SEA LAMPREY SPAWNING ASSESSMENT (2015)

Client: Natural England

Best practice conservation monitoring of sea lamprey (Petromyzon marinus) populations currently focuses on the cryptic, relatively sedentary and extended (~5-6 years) life stage of the ammocoetes (larvae); however, survey results and data interpretation remain sensitive to the confidence associated with preferred microhabitat utilisation. With recent research indicating a preference for deep water (>2m), this calls into question the efficacy of existing survey methods, which were designed for water depths <50cm.

Following a pilot study in 2014 which focused  on nest counts to assess population size, characterise habitat preference and study spawning behaviour on the River Frome in Dorset, BUG was commissioned by Natural England to collect a baseline of spatial spawning activity of sea lamprey on the River Teme. The outputs of the survey demonstrated that nest counts provided a rapid and cost effective way to monitor inter-annual trends in adult abundance and assess spatial activity in response to migratory blockages, such as weirs.

The output of the research on the River Frome has now been published and is available online at the following link: Rapid visual assessment of spawning activity and associated habitat utilisation of sea lamprey (Petromyzon marinus Linnaeus, 1758) in a chalk stream: implications for conservation monitoring.

Video footage showing the fascinating spawning behaviour of these fish has also been recorded and is shown below:

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