Decline of the North Sea houting: protective measures for an endangered anadromous fish

Niels Jepsen, Michael Deacon, Anders Koed

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Once an abundant fish species in the rivers of the Wadden Sea in northwest Europe,
the North Sea houting Coregonus oxyrinchus (NSH) was at the brink of extinction 25 yr ago. The
very last stronghold for this species was in the small Danish River Vidaa. In an attempt to preserve
this anadromous whitefish species, juveniles were hatchery-reared and stocked in 6 Danish rivers
flowing into the Wadden Sea. These stocking efforts were fairly successful, and the houting established
populations in at least 2 of the rivers, but the underlying problem of habitat degradation and
migration obstacles was not solved. Since a national management plan was issued in Denmark in
2003, large-scale river restoration measures have been undertaken, including the removal of 13
large obstacles in 3 NSH rivers and reestablishment of meanders in the lower river reaches. These
measures were all intended to increase the spawning area for NSH and reduce juvenile mortality
of NSH. The generic effect of these recent and ongoing changes is, however, not yet known. The
NSH population has been irregularly monitored under various programs. Results from 15 yr of
field investigation using passive integrated transponder (PIT)-tagging showed that the NSH population
in the River Vidaa remains stable, but in the other 2 rivers populations are decreasing.
However, due to the recent physical improvements in river habitat and connectivity, we expect a
substantial improvement in the population status of the NSH in the near future. Once they reach
sexual maturity, NSH grow relatively slowly (mean: 2.55 cm yr−1, ranging from 0 to 13.8 cm yr−1)
and can reach an age of 10 to 12 yr. The number of repeated recaptures year after year indicates
low mortality for adult fish. Six individuals were recaptured in rivers other than the one in which
they were initially PIT-tagged, indicating some exchange/straying between adjacent rivers. Overall
there is a good chance that this unique species was saved in the 11th hour by intervention from
managers and the EU
Original languageEnglish
JournalEndangered Species Research
Volume16
Pages (from-to)77-84
ISSN1863-5407
DOIs
Publication statusPublished - 2012

Cite this

@article{6dff6f9229c743c19ba4d6ae70a4005f,
title = "Decline of the North Sea houting: protective measures for an endangered anadromous fish",
abstract = "Once an abundant fish species in the rivers of the Wadden Sea in northwest Europe, the North Sea houting Coregonus oxyrinchus (NSH) was at the brink of extinction 25 yr ago. The very last stronghold for this species was in the small Danish River Vidaa. In an attempt to preserve this anadromous whitefish species, juveniles were hatchery-reared and stocked in 6 Danish rivers flowing into the Wadden Sea. These stocking efforts were fairly successful, and the houting established populations in at least 2 of the rivers, but the underlying problem of habitat degradation and migration obstacles was not solved. Since a national management plan was issued in Denmark in 2003, large-scale river restoration measures have been undertaken, including the removal of 13 large obstacles in 3 NSH rivers and reestablishment of meanders in the lower river reaches. These measures were all intended to increase the spawning area for NSH and reduce juvenile mortality of NSH. The generic effect of these recent and ongoing changes is, however, not yet known. The NSH population has been irregularly monitored under various programs. Results from 15 yr of field investigation using passive integrated transponder (PIT)-tagging showed that the NSH population in the River Vidaa remains stable, but in the other 2 rivers populations are decreasing. However, due to the recent physical improvements in river habitat and connectivity, we expect a substantial improvement in the population status of the NSH in the near future. Once they reach sexual maturity, NSH grow relatively slowly (mean: 2.55 cm yr−1, ranging from 0 to 13.8 cm yr−1) and can reach an age of 10 to 12 yr. The number of repeated recaptures year after year indicates low mortality for adult fish. Six individuals were recaptured in rivers other than the one in which they were initially PIT-tagged, indicating some exchange/straying between adjacent rivers. Overall there is a good chance that this unique species was saved in the 11th hour by intervention from managers and the EU",
author = "Niels Jepsen and Michael Deacon and Anders Koed",
year = "2012",
doi = "10.3354/esr00386",
language = "English",
volume = "16",
pages = "77--84",
journal = "Endangered Species Research",
issn = "1863-5407",
publisher = "Inter Research",

}

Decline of the North Sea houting: protective measures for an endangered anadromous fish. / Jepsen, Niels; Deacon, Michael; Koed, Anders.

