Understanding the impacts of exploitation and fragmentation on the upstream migrating, adult river lamprey (Lampetra fluviatilis [L.]): implications for conservation

Jubb, William M.

Abstract

Globally, freshwater ecosystems are heavily impacted by anthropogenic pressures, including fragmentation and exploitation. Consequently, many negative impacts are observed on numerous fish populations, especially anadromous species.
Currently, there is a dearth of knowledge of river lamprey migration in the Humber catchment, one of the UKs largest river lamprey populations and home to the main English lamprey fishery. Consequently, this study aimed to improve our understanding of the impact of fragmentation and exploitation on the upstream spawning migration of river lamprey in the Humber catchment by carrying out fish tracking studies across three consecutive years (2018/19 to 2020/21) in the two main tributaries to the Humber Estuary: Yorkshire Ouse (2018/19 and 2019/20) and Trent (2020/21).
Lamprey migration throughout the Humber catchment was severely inhibited by barriers to migration, specifically Naburn and Linton-on-Ouse weirs on the Yorkshire Ouse and Cromwell Weir on the River Trent. These structures significantly impacted lamprey distribution throughout the catchment and reduced the numbers reaching spawning habitat upstream. Despite this, Humber lamprey populations were abundant although the vast majority runs up the Yorkshire Ouse compared to the Trent. Nevertheless, lamprey catches in the Ouse were shown to be more complex than lamprey movements throughout the exploited reach, Naburn Weir passage and vulnerability to capture.
Overall, passage remediation is vital to facilitate improved lamprey migration in the Humber catchment, and consequently increase the number of individuals reaching potential spawning habitat whilst management decisions must also account for variability by managing the fishery according to temporal/environmental fluctuations and their potential impact on lamprey behaviour, allowing flexibility in trapping dates and location to ensure sustainability. Nevertheless, the Trent population estimate should be excluded from the current Humber quota with no consumptive take allowed until Cromwell Weir passage is remediated and populations are shown to increase and stabilise relative to the Ouse.

Citation

Jubb, W. M. (2022). Understanding the impacts of exploitation and fragmentation on the upstream migrating, adult river lamprey (Lampetra fluviatilis [L.]): implications for conservation. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4186773

• Thesis Type: Thesis
• Deposit Date: Jan 23, 2023
• Publicly Available Date: Jan 23, 2023
• Public URL: https://hull-repository.worktribe.com/output/4186773
• Award Date: 2022-08