Environmental monitoring is required for permitting, consenting, and responsibly developing the marine hydrokinetic (MHK) industry. One method of detecting cumulative effects of MHK devices on fishes is long-term observation of fish abundance at a tidal energy site using discrete hydroacoustic surveys. However, fish abundance in such dynamic environments is highly variable, and survey timing can greatly affect observed trends. We present an approach using survey timing to limit the effects of natural environmental variation on observed long-term trends in fish abundance. We examined three months of a long-term, continuous hydroacoustic dataset from a tidal energy site in Cobscook Bay, Maine, USA. Temporal analyses using Fourier and wavelet transforms indicated non-stationary, cyclic components in fish abundance related to tidal, diel, and semi-lunar cycles. Changes in these patterns over time were likely related to changes in the local fish assemblage. Four discrete sampling schemes were then simulated by sub-sampling the continuous time series: 1- and 24- hour surveys, first randomly spaced over time and then timed to hold tidal, diel, and lunar stages constant. The best discrete sampling design consisted of 24-hour surveys that held lunar stage constant. This design is likely to be effective at similar tidal sites worldwide.
Using Temporal Analysis Techniques to Optimize Hydroacoustic Surveys of Fish at MHK Devices
Title: Using Temporal Analysis Techniques to Optimize Hydroacoustic Surveys of Fish at MHK Devices
September 07, 2015
Conference Name: 11th European Wave and Tidal Energy Conference
Conference Location: Nantes, France
Viehman, H.; Zydlewski, G. (2015). Using Temporal Analysis Techniques to Optimize Hydroacoustic Surveys of Fish at MHK Devices. Paper Presented at the 11th European Wave and Tidal Energy Conference, Nantes, France.