ECOLOGICAL IMPACT ASSESSMENT

14 Marine Scientist No.48 August 2014

Working in the off-shore wind sector over the past few years has been both

interesting and challenging. Be-cause of the novel nature of the industry, the increased scale of developments and the uncertain-ties associated with offshore wind farm construction and operation, the level of information required to undertake Ecological Impact Assessment (EcIA) has increased considerably since the first off-shore wind farms built in the first of the Crown Estate leasing rounds.

One of the key impacts on fish ecology from offshore wind farms is underwater noise as-sociated with construction, par-ticularly piling of foundations for offshore structures (e.g. turbines and substations). In extreme cases, piling noise can lead to injury or mortality to fish, though only in close prox-imity to piling operations and

the use of standard soft start procedures reduces the poten-tial for injury effects.

The two key issues relating to the potential effects of underwa-ter noise on fish are disturbance of spawning habitats and disrup-tion of fish migration to/from spawning habitats. I have worked on these two issues for a number of offshore wind farm projects including Triton Knoll, Hornsea Projects One and Two and Atlan-tic Array.

Fish spawningOne of the most important

factors when undertaking impact assessments on fish spawning habitats is accurate, reliable base-line characterisation data. These can help to define the extents of spawning habitats and the timing of peak spawning for key species. This ensures that impact assess-ments are as accurate as possible while maintaining an appropriate level of precaution.

For assessing impacts on fish spawning, we have used site spe-cific survey data and existing baseline data, including a range of literature and data sources, to refine the broad scale spawn-ing and nursery habitats mapped across the UK (e.g. Coull et al. 1998; Ellis et al. 2012). One of the more sensitive fish species to un-derwater noise is herring (Clupea harengus). This species has specif-ic habitat requirements (eggs are laid on gravelly substrates) and is known to have high site fidelity in their spawning grounds.

Herring is also a prey species for a range of bird and marine mammals and therefore plays a key ecological function, increas-ing the importance of avoiding population level effects on this species. As such, it is important when carrying out impact as-sessments to try to delineate the spawning habitats that are used most frequently. Information from the fishing industry and

Ecological Impact Assessment for Offshore Wind Farms

Dr Kevin Linnane is a Chartered Marine Scientist and Senior Marine Ecologist with RPS, an interna-tional consultancy providing advice and technical services for the offshore renewables industry, the exploration and production of oil, gas and other nat-ural resources and offshore and coastal infrastruc-ture projects. As a specialist in Ecological Impact Assessment for offshore wind farm developments, Kevin has considerable experience in dealing with a range of marine ecological issues, with a particu-lar focus on subtidal benthic habitats and fish and shellfish ecology. Kevin works within the RPS marine ecology team comprising ten marine scientists from a range of backgrounds and covering a variety of technical disciplines.

ECOLOGICAL IMPACT ASSESSMENT

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No.48 August 2014 Marine Scientist 15

an understanding of the sedi-ment composition can be useful in delineating these areas. One of the most reliable indicators of herring spawning habitats is the presence of high abundances of herring larvae and data from the International Herring Larvae Survey (IHLS)1 are often used to delineate these habitats.

Once there is agreement on the location and extents of spawn-ing habitats and the timing of spawning, underwater noise mod-elling is used to estimate the dis-tance at which behavioural effects (i.e. avoidance) may occur during piling operations, with a view to quantifying the magnitude of the effect on spawning fish (i.e. the degree of overlap with spawning habitats, numbers of spawning seasons affected, etc.).

This is a developing field and there are therefore uncertain-

ties associated with these mod-els, with different approaches to modelling and different criteria used to estimate the ranges at which behavioural effects may occur. Additionally, there are un-certainties about the behavioural responses of fish to underwater noise with the level of behav-ioural disturbance dependent on a number of factors, such as the type of fish, its sex, age and condition, as well as other stres-sors to which the fish is or has been exposed. The response of the fish will also probably de-pend on the reasons and drivers for the fish being in the area. For example, spawning may poten-tially increase the desire for the fish to remain in the area despite the elevated noise levels.

