In-situ ecological interactions with a deployed tidal energy device; an observational pilot study

• Fish abundance surrounding a deployed tidal energy device was assessed.
• Video and ADCP methods were used across different temporal scales.
• Fish were observed aggregating around the device temporarily.
• Abundance declined as tidal velocity rate increased.

At present, few studies exist that consider the relationship between species interactions and key environmental variables, with the added influence of offshore marine renewable energy technologies. Video footage and ADCP survey techniques were used, to examine the presence of fish and velocity flow rates within the vicinity of a deployed tidal energy device. Pilot trials were conducted across 15 day temporal periods, during the summer months of 2009 and 2010. Five random photographic stills were taken from the video footage at hourly intervals throughout each trial day to estimate species presence and abundance. Mean abundance then was compared between hour and day temporal scales and their relationship with velocity rate, for both years.Pollack, Pollachius pollachius was observed aggregating in shoals temporarily round the deployed device, with larger abundance observed in 2009 than 2010. No other species were identified from the surveys. Pollack abundance was significantly associated to velocity rate for both trial years. Increased abundance was related to a reduction in velocity rate for both years, with shoals potentially using the device for temporary protection or feeding strategies. Responses to tidal velocity also differed between years, with 2009 abundances ranging from 0 to 1.2 m/s and 2010 abundances between 0.5 and 1.7 m/s. Overall this preliminary study outlined a potentially useful approach to investigate species responses with new anthropogenic activities in the marine environment.