Aarestrup, Kim

Birnie-Gauvin, Kim

Kristensen, Martin Lykke

Sivebæk, Finn

Almost all surviving acoustically tagged sea trout smolts and kelts left a Danish fjord system using a similar 120 km long route. They also left with the highest recorded progression speed ever reported for sea trout in the literature. The repeatability of the behaviour and the geographical history of the Limfjord suggest that the sea trout are adapted to the specific conditions found in the area

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Downloaded from orbit.dtu.dk on: Sep 11, 2019Sea trout behaviour in the Limfjord - a fascinating display of the adaptability of thespecies?Kristensen, Martin Lykke; Birnie-Gauvin, Kim; Aarestrup, Kim; Sivebæk, FinnPublication date:2019Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Kristensen, M. L., Birnie-Gauvin, K., Aarestrup, K., & Sivebæk, F. (2019). Sea trout behaviour in the Limfjord - afascinating display of the adaptability of the species? Technical University of Denmark (DTU). Fiskepleje.dkAlmost all surviving acoustically tagged sea trout smolts and kelts left a Danish fjordsystem using a similar 120 km long route.  They also left with the highest recordedprogression speed ever reported for sea trout in the literature. The repeatability of thebehaviour and the geographical history of the Limfjord suggest that the sea trout areadapted to the specific conditions found in the area.The Limfjord is the longest fjord in Denmark, crossing the entire width of the Jutland peninsula. Some of themost important Danish sea trout rivers exit into the fjord. To complete their marine stage, the fish can remainwithin the fjord, or migrate to sea. If they migrate to sea, the fish can exit the fjord through both a Westernexit into the North Sea and an Eastern exit into the Kattegat Sea. Two recent studies have investigated themigration of smolts and kelts from two of the largest rivers exiting into the central part of the fjord, with theaim of exploring their behaviour and survival in the fjord. Is the Limfjord home to some ‘fjord residents’? Ifnot, which exit will the fish use?The results were obtained by tagging 101 smolts and 160 kelts from River Karup and River Simested withacoustic tags, and following their migration with Automatic Listening Stations strategically placed throughoutthe fjord. The fish from the two river systems behaved similarly in the fjord despite the river outlets beinglocated roughly 35 km apart. Survival in the fjord was low. After a short period of residency near the rivermouths, the vast majority (98 %) of the surviving fish migrated the 120 km to the Kattegat Sea through theEastern exit within a narrow window of time. Only 2 % of kelts (n = 2) stayed in the fjord (none of the smoltsdid so), and no fish left the fjord using the 110 km long (and thus shorter) western route to the North Sea.Notably, this route has only existed since 1825, when a storm opened the Limfjord to the North Sea. Thekelts spent a mean of 4.5 days (range: 2.8 – 11.6 days) migrating through the final 103 km of the fjord, withmean progression rates increasing to 43.6 km d  (range: 10 - 86 km d ) in the narrow final 29 km beforereaching the sea.  This is the highest linear progression rates ever reported for sea trout in the scientificliterature.The observed sea trout-behaviour in the Limfjord system is unique compared to observations in fjordsystems elsewhere. Sea trout have been documented to stay close to the river mouth throughout their-1 -1FORSIDE ENGLISH SEA TROUT BEHAVIOUR IN THE LIMFJORDCookiesSea trout behaviour in the Limfjord - a fascinating display of the adapta... https://www.fiskepleje.dk/service/english_version_fiskepleje/sea-trout...1 af 2 14-08-2019 12:35Opdateret af Finn Sivebæk den 14. august 2019marine period in several other systems, but the Limfjord could be a dangerous place to exhibit this strategy.Our results reveal that only 20 % of the smolts had survived their trip through the Limfjord, and 64 % of thekelts that entered the Limfjord ended up dying or being lost in it. The cost of residing in the Limfjord thereforeappears high. The relatively constant, fast and highly directed movement recorded for both smolts and keltsfrom the two different river systems in our study could reflect important local adaptations to survive in thisdangerous fjord. Previous studies with genetic methods have documented that non-native sea trout stockedin the region during the 20th century failed to survive in the Limfjord, possibly as a consequence of them notbeing adapted to these unique local conditions the way that wild fish are.Our results therefore highlight the potential adaptability and behavioural flexibility of sea trout in marineenvironments, and further demonstrate the importance of conditions in the marine environment for thesurvival and behaviour of sea trout.Smolt behaviour and survival in the LimfjordKelt behaviour and survival in the LimfjordAf Martin Lykke Kristensen, Kim Birnie-Gauvin, Kim Aarestrup and Finn Sivebæk, DTU Aqua, Institut forAkvatiske Ressourcer.https://www.fiskepleje.dk/service/english_version_fiskepleje/sea-trout-behaviour-in-the-limfjord14 AUGUST 2019CookiesSea trout behaviour in the Limfjord - a fascinating display of the adapta... https://www.fiskepleje.dk/service/english_version_fiskepleje/sea-trout...2 af 2 14-08-2019 12:35

Sea trout behaviour in the Limfjord - a fascinating display of the adaptability of the species?

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Sea trout behaviour in the Limfjord - a fascinating display of the adaptability of the species?

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