Getting cosy in freshwater: assumed-to-be brackish pike are not so brackish after all

Kim Birnie-Gauvin*, Lasse Birch Højrup, Theis Kragh, Lene Jacobsen, Kim Aarestrup

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.
Original languageEnglish
JournalEcology of Freshwater Fish
Volume28
Issue number3
Pages (from-to)376-384
ISSN0906-6691
DOIs
Publication statusPublished - 2018

Keywords

  • Brackish
  • Ecosystem functioning
  • Esox lucius
  • Freshwater
  • Reproductive migrations

Cite this

Birnie-Gauvin, Kim ; Højrup, Lasse Birch ; Kragh, Theis ; Jacobsen, Lene ; Aarestrup, Kim. / Getting cosy in freshwater: assumed-to-be brackish pike are not so brackish after all. In: Ecology of Freshwater Fish. 2018 ; Vol. 28, No. 3. pp. 376-384.
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title = "Getting cosy in freshwater: assumed-to-be brackish pike are not so brackish after all",
abstract = "Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.",
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author = "Kim Birnie-Gauvin and H{\o}jrup, {Lasse Birch} and Theis Kragh and Lene Jacobsen and Kim Aarestrup",
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Getting cosy in freshwater: assumed-to-be brackish pike are not so brackish after all. / Birnie-Gauvin, Kim; Højrup, Lasse Birch; Kragh, Theis; Jacobsen, Lene; Aarestrup, Kim.

In: Ecology of Freshwater Fish, Vol. 28, No. 3, 2018, p. 376-384.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Getting cosy in freshwater: assumed-to-be brackish pike are not so brackish after all

AU - Birnie-Gauvin, Kim

AU - Højrup, Lasse Birch

AU - Kragh, Theis

AU - Jacobsen, Lene

AU - Aarestrup, Kim

PY - 2018

Y1 - 2018

N2 - Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.

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