On November 4th, 2025 secondary investigator Jim Winter spoke with Dr. Mike Hammill and together they explored Hammill’s experiences working out of the Quebec region on seal research as a top scientist for Fisheries and Oceans Canada. Part 2 of the Winter-Hammill interview covers themes such as changes in seal breeding and migration in the Gulf of St. Lawrence, seal-fish and seal-shark relationships and their ecosystem implications, and differences between grey and harp seal adaptability.
Part 1 of Secondary Investigator Jim Winter’s interview with retired government scientist Dr. Mike Hammill is available here:
[Continued from Part 1]
Winter: Now the other species of course that you deal with in the Gulf and you directly deal with is the grey seals…the word explosion and seal population has come up to describe the grey seal population … but I don’t like that word because they don’t explode. They just grow a bit 12% maybe, but a maximum increase of 12% per year is rapid and the population theoretically will double every 6 years. In practice food, space or things like breeding space become in shorter supply, which we call resource limitation. That means that pup survival declines, pup production declines so the rate of growth slows until they get to some maximum where adults also start to die because of some resource limitation.
Hammill: In theory it doubles every six years, so.
Winter: Increasing in their population and the impact of that is going to have an effect on something. They, like harps, continuously eat a lot of fish as well. You’ve done a lot of work on grey seals, I believe.
Hammill: Yes.
Winter: What do you see happening there? First of all, do you see the growth as a continuing thing or can it reach a max? Like the old adage about a herd of deer will reach the maximum population that its habitat can sustain that kind of idea.
Hammill: We’re getting close to there. I have noted that the grey seals have increased a lot of over time. There again, I’ll back up a little bit. When I started we had grey seals, they were pupping on the ice and in the Gulf the pupping was on the ice. We had a larger proportion of seals born in the gulf than on Sable Island. Sable Island at the time did not have much hunting, but they stopped the little bit they had and pup production on Sable increased rapidly. In the meantime there was always more hunting in the gulf and there were likely some other factors, so the gulf did not increase much, but Sable did.
So actually Sable Island is now the most important herd in Eastern Canada, whereas the Gulf has increased, it seems to on a much slower rate, probably because it’s always been hunted a bit. When I started 90+% of pups born in the Gulf, were born on the ice. Grey seals also pup on the ice in the Baltic Sea, but generally one can say the gulf ice breeding grey seal situation was kind of unique and I had hoped to exploit it using collaborations with universities and supporting graduate students. Then around 2005, ice conditions started to deteriorate and become more unpredictable. I had to drop the idea of ice breeding from my program.
Winter: But grey seals, historically different populations have pupped on land. This wasn’t a new phenomenon with grey seals.
Hammill: That’s what most people think, of them as a land breeding species, but there are two areas where they do pup on the ice. One is the Baltic Sea and the other is the Gulf St. Lawrence. So it’s something that was a bit unusual, something to try and from a science or research aspect to try and see what the impacts of this different habitat might be, but this didn’t turn out. So now they’re all born on islands in the Gulf of St Lawrence, at least 90-99%. And this has led to some colonies becoming quite important as pupping sites. For example, Isle Brion or Brion Island in English, is located north of the Magdalen Islands. Pictou Island is between PEI and Nova Scotia in Northumberland Strait. When I started often we would see seals on the ice near Pictou Island. When the ice became less predictable the seals started to use Pictou Island as a pupping area and now it is a major colony.
Winter: It changes the mortality aspects as well, by breeding on land, I mean.