Because of these uncertainties, an element of precaution needs to be included in these assessments (e.g. in relation to fish behavioural response to noise), whilst ensur-ing that the assessment is realistic

when also considering the addi-tional precaution inherent in the ‘Rochdale Envelope’ approach (i.e. assessing the maximum ad-verse scenario for the project2).

Fish migrationImpacts on fish migration as

a result of underwater noise from piling operations may also occur. Although many fish species mi-grate in the marine environment (e.g. to feeding or nursery habi-tats), diadromous fish species (fish that migrate between fresh and salt water) are particularly sensitive be-cause their life cycles require them to move between the sea and riv-ers/estuaries at particular times of year. Impacts on these species can be more difficult to predict due to considerable uncertainties associ-ated with the at-sea behaviour and their distribution.

Most of the information avail-able on these species is from rivers and estuaries, with records made while they are migrating to/from spawning habitats. Records of di-adromous fish species further off-shore are sporadic, making it dif-ficult to predict accurately where these species are likely to occur relative to offshore wind farms. As a result of these uncertainties, im-pact assessment on these species has generally focused on the po-tential for underwater noise from piling operations to create barri-ers with the coast during key mi-gration periods. Reliable data on peak migration periods for migra-tory fish species are more readily available than data on at-sea be-haviour or distribution.

Ecological Impact Assessment for Offshore Wind Farms

Dr Kevin Linnane, a specialist in Ecological Impact Assessment for offshore wind farm developments, writes about the exciting challenges of his work

Atlantic white-sided dolphins

Bottlenose dolphin

1 The IHLS is a long-term (1967-present) survey programme coordinated by ICES, with the main objective to provide esti-mates of herring larval abundances in the North Sea and surrounding area, to pro-vide a relative index of changes of the her-ring spawning stock biomass. 2 The ‘Rochdale Envelope’ is an approach to consenting and environmental impact named after two UK planning cases (R. v Rochdale MBC ex parte Milne (No. 1) and R. v Rochdale MBC ex parte Tew [1999] and R. v Rochdale MBC ex parte Milne (No. 2) [2000]). It allows a project description to be broadly defined, within a number of agreed parameters, giving some flexibility while a project is in the early stages of development (i.e. during the consenting process).

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ECOLOGICAL IMPACT ASSESSMENT

16 Marine Scientist No.48 August 2014

Because there are uncertain-ties associated with the behaviour-al responses of fish to underwater noise, and because many migra-tory fish species are also features of Special Areas of Conservation, designated under the EC Habitat Directive, the precautionary prin-ciple must also be applied, i.e. consent cannot be given unless it is ascertained that there will be no adverse effect on the integrity of the site. It is therefore important to ensure assessments are under-taken in a robust manner, based on the best available science, while also ensuring that an adequate level of precaution is assumed within the assessment to comply with the Habitats Directive.

MitigationIn some circumstances, there is

a need for mitigation to reduce im-pacts of underwater noise on ma-rine species (including fish spawn-ing and migratory fish). In the UK, this has taken the form of seasonal restrictions on piling operations, though in Germany noise reduc-tion technologies (e.g. bubble cur-tains) are routinely used to reduce noise levels associated with off-shore wind farm piling operations (though this mitigation is designed for marine mammals). More re-cently, due to the increased size of offshore wind farms and the great-er certainty associated with map-ping fish spawning habitats, it has been possible to manage piling op-erations within offshore wind farm sites to ensure piling, in certain parts of wind farm sites, is either avoided or undertaken at lower hammer energies during certain periods (e.g. during fish spawning or migration).

We continue to work with a number of offshore wind farm developers to reduce impacts on fish by scheduling construction to ensure impacts on fish species are minimised or, where possible, avoided completely. This will in-volve compilation of reliable base-line data on location and timing of spawning/migration and work-ing with engineers to ensure that construction operations (includ-ing piling operations) are spa-

tially and temporally managed to minimise noise disturbance from piling in the vicinity of the most sensitive habitats during the peri-ods of highest sensitivity.

