Abstract
Measuring spatial and temporal variation in diving animals (seabirds and marine mammals) occupancy of tidal stream energy development sites help assess how populations could interact with installations (Waggitt and Scott 2014). This information is conventionally provided with boat-based surveys. To measure spatial and temporal variation in diving animals use of the Morlais Demonstration Zone (MDZ) in northwest Anglesey, 2 complementary boat-based surveys (observations and hydrophones) have been performed per calendar month since May 2022. Spatial variations of relevance are differences in animal densities (individuals per km2) within and outwith the MDZ; temporal variations of relevance are differences in animal densities amongst months. By measuring variation in animals densities before installations, boat-based surveys can contribute to several Environmental Monitoring and Mitigation Plans (EMMP) indicators: (I1) Change in use of tidal device array deployment area pre and post installation, (I2) Changes in use of the wider MDZ outside the array deployment area, (I4) Avoidance of array of tidal devices (far field avoidance). Accordingly, these surveys contribute to the following EMMP questions: (Q1) Is there evidence that receptors use the tidal device array deployment areas in the same of similar ways pre and post deployment, (Q2) Is there evidence that receptors use the MDZ in the same or similar ways pre and post deployment, and (Q3) If there evidence of a change to use of the deployment area, is it considered ecologically significant by the advisory group? By providing measurements of animal densities in different scenarios, these surveys can also contribute to: (I9) Validation of Encounter Risk (ERM) and Collision Risk (CRM) models. This interim report will: (1) explain and summarise the survey design, and (2) present data and analyses of monthly surveys between May 2022 and April 2023. A Final Report in May 2024 will: (1) present data and analyses of monthly surveys from May 2022 to April 2024, (2) amalgamate data collected in 2022-2024 with that collected in 2016-2018 (Morlais 2019, Veneruso et al 2019), investigating animals spatial and temporal occupancy of the MDZ across 4 years, (3) present data and analysis from complementary intensive surveys (3 days in < 1wk) and echosounder measurements.