Grey seals (Halichoerus grypus) as bioprobes: Fine-scale measurements of oceanographic properties using an instrumented large marine predator

Obtaining high resolution data on the physical and biological conditions in marine ecosystems is needed to better understand the impacts of environmental variability. The instrumentation of deep-diving, large marine predators has proven useful in sampling these conditions below the surface at fine spatio-temporal scales that would otherwise be extremely challenging. Data were retrieved from 94 grey seals (Halichoerus grypus; 25 males, 69 females) instrumented with Mk10-AF FastlocTM GPS devices on Sable Island, Nova Scotia, Canada between 2009 and 2015. These devices were programmed to record high resolution location data every 15 min as well as depth (m), temperature (degrees C), and light level every 10 s during dives. Oceanographic data from 595,866 dive profiles were used to estimate mixed layer depth, sea-surface temperature, upper-water column temperature, and chlorophyll-a concentration. Sampling covered about 70% of the Scotian Shelf, with a monthly average of about 26%. These data allow for monitoring of areas that are ecologically important and serve to complement other methods of oceanographic sampling.