This approach also takes into account more detailed informa-tion on the ground types across the offshore wind farm site (and therefore the hammer energies likely to be required in certain areas) and more detailed project design information (i.e. founda-tion types and locations) that may not have been available at the time of consenting. This provides one practical solution to mitigating the effects of piling-related underwa-ter noise on fish populations, whilst ensuring that construction on large offshore wind farms does not cease, causing significant de-lays to project programmes and cost implications.

ReferencesBexton, S., Thompson, D., Brownlow,

A., Barley, J., Milne, R. and Bidewell, C. (2012) Unusual mortality of pinnipeds in the United Kingdom associated with heli-cal (corkscrew) injuries of anthropogenic origin. Aquatic mammals 38(3): 229–240.

Coull, K.A., Johnstone, R. and Rogers, S.I. (1998) Fishery Sensitivity Maps in British Waters. Published and distributed by UK-OOA Ltd.

Ellis, J.R., Milligan, S.P., Readdy, L., Taylor, N. and Brown, M.J. (2012) Spawning and Nursery Grounds of Selected Fish Spe-cies in UK Waters. Sci. Ser. Tech. Rep., Cefas, Lowestoft, 147: 56 pp.

Harwood, J., King, S., Schick, R., Dono-van, C. and Booth, C. (2014) A Protocol for Implementing the Interim Population Consequences of Disturbance (PCoD) Approach: Quantifying and Assessing the Effects of UK Offshore Renewable Energy Developments on Marine Mam-mal Populations. Report number SMRUL-TCE-2013-014. Scottish Marine and Fresh-water Science, 5(2).

A piling vessel installing an offshore wind turbine foundation

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RPS Marine Mammal Project TeamPotential impacts on marine mammals from offshore development are often a contentious issue. Navigating through various technical reports, legislative frameworks, and possible con-flicts during consultation can present a minefield to the consultant. The RPS marine mammal project team has met these challenges head on and has exponentially increased their capabil-ity in marine mammal ecology and impact assessments through training, hands on experience, and collaboration and networking with scientific institutes.

The team comprises marine mammal ecologists, underwater acousticians, GIS technicians and environmental practitioners. Our project experience has spanned different sectors, includ-ing offshore renewables, oil and gas and ports and harbours. All aspects of marine mammal related capabilities can be covered, including marine mammal and acoustic surveys, data analysis and interpretation, underwater noise modelling, impact assessment, Habitats Regula-tion Assessment reports, European Protected Species risk assessments and licence applica-tions, and mitigation and monitoring design.

In the last year RPS has also formed a Marine Mammal Working Group, led by Dr Tessa McGarry and Tamara Al-Hashimi. Tessa and Tamara have considerable experience in EcIA, and have acted as marine mammal advisors for a number of key offshore wind farm and oil and gas projects. The Working Group, made up of members in the UK, America and Australia, aims to ensure that RPS specialists are up to speed on the most recent developments around the globe with regard to key issues and emerging topics.

To achieve this, members of the Marine Mammal Working Group regularly attend seminars, conferences and workshops on marine mammal related topics and keep abreast of current scientific research in this area. For example, we are following the latest scientific research relat-ing to potential behavioural effects of subsea noise on marine mammals and in particular the forthcoming PCoD (Population Consequences of Disturbance) framework, which will provide a useful tool for assessing population level effects (Harwood et al., 2014). Similarly, we are monitoring the work on corkscrew injury that has arisen out of a nationwide concern that marine mammals (in particular seals) may be vulnerable to injury from collision with vessels that use ducted propellers (Bexton et al., 2012). The Marine Mammal Working Group maintains strong links with academic institutions and technical specialists and often works in collaboration with recognised experts in the field.

Harbour seal

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