North Atlantic seal science

Discover why we research seals and what we study, including population, predation, and the impacts of climate and ecosystem changes.

Our research activities

There are 6 seal species that commonly live in Canadian waters. We have largely focused on studying harp, grey and hooded seals, given that they are commercially harvested. In recent years, ecosystem considerations, such as climate change and predation on fish stocks have further increased the importance of research on these species. We are working on a variety of innovative scientific projects to learn about their:

habitat
ecology
population dynamics
seasonal movements
diet and feeding behaviour

Our research is focused on:

population status
the role of seals in the ecosystem
commercial and subsistence harvest
human impacts on seals and their ecosystems
ecosystem considerations, such as climate change and oceanographic factors

Population

For several decades, we have estimated the size of Atlantic seal populations in order to manage commercial seal harvests and to better understand the role of seals in marine ecosystems.

Harp, grey and hooded seals congregate in breeding colonies, some of which can be large, to give birth to their pups. Since it would be impossible to directly count the total number of seals in the Northwest Atlantic, we estimate the size of a population by counting the number of pups born in these colonies. We do visual aerial surveys and take photos of the pups. We then count the number of pups in the photos to calculate the overall population size and assess population trends using estimates of:

pups born
pregnancy rates
removal levels, such as harvests

By the early 1970s, harvesting drove some Canadian seal populations to an all-time low and the department determined that management measures were needed to maintain these populations at a healthy level. Management measures included harvest seasons and required monitoring. Since implementing these measures, harp and grey seals have recovered close to pre-sealing population size.

Diet

Seals consume many different types of prey. Over the years, we have conducted several studies on grey seal diet using data on:

diet composition
seal abundance
seasonal distribution
energy requirements

To gather data on seal diets, we use a combination of methods.

For example, we examine fish bones found in seal stomachs, intestines and feces. While these methods are good for understanding what seals recently ate, they have limitations with regards to :

determining seal diets throughout the year
locating the areas where the seal fed
different prey species (some have fewer bones than others) or seal feeding behaviour (seals do not always feed on bony parts)

Given some of these limitations, scientists have developed newer means of studying seal diets using chemical tracer techniques. For example, Quantitative Fatty Acid Signature Analysis is used to analyze specific fatty acids found in seal blubber or muscle to determine the seal's diet composition over weeks or months.

We also analyze the deoxyribonucleic acid (DNA) found in stomach contents of harp seals to identify what kind of prey they have eaten. We can match the stomach contents to common DNA markers of harp seal prey, such as:

krill
capelin
Arctic cod
Atlantic cod

All the data collected gives us a better understanding of the different types of prey seals eat over time, where they feed, and provides information on fish populations as well.

Movement and behaviour

Seals are mobile and feed on a variety of prey. To estimate the effects of seals on fish, we need to understand where they go and how they move to different areas in different seasons. We use satellite tagging to track movement and monitor behaviours of grey seals in the Gulf of St. Lawrence and harp seals off the coast of Newfoundland. This gives us valuable data to evaluate the potential impacts of climate and ecological changes on seals, and improve our understanding of:

habitat use
diving behaviours
migration pathways
interactions with key groundfish stocks

Grey seals and cod

We study the relationships between grey seals and other parts of the Atlantic ecosystem, including Atlantic cod.

The amount of cod in a seal's diet varies widely between locations, seasons, age, sex and cod availability. A single adult grey seal can eat up to 2 tonnes of prey per year, and in certain areas, cod can represent up to 50% of this diet.

The lack of cod recovery in the southern Gulf of St. Lawrence appears to be due to past overfishing and the current high mortality of larger cod. Our studies have shown that grey seal predation is now limiting the recovery of Atlantic cod and may account for up to 50% of natural cod mortality in this region. However, similar results have not been found in other regions.

We will continue to study the interactions between grey seals and cod in Quebec and Atlantic Canada to better understand these ecosystems.

Impacts of climate and ecosystem changes

We can study the impacts of climate and ecosystem changes on North Atlantic seals by:

using drones to monitor changes in populations, body condition and reproduction
studying the impact of changing sea ice conditions on:
- the location of harp seal pupping sites and how it relates to ice thickness and availability
- harp seal pup survival

This work is tied to larger questions about changes in the ecosystem, such as less sea ice and warmer water, and how they affect prey species.

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