The harbour porpoise is the only cetacean native to the cold waters of the Baltic Sea. But its small population is in trouble. Lauren talks to Ida Carlén, who is working with the NGO Coalition Clean Baltic to save the last individuals of this little porpoise that still call the Baltic Sea home.
Ida Carlén has always been interested in marine mammals. When she discovered that an endangered population of a small cetacean lived in the Baltic Sea just off the coast of her native Sweden, she knew she had to do something. Ida now works with the European NGO Coalition Clean Baltic to help the Baltic Sea's only cetacean ─ the harbour porpoise.
References & Further Reading
– Coalition Clean Baltic’s petition
– Map of states bordering the Baltic Sea
– Ida’s Research
– What are PCBs?
– What is DDT?
– The research paper about PCBs in BSHP and infertility
– EU life Programme
– Restrictions on PCBs in the Baltic Sea (HELCOM)
– Top down vs bottom up
Host & Executive Producer: Lauren Hartling
Guest: Ida Carlén (Coalition Clean Baltic)
Audio Engineering & Editing: Marcus Wernicke
Theme Song: Black Rhomb - River of Time (under license)
Additional Music (used under license):
Watching the Stars by RimsyMusic
Illuminated Moments by Denis
Refuge by Dan Phillipson
A Hope for New Beginning by Evocativ
Sound effects under license from soundsnap, Ojoo Limited
Introduction Lauren: Hello and welcome to Not a Dolphin. My name is Lauren. Hartling joining you here for another episode about these teeny little cetaceans. We’ve had a lot of time to explore everything we could about vaquita a super endangered cetacean found in the Sea of Cortez. This episode is also going to be focusing on a threatened group of cetaceans. In particular, a population of harbor porpoise found in the Baltic sea. I was very lucky to be able to have a conversation with Ida Carlén. She’s a researcher from Stockholm university in the department of zoology, and…
Lauren: Hello and welcome to Not a Dolphin. My name is Lauren. Hartling joining you here for another episode about these teeny little cetaceans. We’ve had a lot of time to explore everything we could about vaquita a super endangered cetacean found in the Sea of Cortez. This episode is also going to be focusing on a threatened group of cetaceans. In particular, a population of harbor porpoise found in the Baltic sea.
I was very lucky to be able to have a conversation with Ida Carlén. She’s a researcher from Stockholm university in the department of zoology, and she has many years of hands on experience, collecting data, studying these animals and even fighting to raise their profile to help better protect them.
So let’s dive right in.
Joining me today is Ida Carlén. and, eh, welcome Ida.
Ida Carlén: Thank you. Thank you, Lauren. And I’m so happy to be here.
Lauren: I’m so glad that you were able to join us. I was wondering if you could kind of introduce your job title, what is it exactly that do
Ida Carlén: I am currently at Coalition Clean Baltic, where I do policy advocacy. Mainly on the Baltic harbour porpoise, which is an endangered population of porpoise here in the Baltic Sea. Uh, I’ve been working with the Baltic porpoise since 2008, approximately. Uh, so it’s, it’s been a while now, and I’ve been involved in some research projects and so on, on this, on this population.
How Ida Got Started
Lauren: Ida, what got you started on working with porpoises in the first place?
Ida Carlén: Oh, uh, that goes back a really long way. When I was a kid, I loved marine mammals. And I just really didn’t know. I don’t, I think many people around the Baltic Sea, you don’t even know that there are whales in the Baltic. So I always wanted to work with marine mammals. I didn’t really think that could be a job, but when I found out that we have the harbour porpoise in the Baltic; it’s, the only cetacean that actually lives in the Baltic year-around.
And when I found out they were there, I sort of felt like I had to do something about the situation that they’re in because there are so few left. So, um, yeah, it’s, it’s been a long time dream and here I am.
Lauren: How, how long have you been working? Uh, studying Baltic Sea harbour porpoises.
Ida Carlén: Yeah. So I started for real in maybe 2008, so that would be like 15 years or something.
Lauren: It feels like yesterday.
Ida Carlén: yeah, let’s say that or like a hundred years ago.
Lauren: Is that’s true
Ida Carlén: but Yeah.
I, I started before that being very interested. I studied marine biology and then I did my master’s thesis. I wanted to do something with the Baltic harbour porpoise, but I somehow ended up on Zanzibar, uh, doing a piece on, on the dolphin populations around there and how they share their habitat.
So that was sort of my way into cetacean biology. Um, and then eventually I got involved in this big European project to look at the distribution and abundance of, of the Baltic harbour porpoise. And that was in 2008. We know very, very little about how many there were, where they lived. We thought that they might be mostly around the coast of the Baltic proper. so we learned a lot during that five-year project, which ended in 2015.
Baltic Sea Harbour Porpoise: Pollution and Bycatch
Lauren: How long have you kind of known that the Baltic Sea harbour porpoise was facing dangers in its, in its habitat of the Baltic Sea.
