A Dredging Dilemma: Screening risk to herring and sandeel
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
M. Kyle-Henney, I. Reach, N. Barr, I. Warner, S. Lowe, and D. Lloyd Jones
Abstract
Atlantic herring Clupea harengus and sandeel spp. Ammodytidae are key species of conservation importance inhabiting offshore environments. They are prey species for seabird and marine mammals. Both, herring and sandeel have a preference on seabed substrates for spawning and feeding. To minimize, any adverse environmental effects of dredging operations, regulators have imposed seasonal restrictions upon aggregate extraction activities, resulting on impacts to Atlantic herring spawning substrates (gravels), and seasonal restrictions on reverse screening of coarse substrates upon activities impacting sandeel supporting substrates (sands). In 2013, MarineSpace Ltd was commissioned to produce methods for defining potential spawning habitat for Atlantic herring and potential supporting habitat for sandeel species, for use in Environmental Impact Assessments. This paper describes an evolution of the original method, including a new data layer scoring system to prevent a relative reduction in confidence for existing high-confidence data layers, caused by the addition of new data-layers. The addition of new datasets and the alteration of the scoring system improves the resolution of potential spawning habitats at a regional scale, and a population scale for Atlantic herring and sandeel in the North Sea has been incorporated for the first time. The updated scoring system also promotes professional judgement when determining the suitability of an area as potential spawning or supporting habitat, directly supported by the current UK regulatory advice. Particle Size Analysis is recommended as ground-truthing method to minimise environmental effects and ensure compliance with licence conditions, and can be incorporated into the methodology at a project scale. It is important to highlight the benefits of the improved method with a robust and future-proofed approach to defining potential spawning or supporting habitats. The methodology is intended for use in all UK MAREA regions, but has scope for external use if sufficient data is available.
Keywords: Mapping, ecology, method, future-proof