In: Endangered Species Research, Vol. 16, 2012, p. 77-84.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Decline of the North Sea houting: protective measures for an endangered anadromous fish

AU - Jepsen, Niels

AU - Deacon, Michael

AU - Koed, Anders

PY - 2012

Y1 - 2012

N2 - Once an abundant fish species in the rivers of the Wadden Sea in northwest Europe, the North Sea houting Coregonus oxyrinchus (NSH) was at the brink of extinction 25 yr ago. The very last stronghold for this species was in the small Danish River Vidaa. In an attempt to preserve this anadromous whitefish species, juveniles were hatchery-reared and stocked in 6 Danish rivers flowing into the Wadden Sea. These stocking efforts were fairly successful, and the houting established populations in at least 2 of the rivers, but the underlying problem of habitat degradation and migration obstacles was not solved. Since a national management plan was issued in Denmark in 2003, large-scale river restoration measures have been undertaken, including the removal of 13 large obstacles in 3 NSH rivers and reestablishment of meanders in the lower river reaches. These measures were all intended to increase the spawning area for NSH and reduce juvenile mortality of NSH. The generic effect of these recent and ongoing changes is, however, not yet known. The NSH population has been irregularly monitored under various programs. Results from 15 yr of field investigation using passive integrated transponder (PIT)-tagging showed that the NSH population in the River Vidaa remains stable, but in the other 2 rivers populations are decreasing. However, due to the recent physical improvements in river habitat and connectivity, we expect a substantial improvement in the population status of the NSH in the near future. Once they reach sexual maturity, NSH grow relatively slowly (mean: 2.55 cm yr−1, ranging from 0 to 13.8 cm yr−1) and can reach an age of 10 to 12 yr. The number of repeated recaptures year after year indicates low mortality for adult fish. Six individuals were recaptured in rivers other than the one in which they were initially PIT-tagged, indicating some exchange/straying between adjacent rivers. Overall there is a good chance that this unique species was saved in the 11th hour by intervention from managers and the EU

AB - Once an abundant fish species in the rivers of the Wadden Sea in northwest Europe, the North Sea houting Coregonus oxyrinchus (NSH) was at the brink of extinction 25 yr ago. The very last stronghold for this species was in the small Danish River Vidaa. In an attempt to preserve this anadromous whitefish species, juveniles were hatchery-reared and stocked in 6 Danish rivers flowing into the Wadden Sea. These stocking efforts were fairly successful, and the houting established populations in at least 2 of the rivers, but the underlying problem of habitat degradation and migration obstacles was not solved. Since a national management plan was issued in Denmark in 2003, large-scale river restoration measures have been undertaken, including the removal of 13 large obstacles in 3 NSH rivers and reestablishment of meanders in the lower river reaches. These measures were all intended to increase the spawning area for NSH and reduce juvenile mortality of NSH. The generic effect of these recent and ongoing changes is, however, not yet known. The NSH population has been irregularly monitored under various programs. Results from 15 yr of field investigation using passive integrated transponder (PIT)-tagging showed that the NSH population in the River Vidaa remains stable, but in the other 2 rivers populations are decreasing. However, due to the recent physical improvements in river habitat and connectivity, we expect a substantial improvement in the population status of the NSH in the near future. Once they reach sexual maturity, NSH grow relatively slowly (mean: 2.55 cm yr−1, ranging from 0 to 13.8 cm yr−1) and can reach an age of 10 to 12 yr. The number of repeated recaptures year after year indicates low mortality for adult fish. Six individuals were recaptured in rivers other than the one in which they were initially PIT-tagged, indicating some exchange/straying between adjacent rivers. Overall there is a good chance that this unique species was saved in the 11th hour by intervention from managers and the EU

U2 - 10.3354/esr00386

DO - 10.3354/esr00386

M3 - Journal article

VL - 16

SP - 77

EP - 84

JO - Endangered Species Research

JF - Endangered Species Research

SN - 1863-5407

ER -