Ida Carlén: I mean, scientists have known for decades. I mean, when I learned that there was a porpoise in the Baltic, I also, at the same time learned that they are threatened and that’s why we don’t see them. And that’s why people don’t know they’re there because you see them so rarely. So people had kind of forgotten that they exist.
Lauren: Wow. So what exactly, are the challenges that they’re facing?
Ida Carlén: Basically the Baltic porpoise had started to decline in maybe the 1950s or 60s and this was, uh, probably a twofold problem. We know that in the Baltic, the environmental contaminants became really severe, uh, with the levels of especially PCB and DDT. And we’ve seen other species being really hard hit by that fact. So for example, the three seal species that we have in the Baltic, they were severely decimated in the 60s and 70s by especially PCB because the skeletons are deformed and, and the females become infertile because of PCB.
Ida Carlén: Uh, and it’s only reasonable to assume that porpoises were hit as well. But we haven’t really had any studies on porpoises to look at at that in the Baltic. However, there is, uh, study from the UK with several studies from the UK that shows that females –female harbour porpoises, become infertile as well because of PCB. And given the fact that the Baltic Sea, which is a very enclosed sea, has a lot higher levels of PCB than for example, the North Sea, where this other study was made. That means that we can expect that the Baltic porpoises have, uh, any bigger issue with PCBs than the porpoises due in the North Sea.
Lauren: Just an aside about what exactly PCBs and DDT are. PCBs were used in things like electrical transformers that helps us get power to our homes, uh, in paints and even things like silicone while DDT was used as a chemical to kill biting insects, specifically mosquitoes as a way to combat malaria.
Researchers started to notice that these very large human made molecules were ending up in the environment specifically in the bodies of animals like marine mammals and porpoises. These chemicals can actually stay in the fats in the adipose tissue and can affect not only the health of the animal they’re in, but can be passed down by generations.
These chemicals were identified as being incredibly dangerous and in the United States, they were banned in the 1970s. However, I will attach a link to a research article that came out in 2021 that identified PCBs in harbor porpoises living in the oceans just off the coast of where the Baltic sea harbour porpoise is.
So, unfortunately this is still a present day problem for these animals.
Ida Carlén: So the Baltic Sea is a very enclosed sea and it’s a brackish water sea because we have not very much inflow from the big oceans of saltwater. And we have a lot of fresh water run off from the areas around.
And that means we have a brackish sea, which is doesn’t have a lot of exchange of water with the big ocean, which means any contaminants and stuff that we humans put in the water. It stays here. And so the levels of environmental contaminants are often a lot higher in the Baltic than in the, in the big world oceans, so to speak.
Ida Carlén: So this study could show effects of PCBs on female porpoises in the North Sea. And the levels of PCB in general in the Baltic is about 25 times higher than in the North Sea.
Ida Carlén: Yeah. So we, we can, we can assume that we have a big problem with infertility in this population.
So that’s, that’s one of the, basically two main things. The other threats, as we know, I mean, bycatch is a threat for cetaceans all over the world.
Ida Carlén: And, uh, in the sixties, maybe fifties or sixties, uh, nylon gillnets are introduced globally.
And that means you can increase effort because they’re easier to handle. They’re easier to fix if they break, they’re cheaper to use, and also they, they don’t break as easily.
Ida Carlén: So the bycatch probably increased quite a lot in that time when, when nylon gillnets were introduced. And that’s the other problem that we still see in the Baltic that bycatch, we don’t really know how much by-catch we have, unfortunately, uh, because bycatch monitoring of such a small population is very expensive. So there isn’t much monitoring going on at the moment and we’re pushing quite hard to, to get that happening.
Ida Carlén: But, uh, we know that even even one animal per year means that this population is going to have a hard time recovering.
Lauren: So I, I don’t think I realized that the Baltic Sea was a brackish water body. Um, are you finding that the Baltic Sea porpoises is their diet very different from other porpoises because they are in such an enclosed brackish system?
Ida Carlén: Uh, we don’t know for sure. Um, so this is quite interesting there are… Today, there are so few porpoises that we can’t really carry out any studies that needs specimen collected. I mean, we could gather all the stranded animals and all the by caught animals, but that’s going to be like maybe one per year. There are so few animals found dead because there are so few left.
Um, so any of that kind of studies we can’t really do in the Baltic, so we have to go to other areas and try to sort of incur what we might have in the Baltic.
Ida Carlén: Um, what we do know is that in the Baltic Sea region, sort of, we have basically three populations of porpoises and the Baltic proper porpoise, which I’m talking about, which is the one that’s endangered, uh, is in the inner part of the Baltic Sea. And then as you move out towards the North Sea and the North Atlantic, you have another population that’s called the Baelt Sea population, which lives basically in Danish waters.
