At the height of the first Covid19 lockdown in the UK, nine experts generously gave their time and expertise to help us improve estimates of the passability of different infrastructures for European eels (Anguilla anguilla). We are pleased to announce that the fruits of their labours have just been published here in Conservation Science and Practice!

Conservation efforts are hampered by limited understanding about how different types of instream infrastructure impact migration patterns and fish survival. To address this knowledge gap, we used a rapid, fully online IDEA protocol (Hemming et al. 2018) to elicit expert judgements for the passability of seven different in-stream infrastructures to elver European eels (Anguilla anguilla) in Great Britain. Nine experts provided judgements via our online survey, followed by a second elicitation via email for reflection and adjustment of initial estimates.

We found that on average, bridges were judged the most passable (95% passability), followed by fords, non-perched culverts, weirs, sluices, dams and perched culverts (7%). Results showed a high degree of agreement about how passable bridges and perched culverts are for elver eels, but less certainty about other infrastructure. In qualitative data also gathered via the survey, we identified 34 distinct factors that experts believed influence infrastructure passability for elver eels, including: the structure itself, hydraulics, elver characteristics, obstructions (e.g., debris accumulation), and vegetation (e.g., to aid climbing).

In the paper, we discuss how our rapid, online-only variation on the IDEA protocol compares with the more traditional protocol, and how the expert estimates generated in this study can be used in future scenario building and connectivity modelling, with a view to improving conservation to support species persistence.

We hope you enjoy the paper, and we would like to take this opportunity to thank the participants in this study, without whom it would not have been possible. Thank you!

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