1. Introduction

  1. This Fish and Shellfish Ecology Technical Report provides a detailed baseline characterisation of the fish and shellfish ecology (e.g. species, communities and habitats) of the Array. The Array refers to the offshore components of Ossian, including infrastructure such as wind turbines, offshore substation platforms and inter-array/interconnector cabling. The offshore area in which the Array will be located is referred to as the ‘site boundary’. This baseline characterisation has been informed using site-specific survey data, data from third-party organisations, and the most recent desktop data and published literature available for fish and shellfish within the northern North Sea, where the site boundary is located.
  2. The aim of the technical report is to provide a robust baseline characterisation of the fish and shellfish resources within a defined study area (refer to section 2) against which the potential impacts associated with the Array can be assessed. To support the impact assessment in the Environmental Impact Assessment (EIA) Report, the ecological information presented in this technical report has been used to identify a number of Important Ecological Features (IEFs). IEFs have been determined based on the conservation, ecological and commercial importance of each identified feature within the site boundary and within the fish and shellfish ecology study area, in line with published Ecological Impact Assessment guidelines (Chartered Institute of Ecology and Environmental Management (CIEEM), 2022) (refer to section 5.2).

2. Study Area

  1. As fish and shellfish are spatially and temporally variable, a broad fish and shellfish ecology study area has been defined for the purposes of baseline characterisation.
  2. The fish and shellfish ecology study area proposed is reduced compared to the fish and shellfish ecology study area presented in the Array EIA Scoping Report (volume 3, appendix 6.1). Consultation feedback received from Marine Directorate - Licensing Operations Team (MD-LOT, 2023) advised that though they were “broadly content with the proposed fish and shellfish ecology study area” presented in the Array EIA Scoping Report (hereafter referred to as 'Scoping Report'), “identifying a smaller study area using the recommended methods detailed in the NatureScot representation” was recommended. NatureScot advised in their Scoping Report response in relation to the fish and shellfish study area that they “advise that this is a very large area. The Applicant may wish to consider a smaller study area based on either International Council for the Exploration of the Sea (ICES) rectangles or modelled subsea noise and/or suspended sediment concentrations (SSCs) data, whichever extend furthest from the site” (MD-LOT, 2023). Therefore, the revised fish and shellfish ecology study area is based on a precautionary zone of influence of subsea noise (100 km), including the Firth of Forth, and is presented in Figure 2.1   Open ▸ .
  3. The fish and shellfish ecology study area provides a wide context for the spatially and temporally variable species and populations, including diadromous fish, which are known to occur within and in the vicinity of the site boundary. This fish and shellfish ecology study area will ensure the characterisation of all fish and shellfish receptors within the area and is therefore large enough to consider all direct (e.g. habitat loss/disturbance within the site boundary) and indirect impacts (e.g. underwater noise over a wider area) associated with the Array on identified receptors.

Figure 2.1:
Fish and Shellfish Ecology Study Area

Figure 2.1: Fish and Shellfish Ecology Study Area


3. Baseline Methodology

3.1. Methodology

  1. A desktop review has been undertaken to inform the baseline for fish and shellfish ecology, including review of a number of peer-reviewed publications and reports from surveys undertaken to inform other project assessments. These provide information on the fish and shellfish assemblages within the fish and shellfish ecology study area. In addition, the benthic subtidal ecology site-specific survey undertaken within the site boundary in July 2022 has also been used to inform the baseline characterisation for fish and shellfish ecology. This survey is described in section 3.3.
  2. The fish and shellfish ecology baseline has also been informed by the commercial fisheries baseline characterisation (volume 3, appendix 12.1) and the benthic subtidal ecology baseline characterisation (volume 3, appendix 8.1) in addition to consultation with relevant bodies.

3.2. Desktop Study

  1. A detailed desktop review of existing studies and datasets was undertaken to gather information on fish and shellfish ecology within the fish and shellfish ecology study area. Table 3.1   Open ▸ summarises the studies and datasets used.

 

Table 3.1:
Summary of Key Desktop Studies

Table 3.1: Summary of Key Desktop Studies

 

