Describing and Comparing Variability of Fish and Macrozooplankton Density at Marine Hydrokinetic Energy Sites

Abstract

Marine hydrokinetic (MHK) operating licenses require biological monitoring to quantify effects of devices on aquatic organisms, but regulations for instrumentation, measurements, and sampling effort have not been standardized. Assuming stationary acoustic surveys are more cost effective than repeated mobile surveys, the abilities of stationary echosounders, ADCPs, and acoustic cameras to characterize fish densities were compared at a MHK site in Admiralty Inlet, WA. The calibrated echosounder was most sensitive to density changes from vertical migrations, and state-space models confirmed measurements were robust to other variance sources including tidal currents. Peak density variance occurred at a 24-hour period, with cyclic fluctuations in phase with tidal currents and tidal ranges. Six methods used mobile acoustic data to estimate representative spatial ranges of stationary acoustic measurements, resulting in values from 31 to 1,388 m. Design objectives were used to develop a generic framework for the design of distributed monitoring networks at MHK sites.