Hammill: It does. It’s hard to say if it’s better or it’s worse. You had if the ice breaks in for grey seals, it’s tends to have a slightly higher mortality because the pups don’t quite do as well as a harp seal pup. At the same time, if your land colony is crowded, you get more disease, more injuries because the males are quite aggressive. They’ll bite the pups and kill the pups. So it’s hard to see, you know, is it overall better? Is it overall worse? It’s different. That’s the way it is there. But we see the overall level of grey seals has leveled off probably because, like the harp seal, pup mortality has increased or first year mortality has increased I should say and when I started we estimated that the early mortality of grey seals was maybe 30%. Now we figured suffers around 70 to 75%. So we’ve seen a big change and this is probably in response to the idea that they’re eating themselves out of house or home or at least they’re running into some sort of challenges for resources. I don’t know, but getting into your point, the grey seal, when we started our work, we did a lot of work on diet. Grey seals eat mostly fish, so it is easier to study diet by looking at gut contents. Harp seals eat fish and a lot of invertebrates, shrimp like prey which are harder to enumerate and identify to species due to digestion.
Winter: Yes, crab, et cetera, yes.
Hammill: So it’s easier to detect fish in the diet than it is to quantify how much fish is in the diet and which species, whereas in harp seals you’ve got always this missing point. Well, the invertebrates are digested faster, so you underestimate their contributions to the diet, but over the years what we worked out is that, and I forget the exact figure now, but grey seals probably contribute to about 50% or more of the natural mortality in cod. At that level they’re a major factor limiting cod recovery in the Southern Gulf and it was fairly clear and I think it’s impacting other species. I think winter flounder’s another one where they’re saying that natural mortality of winter flounder is so high in the southern Gulf of St Lawrence that even if you stop the fishing, it’s unlikely to recover for a long, long time because natural mortality rates are too high and grey seals are probably contributing to this because the winter flounder are an important prey species for them and there’s probably other fish predators that are not helping. But again, you get into this idea of a lot of sharks, for example, but the sharks, that’s a new dynamic because they hit the grey seals as well.
Winter: So just for clarity, for people who may not understand, when you use the word natural mortality, essentially we’re talking about ocean predators.
Hammill: Yes but it could be starvation as well or disease. It’s a bag of things we often talk about when referencing natural mortality, but it’s a bag of a lot of unknowns. So starvation, predation, disease, everything.
Winter: Yes, it could be other things. The recovery of the ground fish fishery in the Gulf is certainly either inhibited or well inhibited, I guess by the predation from grey seals.
Would that be a fair statement?
Hammill: Yes, I usually use the words limited, but yeah, limited by, but it seems to be a single most important feature.
Winter: We’ve noticed on the West Coast here [in Newfoundland] we see harp seals and grey seals too or harbour seals going up estuaries. Do you do you see that in the Gulf region?
Hammill: Yes, usually harbor seals are the worst.
Winter: They’ll go well into the freshwater environment. Is that normal? Is that normal or is that is that food driven? Is there any work done on it?
Hammill: Yes, harbour seals seem to do well. A sort of detailed study on harbour seals living in their migration up the freshwater hasn’t been looked at, but it’s well known that harbour seals do move into rivers. For example, in northern Quebec, we have a population of freshwater harbour seals, so they do quite well. Numbers 300 to 600 or so in a lake system. If you look at for example where I live in Rimouski, Quebec. On the north shore, near Baie Comeau there is a river called Seal River, so at one point in time it is likely that harbour seals migrated up and lived in the river.
Winter: But is that restricted to river seals or do the other seals do it too or on a more ad hoc basis maybe?
Hammill: More ad hoc, I’d say. I mean, what I hate, and like, about biology is it’s never black and white. There’s always a lot of grey. So it’s like somebody said, when did you ever see any whales outside your house? I’d say never, and then that day I was out on the boat and a minke whale sort of surfaced beside us, so you don’t see minke whales very often at Rimouski. So yeah, basically it’s a harbor seal characteristic. It’s not very common for others. I have heard in Newfoundland there are a few harp seals that go up, but I don’t know much about it. For us it’s a harbor seal issue.
Winter: Very good. But the future for the science side of research in the Gulf area with the demise of climate driven, and I don’t know if the word demise is the right word, but reduction in the presence of harp seals, et cetera. Do you think that will impact your ability to keep doing basic research? Will the funding be there based on climate change and predation or something like that as opposed to the hunting imperative that was driving it before?
