Moored floating structures associated with offshore wind turbines will expand significantly in scope and extent, including increasing depths and distances from shore. Floating windfarms are therefore increasingly likely to be deployed within highly productive shelf areas, important for many wide-ranging migratory species including demersal and pelagic fish and their predators (marine mammals, seabirds, elasmobranchs). Ecological significance of such structures, in terms of influence on mobile species, remains poorly understood but could be substantial based on current knowledge about the ability of existing static offshore structures (e.g., oil & gas platforms) to attract and retain fish communities. Attraction of fish to floating objects in (sub-)tropical waters is well known and widely exploited through use of Fish Attracting Devices (FADs). However, much less is known about comparable effects of floating structures at higher latitudes.
If persistent fish aggregations develop around floating offshore windfarms or similar infrastructure, this could influence the distribution of other predators such as marine mammals, seabirds and elasmobranchs, with unknown conservation consequences including effects of renewables on foraging behaviour and changes to prey distribution, and thus potential for population-level impacts. This project seeks to develop understanding of spatiotemporal distribution of fish in shelf seas in response to moored floating offshore structures and investigate whether such structures represent attractive foraging locations for top predators (vocalising cetaceans).
The IFLOW project will design and undertake measurement of fish distribution, biomass, and cetacean presence at representative Scottish continental shelf locations. Data will be collected using an instrumented seabed lander in habitats suitable for floating offshore wind development across temporal scales of weeks to months. Active acoustics (echosounder/ADCP) will be combined with passive acoustic monitoring allowing investigation of longer-term spatiotemporal variability of fish and cetacean distributions in the absence of floating structures, in relation to various environmental covariates (e.g., tidal variables, fronts, net primary productivity, surface temperature, chl-a; derived from this study, remote sensing, or NERC NEODAAS), and present a baseline against which future studies can be compared.
Using the same landers, the project will collect fish distribution data at representative floating structures. The project will compare observations from structures and reference sites to quantify changes in fish distribution, monitor temporal trends, and assess potential FAD effects, considering structure ages and biofouling levels. Concurrent passive acoustic monitoring will allow assessment of the effects of potential fish aggregation among floating structures on cetaceans. A metanalysis will be performed between results obtained in this study and those reported for fixed offshore structures (e.g., fixed-bottom wind turbines, hydrocarbon platforms) to assess specific effects of floating structures. In this way, attractiveness to fish, and thereby to marine top predators, of floating structures in shelf-sea environments can be evaluated. These results will allow for improved assessment of cumulative impacts of expanding floating offshore wind and other infrastructure in offshore shelf environments via publication and industry/policy engagement.
For more details please contact:
Benjamin Williamson (ERI) https://eri.ac.uk/members/benjamin-williamson/