Description of high-resolution flow velocity and dilution within aquaculture farms in Passamaquoddy Bay, Bay of Fundy, Canada.

Abstract

Water flow through aquaculture farms drives the transport of substances (nutrients, therapeutants and pathogens); however, little is known about the spatial and temporal complexity of water flow at the farm scale. In this study, we quantified flow velocity and dilution at high-resolution (one meter) within Atlantic salmon farms in Passamaquoddy Bay, in the Bay of Fundy. Results suggest that Acoustic Doppler Current Profilers are an effective tool to obtain higher-resolution spatial estimates of water flow to describe particle movement within aquaculture farms. We observed considerable variation in water speed and direction between farms and tidal stages. Variation in the dilution of tracer (milk) was also detected between farms and sampling days and overall milk was diluted to 19 percent of initial concentration in 2.5 minutes (15 meters). Results suggest that farms need to be viewed as unique environments, and illustrate the need to consider the variability of current speed, direction and dilution effect within aquaculture farms.