3.3. Site-Specific Surveys

3.3.1. Array

  1. Considering the studies and datasets available covering the site boundary and the wider northern North Sea, to characterise the baseline for fish and shellfish ecology no site-specific fish and shellfish ecology surveys have been carried out to inform the impact assessment for fish and shellfish specifically. However, Table 3.2   Open ▸ provides a summary of the 2022 site-specific benthic subtidal ecology survey, which has been used to inform the fish and shellfish ecology baseline characterisation. The sampling locations from the 2022 site-specific survey are presented in Figure 3.1   Open ▸ . Survey operations were conducted aboard the Motor Vessel (M/V) Northern Maria by Ocean Infinity; further information is available in volume 3, appendix 8.1, annex A.
  2. The benthic subtidal ecology site-specific survey included combined grab and Drop Down Video (DDV) sampling at 80 sampling stations ( Figure 3.1   Open ▸ ), all within the site boundary (refer to volume 3, appendix 8.1). Samples from two stations were excluded from Particle Size Analysis (PSA) analysis, due to incomplete grab closure at S008 (meaning sample loss occurred), and a small sample recovered at S025 which was below the minimum acceptance criteria, despite multiple attempts to acquire an acceptable volume. Ten of the 80 grab stations were also sampled for sediment contaminants; full details are provided in volume 3, appendix 8.1. Site-specific epibenthic beam trawl sampling was conducted at ten of the 80 environmental stations across the site boundary ( Figure 3.1   Open ▸ ) to support characterising the epifaunal component of the benthos within the site boundary. The PSA and other sample data and observations have been used to support characterisation of the fish and shellfish ecology baseline, with the PSA data specifically informing the substrate suitability assessments for both herring Clupea harengus spawning and sandeel Ammodytidae spp. habitation. The results are presented in sections 4.1.2, 4.4.2 and 4.5.2.
  3. The habitat suitability for herring and sandeel was characterised using PSA results from site-specific grab sampling and seabed imagery (supported by geophysical datasets) across the site boundary which characterised the seabed types and sediment composition (refer to volume 3, appendix 8.1). Further, species presence/absence records were also recorded from both grab samples and DDV sampling, although these should be noted as purely opportunistic and incidental data as surveys were not specifically designed to target fish and shellfish species.
  4. For herring spawning habitat characterisation, samples were classified into preferred, marginal and unsuitable based on their suitability as spawning habitat using classifications from Reach et al. (2013). These classifications assigned each grab sample with a herring spawning suitability category based on the relative proportions of fines, sands and gravel. Additional data from the IHLS showing herring spawning intensity have been used, in line with the guidelines set out by Boyle and New (2018), to complement the characterisation of spawning habitats and activity for herring in the fish and shellfish ecology study area. The abundance of larvae ≤10 mm per m2 were plotted as heat maps for the years 2007 to 2016. These maps, combined with the PSA data from site specific grab sampling, were used to determine where key spawning habitats were located in the vicinity of the site boundary (refer to section 4.4, Figure 4.7   Open ▸ to Figure 4.12   Open ▸ ).
  5. For sandeel habitat characterisation, a similar approach to herring was used to classify habitats into preferred, marginal and unsuitable categories within the site boundary based upon habitat suitability classifications derived from Latto et al. (2013). As for herring, these classifications are based on the proportions of fines, sand and gravel in the grab samples. Incidental sandeel observations were also collated from the site-specific benthic grab samples (refer to section 4.5, Figure 4.14   Open ▸ and Figure 4.15   Open ▸ ). Furthermore, the predicted distribution model for sandeels in the North Sea published by Langton et al. (2021) has been mapped in relation to the site boundary in order to determine areas where the probabilities of sandeel presence and density are high (refer to section 4.5, Figure 4.13   Open ▸ ).
  6. Norway lobster Nephrops norvegicus (referred to as Nephrops hereafter) presence within the site boundary was assessed through abundance data collected from epibenthic trawls, as well presence/absence of individuals and/or burrows derived from DDV sampling (refer to section 4.8.6 for results).

 

Table 3.2:
Summary of Site-Specific Surveys Undertaken to Inform Fish and Shellfish Ecology Baseline Characterisation

Table 3.2: Summary of Site-Specific Surveys Undertaken to Inform Fish and Shellfish Ecology Baseline Characterisation

Figure 3.1:
Site-specific Surveys Locations

Figure 3.1: Site-specific Surveys Locations

3.3.2. Fish and Shellfish Ecology Study Area

  1. The results from site-specific surveys undertaken for other recent projects in the vicinity of the site boundary have also been used to inform the baseline characterisation for fish and shellfish assemblages within the fish and shellfish ecology study area. The methods engaged are summarised below and further detail is provided within the baseline characterisation in section 4 where appropriate.
  2. Epibenthic beam trawl surveys were conducted in August 2020 across 15 locations within the proposed Berwick Bank Offshore Wind Farm, located 56.77 km to the south-west of the site boundary ( Figure 3.2   Open ▸ ) (SSER, 2022). In 2012, four otter trawl surveys were conducted across the Development Area for Inch Cape Offshore Wind Farm (86.90 km south-west of the site boundary) (Inch Cape Offshore Limited, 2018). In 2011, a total of 53 epibenthic trawls were conducted within the Seagreen Alpha and Seagreen Bravo Offshore Wind Farms (now referred to as Seagreen 1 Offshore Wind Farm and Seagreen 1A Project) (located 50.72 km to the south-west of the site boundary) (Seagreen Wind Energy, 2012). In 2009, a site-specific benthic survey was conducted for Neart na Gaoithe Offshore Wind Farm (located 105 km south-west of the site boundary). This benthic survey also recorded fish species within the Neart na Gaoithe study area (Mainstream Renewable Power, 2019).
  3. These site-specific surveys provide useful information on the general seabed types, sediment suitability for fish spawning (specifically sandeel and herring) and/or habitat for benthic fish and shellfish species. These site-specific surveys also provide opportunistic records of small demersal fish and shellfish species present within the fish and shellfish ecology study area.
  1. Site-specific data collected as part of Digital Aerial Surveys (DAS) for marine mammals and birds conducted monthly between March 2021 and February 2023 have the potential to record basking shark Cetorhinus maximus within and in the vicinity of the site boundary, however none were recorded during the survey programme therefore no data will be included within this baseline characterisation (refer to volume 3, appendix 8.1).

Figure 3.2:
Location of Offshore Wind Developments with Site-Specific Data used to Characterise the Fish and Shellfish Ecology Baseline

Figure 3.2: Location of Offshore Wind Developments with Site-Specific Data used to Characterise the Fish and Shellfish Ecology Baseline