D4 Published development or research report or study
Rehabilitation of two northern river lamprey (Lampetra fluviatilis) populations impacted by various anthropogenic pressures : lessons learnt in the past three decades (2019)

Aronsuu, K., Vikström, R., Marjomäki, T. J., Wennman, K., Pakkala, J., Mäenpää, E., Tuohino, J., Sarell, J., & Ojutkangs, E. (2019). Rehabilitation of two northern river lamprey (Lampetra fluviatilis) populations impacted by various anthropogenic pressures : lessons learnt in the past three decades. University of Jyväskylä. Jyväskylän yliopiston bio- ja ympäristötieteiden laitoksen tiedonantoja, 2/2019. https://doi.org/10.17011/jyx/18282/64592

JYU authors or editors

Publication details

All authors or editors: Aronsuu, Kimmo; Vikström, Risto; Marjomäki, Timo J.; Wennman, Kim; Pakkala, Jukka; Mäenpää, Eero; Tuohino, Jukka; Sarell, Juha; Ojutkangs, Esa

eISBN: 978-951-39-7801-3

Journal or series: Jyväskylän yliopiston bio- ja ympäristötieteiden laitoksen tiedonantoja

ISSN: 1795-6900

eISSN: 2669-8986

Publication year: 2019

Number in series: 2/2019

Number of pages in the book: 52

Publisher: University of Jyväskylä

Publication country: Finland

Publication language: English

DOI: https://doi.org/10.17011/jyx/18282/64592

Persistent website address: http://urn.fi/URN:ISBN:978-951-39-7801-3

Publication open access: Openly available

Publication channel open access: Open Access channel

Abstract

The pioneering work done during the past three decades in the regulated Rivers Perhonjoki and Kalajoki, Finland, to study and rehabilitate river lamprey populations is presented. The effects of various anthropogenic activities and rehabilitation measures are evaluated based on habitat surveys and long-term monitoring of larval densities, numbers of adults migrating upstream and of transformers migrating downstream. Telemetric tracking and tagging experiments were used to determine the efficacy of fishways. Lamprey populations in both rivers decreased in the 1980s and 1990s. This was linked to obstructed upstream migration of adults and deterioration of habitats for different life stages due to various regulation measures and hydropeaking. In the River Perhonjoki, 571 000 adult lampreys were translocated above the migration barriers in 1981–2010 and 247 million sub-yearling larvae were stocked in 1997–2010 of regulation. Furthermore, attempts were made to restore key habitats in various river sections, hydropeaking was mitigated and a fishway complex was constructed. Despite these mitigation measures, the river lamprey population has not recovered. In the River Kalajoki, a fish ramp was constructed to enhance migration over a weir and lampreys passed through it effectively. Further, fast-flowing areas were restored with lamprey-specific methods. After restoration the densities of both sub-yearling and older larvae increased, but despite the mitigation measures, larval densities in the river section just below the hydroelectric power plant remained at a low level. Possible mechanisms by which different anthropogenic activities affect different life stages of river lamprey and possible reasons for inefficacy or efficacy of rehabilitation measures are discussed.

Keywords: living environment; introduction (animals); fishways; restoration (repairing); Lampetra fluviatilis; hydraulic construction

Free keywords: lyhytaikaissäännöstely; dredging; erosion; habitat management; hydropower recovery; fish; river

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2019