Optimizing Sampling Based on Temporal Variation in Fish Abundance at a Tidal Energy Site in Cobscook Bay, ME

Environmental monitoring is required for permitting and responsibly developing the marine hydrokinetic (MHK) industry.  Hydroacoustics have proven useful for monitoring effects of MHK devices on fishes. However, funds for equipment, boat time, and data processing are always limited.  Efficient sampling is therefore essential, but areas with strong tidal currents are highly variable. Discrete sampling events could result in mistaking natural variation for turbine effects.  Continuous sampling is rarely an option, but discrete samples may be timed to mitigate the influence of natural variation on results.  A side-looking echosounder has been collecting continuous data on fish abundance and behavior (e.g., swim direction and speed) at a tidal site since March 2014. The acoustic beam is oriented to monitor along the face of an MHK turbine that is not currently deployed.  We will use these ‘baseline’ data to characterize temporal variation in fish abundance and behavior.  Methods will be applied to a full year of continuous data (Mar 2014-Mar 2015) as they are collected, and a subset of data will be presented for discussion.  Results will be used to devise an optimal schedule for discrete sampling that maintains the ability to discriminate MHK device effects from natural variation while lowering monitoring costs.