Quantifying pursuit‐diving seabirds’ associations with fine‐scale physical features in tidal stream environments

Abstract

Summary1. The rapid increase in the number of tidal stream turbine arrays will create novel and unprecedented levels of anthropogenic activity within habitats characterized by horizontal current speeds exceeding 2 ms À1. However, the potential impacts on pursuit-diving seabirds exploiting these tidal stream environments remain largely unknown. Identifying similarities between the fine-scale physical features (100s of metres) suitable for array installations, and those associated with foraging pursuit-diving seabirds, could identify which species are most vulnerable to either collisions with moving components, or displacement from these installations. 2. A combination of vessel-based observational surveys, Finite Volume Community Ocean Model outputs and hydroacoustic seabed surveys provided concurrent measures of foraging distributions and physical characteristics at a fine temporal (15 min) and spatial (500 m) resolution across a tidal stream environment suitable for array installations, during both breeding and non-breeding seasons. These data sets were then used to test for associations between foraging pursuit-diving seabirds (Atlantic puffins Fratercula arctica, black guillemots Cepphus grylle, common guillemots Uria aalge, European shags Phalacrocorax aristotelis) and physical features. 3. These species were associated with areas of fast horizontal currents, slow horizontal currents, high turbulence, downward vertical currents and also hard-rough seabeds. The identity and strength of associations differed among species, and also within species between seasons, indicative of interspecific and intraspecific variations in habitat use. However, Atlantic puffins were associated particularly strongly with areas of fast horizontal currents during breeding seasons, and European shags with areas of rough-hard seabeds and downward vertical currents during non-breeding seasons. 4. Synthesis and applications. Atlantic puffins' strong association with fast horizontal current speeds indicates that they are particularly likely to interact with installations during breeding seasons. Any post-installation monitoring and mitigation measures should therefore focus on this species and season. The multi-species associations with high turbulence and downward vertical currents, which often coincide with fast horizontal current speeds, also highlight useful pre-installation mitigation measures via the omission of devices from these areas, reducing the overall likelihood of interactions. Environmental impact assessments (EIA) generally involve once-a-month surveys across 2-year periods. However, the approaches used in this study show that more focussed surveys can greatly benefit management strategies aiming to reduce the likelihood of negative impacts by facilitating the development of targeted mitigation measures. It is therefore recommended that these approaches contribute towards EIA within development sites.

Taking movement data to new depths: Inferring prey availability and patch profitability from seabird foraging behavior

“…Animal behavior and ecology are intricately linked to environmental conditions which are dynamic in space and time (Phillips, Croxall, Silk, & Briggs, ; Shaffer et al., ; Weimerskirch et al., ). Seabirds perform behaviors over multiple spatiotemporal scales (e.g., dives nested within dive bouts), and clear associations are recorded corresponding to biophysical phenomena that lead to patchiness (Cox, Scott, & Camphuysen, ; Pinaud, ; Pinaud, Cherel, & Weimerskirch, ; Waggitt et al., ).…”

Environmental heterogeneity amplifies behavioural response to a temporal cycle

“…There is also evidence that seabird numbers fluctuate with the tide further offshore (Zamon 2003, Embling et al 2012, Cox et al 2013, although the nature of these relationships varies between locations (Zamon 2003, Embling et al 2012, Cox et al 2013. Such geographic differences in behavioural responses to the tidal cycle may arise because of locationspecific interactions between bathymetry and tidal currents (Scott et al 2013, Waggitt et al 2016, Cox et al 2018). The surrounding environment may also play a key role in shaping behavioural responses, and therefore warrants further study (Benjamins et al 2015).…”

Automatic active acoustic target detection in turbulent aquatic environments

“…Deployments of the FLOWBEC‐4D platform (FLOw, Water column and Benthic ECology 4‐D) were performed at the European Marine Energy Centre (EMEC) test sites, UK (Williamson et al ). These deployments gathered multifrequency echosounder data with synchronized multibeam echosounder measurements (Williamson et al ) and were further supported by hydrodynamic model data for the sites (Waggitt et al ). This paper uses datasets collected in a tidal channel during two platform deployments at the full scale tidal test site at the Fall of Warness, UK (59°7′ to 59°11′N, 2°47′ to 2°50′W), at approximately 35 m depth during summer 2013.…”