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Agent-based modelling of juvenile eel migration via selective tidal stream transport

Benson, Thomas; de Bie, Jasper; Gaskell, Jennifer; Vezza, Paolo; Kerr, James R.; Lumbroso, Darren; Owen, Markus R.; Kemp, Paul S.

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Authors

Thomas Benson

Jasper de Bie

Jennifer Gaskell

Paolo Vezza

James R. Kerr

Darren Lumbroso

Paul S. Kemp



Abstract

Recruitment of temperate eel species Anguilla anguilla, A. rostrata & A. japonica has declined over the last few decades due to human activities, such as overfishing and construction of migratory barriers (e.g. dams, weirs and sluices) and hazardous energy infrastructure (e.g. turbines, intakes and outfalls). Numerical models, substantiated with data from field and laboratory studies, can potentially predict and quantify the relative impacts of such activities, thereby assisting in the sustainable management of eel populations. Here, we present an agent-based model (ABM) of juvenile eel migration up estuaries. The model includes relevant eel behaviours and environmental conditions that, according to the literature, influence upstream migration. Crucially, by assessing the local salinity gradient and relative flow direction, the modelled eels (agents) self-determine whether the tide is flooding or ebbing and orientate themselves for navigation, with no top-down instructions. This allows the agents to decide which particular behaviour to undertake as part of Selective Tidal Stream Transport (STST). The developed ABM is coupled to a hydrodynamic model of the Thames Estuary and the results substantiated by comparison against eel trap data. Combinations of the various STST behaviours are systematically tested and the influence they have on up-estuary migration is assessed in terms of relative energy expenditure. The parameterised model is then used predictively at Milford Haven Waterway to investigate potential impacts on the juvenile eel population due to entrainment in a power plant cooling water intake and outfall. Results from the Thames model case study indicate that including bed anchoring behaviour is essential for achieving a good comparison with the eel trap data and the choice of salinity detection threshold is also important. If daylight avoidance (diel) behaviour is not included, the most energy efficient migration is achieved using just two STST behaviours (ebb tide bed anchoring and upward migration during flood). With diel behaviour included, energy expenditure is greater, but some efficiency is regained by including all of the STST behaviours. For the Milford Haven case study, the model predicted a juvenile eel intake and outfall entrainment rate of 2.0% and 4.7%, respectively. It is concluded that the ABM is a valuable tool for assessing potential impacts on the recruitment of eels (extendable to other species) and could be used to assist in site-selection and low impact design of energy infrastructure in tidal environments.

Citation

Benson, T., de Bie, J., Gaskell, J., Vezza, P., Kerr, J. R., Lumbroso, D., …Kemp, P. S. (2021). Agent-based modelling of juvenile eel migration via selective tidal stream transport. Ecological Modelling, 443, Article 109448. https://doi.org/10.1016/j.ecolmodel.2021.109448

Journal Article Type Article
Acceptance Date Jan 10, 2021
Online Publication Date Jan 21, 2021
Publication Date Mar 1, 2021
Deposit Date Jan 22, 2021
Publicly Available Date Mar 29, 2024
Journal Ecological Modelling
Print ISSN 0304-3800
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 443
Article Number 109448
DOI https://doi.org/10.1016/j.ecolmodel.2021.109448
Keywords ABM, Agent-based model, Glass eel, Elver, IBM, Migration, Selective tidal stream transport.
Public URL https://nottingham-repository.worktribe.com/output/5250527
Publisher URL https://www.sciencedirect.com/science/article/pii/S0304380021000211
Additional Information The work was done at the Centre for Mathematical Medicine and Biology.

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