Abstract
Global interest in mitigating climate change effects is a driver for the development of renewable energy sources. In-stream tidal power, a type of marine hydrokinetic (MHK) energy uses tidal currents to generate electricity and is one example of developing a renewable energy industry. Effects and impacts on fishes in areas of tidal power development are a consideration, and presently there are many unanswered questions in this field of research. Knowledge of how fish use these areas before and after device installation is essential to informing regulators for decision-making. We attempted a Before-After-Control-Impact (BACI) study design to compare an index of fish density near and away from an MHK tidal energy device deployed in Cobscook Bay, Maine. The index was mean volume backscattering strength (Sv) obtained from 24-hour stationary, down-looking hydroacoustic surveys. Data were collected several times per year at an “impact” site within 50–75 m of a device and at a “control” site approximately 1.6 km away, both before and after turbine installation in August 2012. Fish density was lowest in March surveys and highest in May surveys at both sites. One of four comparisons (August 2011/before vs. 2012/after) indicated an interaction of fish density with turbine installation. Operational status of the installed turbine and on-water activity disturbances (e.g., industry vessel and diving activities) varied at the impact site and possibly influenced results. Lower fish densities were observed during installation and maintenance periods than during normal device operation. The effects of construction activities must be separated from the effects of a deployed device to effectively implement a statistically rigorous assessment that could separate the effects of these different activities. This parsimonious approach and results were used for permit licensing by federal and state regulatory bodies at this site and others and can be used to consider regulatory adjustments during different phases of device operation and maintenance.
Highlights
Development and deployment of marine hydrokinetic (MHK) tidal energy devices represent a concerted effort to mitigate environmental concerns of climate change via the development of a new sector of low-carbon-emission renewable energy
This paper presents research designed to assess mid-field effects of the installation, operation, and maintenance of an MHK device in Cobscook Bay, Maine, USA on the fish [22] in the region
Median fish density at the impact site was higher than the control site when only the bottom support frame (BSF) was present without the device in May 2012
Summary
Development and deployment of marine hydrokinetic (MHK) tidal energy devices represent a concerted effort to mitigate environmental concerns of climate change via the development of a new sector of low-carbon-emission renewable energy. Realization of expected positive effects of this development will require technological research to advance from pilot experiments to commercial installations and in-water testing [4,5]. Such testing requires permission from regulatory institutions. The permitting process requires monitoring effects of MHK devices on the environment and adaptive management of that monitoring [6], in the early stages of such new technology. Adaptive management proceeds best when used to guide decision-making, as technologies move through different stages of development [7]
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