Assessment of salmon spawning gravel in the River Frome, Gloucestershire

• Main Author: Mitchell, L
• Format: Report
• Language: English
• Published: UCL Environmental Change Research Centre 2013
• Subjects: Salmo salar
• Online Access: https://discovery.ucl.ac.uk/id/eprint/10114770/1/ecrc_report_157_Mitchell_salmon%20spawning.pdf; https://discovery.ucl.ac.uk/id/eprint/10114770/

Three gravel freeze cores were extracted from each of three sites, identified as potentially suitable for salmon (Salmo salar, L.) spawning, on the River Frome. A quantitative assessment of the capacity of these gravel beds to support effective spawning was made based on the composition of the sampled substrata. Examined sediment size ranges included: optimum spawning gravel (16 > D > 64 mm), fine sediment (D <1 mm ), coarse sand (2 mm > D ≥ 1 mm) and clay (D < 4 µm). A threshold limit of 14% of sediment D <1 mm was used. Results indicated that optimum spawning gravel occurred at all sites in varying amounts. The distribution of these, however, were within the smaller size range suitable for spawning. Moreover, significant deposits of sediment D <1 mm limit potential spawning quality at all sites. The overall composition of substrata at Button Mill offers the best potential spawning habitat of the identified sites.