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Individual movement variation in upstream-migrating sea lamprey Petromyzon marinus in a highly fragmented river

Davies, Peter; Britton, John Robert; Nunn, Andrew D.; Dodd, Jamie R.; Bainger, Chris; Velterop, Randolph; Bolland, Jonathan D.


Peter Davies

John Robert Britton

Chris Bainger

Randolph Velterop


Anthropogenic reductions in riverine connectivity can severely impede the migrations of anadromous species. In fragmented rivers, successful migrations depend on the ability of migrants to negotiate barriers or locate alternative passage routes. However, individual variation in the specific aspects of movement that determine migration success in fragmented rivers, is poorly characterised. Here, individual variation was investigated in the spawning migrations of 56 adult sea lamprey Petromyzon marinus, an anadromous, semelparous species that does not show fidelity to natal rivers. The variability and consequences of two key aspects of fish migration within fragmented rivers were tested: passage time (total time taken to pass a barrier) and retreats (exploratory downstream movements after unsuccessful passage attempts). These were tested using acoustic telemetry in the highly fragmented River Severn catchment, western England, U.K. Distinct unimodal, bimodal, and multimodal patterns of variation in passage times were displayed across the different barriers, potentially related to the physical characteristics of the barrier and prevailing river discharge conditions when the barriers were first approached, but were not related to lamprey body sizes. At the first three barriers encountered by upstream-migrating sea lamprey in the study, between 30% and 46% of individuals made retreat movements, and between 5% and 100% of retreating individuals were able to locate alternative tributaries. Retreating individuals were highly variable in their distance and frequency of retreats; overall, retreat movements comprised 11% (lower-upper quartiles 0%–52%, range 0%–76%) of the total distance moved before reaching spawning areas. Time-to-event analysis indicated that retreat rates reduced as river discharge increased. There was no evidence indicating that individual variation in passage time, or presence of retreat movements at barriers, influenced the subsequent upstream migration speed or final upstream extent of lampreys. While predictability in rank arrival timing was high within three unobstructed reaches, this predictability was disrupted at barriers due to individual variation in passage times. Anthropogenic barriers thus can both disrupt and reveal individual variation in the migration dynamics of anadromous species. Substantial variability in retreat behaviours can be displayed by anadromous species facing delays at barriers, with these behaviours also associated with environmental conditions and the availability of alternative migration routes. Individual variation in exploration and passage time of migrants strongly influence their eventual spawning distribution.


Davies, P., Britton, J. R., Nunn, A. D., Dodd, J. R., Bainger, C., Velterop, R., & Bolland, J. D. (in press). Individual movement variation in upstream-migrating sea lamprey Petromyzon marinus in a highly fragmented river. Freshwater biology,

Journal Article Type Article
Acceptance Date Dec 2, 2021
Online Publication Date Jan 21, 2022
Deposit Date Jan 22, 2022
Publicly Available Date Jan 22, 2023
Journal Freshwater Biology
Print ISSN 0046-5070
Electronic ISSN 1365-2427
Publisher Wiley
Peer Reviewed Peer Reviewed
Keywords Acoustic telemetry; Barriers; Individual variation; Migration; Rivers
Public URL


Accepted manuscript (1.2 Mb)

Copyright Statement
©2022 University of Hull

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