Center of Expertise in Marine Mammalogy

Scientific Research Report
2015-2017

Table of Contents

• Complete Text
• Introduction
• Using aerial infrared images to count ringed seals on ice
• The use of unmanned aerial vehicles (UAV)
• 2017: A Marine Mammal Odyssey, Eh!
• Mark-recapture analysis from long-term study on Sable Island identifies changes in demographic rates in northwest Atlantic Grey Seals
• OTN – Using grey seals (Halichoerus grypus) as bioprobes to estimate phytoplankton biomass
• Northwest Atlantic International Sightings Survey (NAISS) of Marine Megafauna on the Continental Shelf From Northern Labrador to the Bay of Fundy
• Monitoring Movements of Whelping Seals on Drifting Pack Ice
• Marine Mammal Genomics Research in the Central and Arctic Region
• OTN and predator-prey interactions
• Listening in on the Deep: Passive Acoustic Monitoring of Whales off Nova Scotia
• Sharing Meals Keeps Killer Whale Families Together: Provisioning relatives maintains long-term social bonds and helps pass on shared genes
• New developments in the use of fatty acids to determine marine mammal diets
• More than a mouthful – unlocking bowhead whale foraging and reproductive histories from baleen
• Observing walrus behaviour at haulout sites in quasi real-time
• Moving towards automated counting
• References

OTN – Using grey seals (Halichoerus grypus) as bioprobes to estimate phytoplankton biomass

Don Bowen, Fisheries and Oceans Canada
Benia Nowak, Dalhousie University
Damian Lidgard, Dalhousie University
Sara Iverson, Dalhousie University

Although electronic dataloggers and telemetry tags are now routinely placed on marine mammals to study their behavior at sea, more recently these tags are also being used to sample oceanographic features (e.g., temperature, salinity). In this context, marine mammals are referred to as bioprobes – animals used to sample properties of their environment, namely the ocean. An element of the Ocean Tracking Network (OTN) sought to use grey seals as bioprobes to sample ocean temperature and light levels, which together offered a way to estimate the spatial and temporal distribution of phytoplankton abundance. By validating the use of light attenuation as a proxy for phytoplankton biomass in a continental shelf ecosystem, electronic tags can be deployed on wider range of species and allow us to collect fine-scale primary productivity data in other ecosystems. In determining the relative distribution of primary productivity within an ecosystem concurrently with the foraging paths of large marine predators, we may also be able to provide insight on importance of bottom-up drivers for ecosystem structuring.

Grey seals are a wide-ranging species that dive to the ocean floor. Between 2009 and 2016, we fitted 104 adult grey seals with global positioning system (GPS) tags which recorded the surface location about every 15 min, and recorded ocean temperature and light level every 10 sec, during each seal dive. From these data, we could determine the path of the seal and accurately position the recorded temperature and light level during each dive (Fig. 2). Light level attenuates with depth, and more so in the presence of phytoplankton. We calibrated the light level data from seal tags against oceanographic instruments during a series of experiments in the Bedford Basin. These experiments spanned a range of phytoplankton abundances and showed that the seal tags performed well against the oceanographic instruments (Figs. 3 and 4). To estimate phytoplankton abundance along the seal tracks, the ascent portion of each dive from the thermocline to the surface will be used to estimates the downwelling irradiance (light-level attenuation). Downwelling irradiance is then related to chlorophyll-a concentration and coloured dissolved organic matter concentration to provide a relationship that can be used to estimate phytoplankton abundance. In addition to linking seal movement behaviour to environmental conditions (Fig. 5), estimated chlorophyll-a concentrations derived from the seal bioprobes can be compared to ocean colour near- surface measurements from satellite and integrated into models of ocean primary productivity.