Doctoral Dissertation

8.5. M.Sc. Kimmo Aronsuu (Faculty of Mathematics and Science, Aquatic Sciences)

M.Sc. Kimmo Aronsuu defends his doctoral dissertation in Aquatic Sciences ”Lotic life stages of the Eu­ropean river lamprey (Lampetra fluviatilis): anthropogenic detriment and rehabilitation”. Dr. Opponent Martyn Lucas (Durham University, UK) and custos Adjunct Professor Timo Marjomäki (University of Jyväskylä).

Kimmo AronsuuM.Sc. Kimmo Aronsuu defends his doctoral dissertation in Aquatic Sciences ”Lotic life stages of the Eu­ropean river lamprey (Lampetra fluviatilis): anthropogenic detriment and rehabilitation”. Dr. Opponent Martyn Lucas (Durham University, UK) and custos Adjunct Professor Timo Marjomäki (University of Jyväskylä).

The goal of this study was to increase knowledge about the migratory behaviour of adult river lampreys and the habitat of riverine life stages of river lamprey. Furthermore, the detrimental effects of various anthropogenic activities on lamprey populations and the efficacy of different rehabilitation measures were evaluated over three decades of monitoring the development of river lamprey populations in two intensively regulated northern rivers. River discharge, illumination by the moon, wind conditions and water temperature all affected the migratory activity of upstream migrating adults, while artificial lighting may create illumination barriers for migration. A natural-like fish ramp was observed to enhance passage over low-head barriers. During the winter holding period, adult lampreys preferred glides, runs and the lowermost parts of riffles with substratum dominated by large boulders (> 256 mm). River lampreys may use a wide variety of gravel sizes for spawning, and flow conditions had an effect on spawning substratum selection. When lamprey larvae reached a total length (TL) of 8 mm they started to select substrata which enabled them to construct a burrow, while the smaller larvae favoured substrata containing holes. Natural gravel with fine material was frequently selected as a burrowing substratum by sub-yearling lampreys with TL > 8 mm. The larvae older than one year rejected clay bottoms. The main results from the monitored field populations suggested that river regulation measures drastically reduced river lamprey habitats and populations. Translocations of adult lampreys did not necessarily compensate for the negative effects of obstructed migration, but insufficient number of translocated adults, habitat degradation or increased predation may lead to reduced population size. Stocking with sub-yearling larvae was an appropriate method for reintroduction of a lamprey population. River restoration may enhance the recovery of river the lamprey population in a short-term regulated river.


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Kimmo Aronsuu