdl.handle.net/1956/18062
dc.description.abstractSea trout are known for seeking out sources of freshwater to rid themselves of salmon lice. Still, the effect of natural haloclines in fjords on parasite dynamics is not well understood. We tagged 48 wild caught sea trout, naturally infested by varying number of lice, with individual depth sensors. The fish were kept inside a small net-pen (4x4x5m) in Western Norway during four periods in spring 2017. The aim was to investigate how trout respond to salmon lice by changing their depth according to a natural halocline, and further elaborate on how this behaviour ultimately impacts their parasite abundance. The results show that temperature and light were the two most important factors explaining the vertical behaviour of trout. Mobile lice also had a significant effect on depth preference, where fish with higher abundances choose to swim shallower. However, individual variation in depth preference was larger than the impact of infestation levels, with some individuals choosing to stay deeper (and more saline) even though they had a high number of lice. There was a substantial reduction in salmon lice abundance during the seven days in the pen (68 ± 58 to 35 ± 18). The number of attached lice declined more rapidly when the temperature was high, most likely because of higher recruitment to mobile stages. Furthermore, the number of mobile lice showed a more substantial reduction when surface salinity was low. Surface salinity explained this reduction better than the experienced salinity of the individual. In summary, the results indicate that short-time exposure to very low salinities, rather than long-term exposure to moderate salinities, is the driving force behind the use of haloclines for delousing purposes.en_US
dc.language.isoengeng
dc.publisherThe University of Bergenen_US
dc.subjectFiskeparasitternob
dc.subjectLakseoppdrettnob
dc.subjectOppdrettslaksnob
dc.titleOptimal response to lousy circumstances: The impact of salmon lice (Lepeophtheirus salmonis) on depth preference of sea trout (Salmo trutta)en_US
dc.typeMaster thesis
dc.date.updated2018-06-11T22:00:10Z
dc.rights.holderCopyright the Author. All rights reserveden_US
dc.description.degreeMasteroppgave i biologien_US
dc.description.localcodeMAMN-BIO
dc.description.localcodeBIO399
dc.subject.realfagstermerhttps://data.ub.uio.no/realfagstermer/c012515
dc.subject.realfagstermerhttps://data.ub.uio.no/realfagstermer/c003776
dc.subject.realfagstermerhttps://data.ub.uio.no/realfagstermer/c012751
dc.subject.nus751999eng
fs.subjectcodeBIO399
fs.unitcode12-60-0


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