Hammill: I think it’ll be hard. Well, it is harder because when I started we had a hard time getting regarding mammals on the attention plate of everybody and then we succeeded in getting the seals involved. And it wasn’t just us it was because of the controversy around the fish, around the harvest. But also, I mean this problem of interaction between seals and fisheries has been ongoing for a long, long time so that generates interest. The pendulum has swung. Now the interest is more on the cetaceans, the whale aspect. So people are investing more in the whales in the last decade or so than they have in perhaps the seal questions. And I think obviously the seal people have to try and sell the aspect of how seals are fitting into the ecosystem such as how do they contribute to mortality for commercial fisheries? What are the expected responses to things like sharks, great white sharks? Because it’s not a federal issue, or at least it’s not a fisheries issue, if you have a lot of seals on a beach. I would definitely not go swimming near that beach anymore because there are great white sharks in the water, especially in parts of the Gulf. So this becomes a human health, human safety issue. So it’s not a DFO problem per se, but it’s still a seal ecologist problem.
Winter: They’ve had that problem in Cape Cod, the sharks following to seal.
Hammill: Yes and we did some work with the Americans a while ago and sharks has some serious impacts on seal behavior. So from a strictly scientific perspective, it could be really interesting to see what the seals do in the face of more shark predation.
Winter: Big time.
Hammill: What are the implications for the ground fish recovery, too? So I think the greatest interest for research has been more of the large whales, right, in the last decade. Seals have probably gone down a little bit but they have not disappeared. The department still supports a lot of people in Eastern Canada. It’s just harder to get some funding maybe, but they have to try and sell it. You have to try and sell it more such as what is the role of the seal in the marine ecosystem? What is the importance of seal as a commercial fishery?
Winter: Exactly. So the predation aspect becomes a thing and possibly, as you said, the shark presence in the Gulf and we’ve noticed a little bit, not that much. Is that water temperature driven?
Hammill: Yes, I think it is several things. They’ve always been here, I think either because of water temperature or species like the great white protection, they have increased and are expanding.
Winter: Territory expansion and temperature. If you were at the beginning of your career these days and you were a young man looking for career advice, would you say, this is a field that might be really interesting for a career?
Hammill: I think so, at least in the Gulf. What’s nice about the Gulf is we don’t have the most of anything, but we have everything. So for example, in Newfoundland you’ve got the largest hooded and harp seal herds in the world, but you need a 200 foot boat to access them for much of your work. That’s expensive. For grey seals, the biggest herd is in on Sable Island, but you need a helicopter and aircraft to access it. We’ve got grey seals in the Gulf. You get in your truck, you drive for five hours, you put the boat in the water and you can catch all the grey seals you want. Or you can go hunting if you want to do your sampling. Or you take a ferry to the Maggie’s and you’ve got excellent conditions to get to harp seals. We used to have that. It would take a helicopter from the island, but a helicopter flying one hour out and one hour back is a lot cheaper than an icebreaker at $50,000 a day. So the Gulf has always been a really cool place because economically it cost you, relatively speaking, nothing and yet you’ve got a diversity of species to play with. So I think in Quebec region, in our region, I’d say yes it’d be a great thing to do, to come and work on it and but you have to orient your program towards equal ecosystem aspects. I think it’s not so much the commercial aims.
Winter: Well, you’re retired now. You’ve had a good run at it.
Hammill: Yes, three years now. We had a good run. We had a lot of fun…It was easier to do research where we were because the logistics were simpler. Not to say that Newfoundland is not an interesting place. There’s a whole bunch of stuff that’s really cool there that could be done, but it’s a different, different philosophy, different way of thinking.
Winter: Right, and a different expense venue.
Hammill: Yes, you have to look at it differently that aspect.
Winter: That’s great. Mike. Thanks very much. I appreciate you taking the time.
Hammill: Thank you.
Seals, Stigma and Survival 