Ida Carlén: And so what, what scientists have done over the years is look at the difference between those two populations basically to look at, we have very few porpoises in the Baltic. But over quite a few studies, we have shown that the Baltic proper population is a separate unit. And when you look at the differences between the Baelt Sea and the Baltic Sea populations, is that they’re slightly different, morphologically.
Lauren: Oh, cool.
Ida Carlén: The Baltic porpoises eat more pelagic fish. And then there is also old stomach content analysis from the Baltic that says that they eat herring, sprat, cod and some other species, but mostly pelagic species
That specific population is listed as critically endangered by, by the IUCN. While the Baelt Sea population is not.
Lauren: And so the Baltic Sea harbour porpoises, they’re the only ones living in this brackish water system. The other ones are outside of that brackish system in, in a different sea. Okay. So, so you’re talking about how critically endangered they are. And similar to the vaquita how hard it is to count an animal there’s not a lot of.
And as you’re saying, if only one per year is coming up in bycatch, which again, any loss of any individual is, is horrific. Um, do you have a rough estimate of how many Baltic Sea harbour porpoises you think are still out there?
Ida Carlén: Yes. So. Uh, as I mentioned, I started my sort of career in the Baltic harbour porpoise world, uh, in 2008, when we started drafting a project plan to look at the distribution and abundance of the Baltic porpoise, because we didn’t really know anything at that point, and between 2010 and 2015, we carried out that project, which was funded by the EU Life program. Usually, when you do a survey or want to count how many cetaceans there are in an area, you do either line transect surveys, either with a boat or a plane. But the problem is if you do that in the Baltic, you’re basically not going to see any porpoises at all. Um, uh, because there are so few, so you might have one or two sightings over the few days that you’re out. So we had to find a different method to look in the Baltic and what we realized was basically the only way was what we call passive acoustic monitoring. Uh, so over two years, from 2011 to 2013, we deployed 300 porpoise click detectors in the Baltic Sea. And that’s 300. That was, and we had them running for two full years to get, you know, full, full information on where the porpoises are when and how many there might be. Um, so that was a huge effort in, in field as field work comes.
Uh, and this was done in cooperation with all the Baltic Sea countries. So all the countries around the Baltic Sea were involved.
Lauren: When Ida talks about the Baltic sea countries, she’s referring to nine different countries, including Denmark, Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Poland, and Germany. We’re gonna include a map of the Baltic sea countries in the show notes for you to check out.
Ida Carlén: Um, and we had national teams going out every three months to change batteries and change data cards in these porpoise click detectors. And they, the Swedish team had 99 positions to take care of. And they were out at sea, basically here out for two years.
Lauren: Oh my gosh.
Ida Carlén: There’s and this was a huge effort. Anyway, based on the detections we had, um, we could calculate or look at the distribution of animals in the Baltic. and it’s very interesting because we, we found out things that we had no idea about.
I mean, the only information that we had before this project was that was the incidental sightings around the Baltic. And obviously they occur where people and porpoises overlap, which is basically around the coastlines where people go with their, their boats and so on.
Important Population in the Middle of the Baltic Sea
Ida Carlén: But what we realized when we were starting to analyze our data, um, was that there is an area in the middle of the Baltic proper where we had a lot more porpoises than we have along the coastlines.
So there is a, quite a big area in the middle of the Baltic Sea, which is really important to, to the Baltic harbour porpoise. And it seems that they spend especially summer there and summer is when they reproduce when they mate and when they give birth to their calves. So this area is really, really important for this threatened population.
Lauren: Wow. Do you think they’re in the middle? Just because they’re away from people, like, do boats go out into the middle or do you think, do, do you have any idea of why they might go to the middle?
Ida Carlén: um, obviously we don’t know exactly, there in this area, there are offshore banks, so there’s deep areas around, and then it’s a bit more shallow in some places in this area. And we think that might be one of the reasons because it’s, um, we also know that fishermen go there to fish because the fish obviously gather around these off shore banks.
So that might be one of the reasons that the access to food is better.
There are unfortunately a couple of really big shipping lanes going straight through. So the theory is more that they have to spend time there because it’s a good habitat for them.
And then they have to live with all the big ships and so on that goes past and it’s sort of worth it somehow for them.
Lauren: So your research started in 2008, or you started designing your research. Did any research on the Baltic Sea harbour porpoise happen before 2008 that you know of?
Ida Carlén: Definitely, there was a lot, done before that, but we didn’t have the technology then. So there has been a couple of surveys trying to come up with an estimate, for example, of how many porpoises there were in the Baltic. Uh, but then we didn’t have access to this passive acoustic monitoring that I mentioned.
Ida Carlén: um, so there was some boat surveys and some, uh, aerial surveys made, but you know, the estimate and the confidence interval becomes very big when you only see one or two animals in a survey because statistics, statistics can’t really deal with that few sightings.
Lauren: So you had 300 click detectors. You were finding that they were spending time in different areas. Were you able to come up with an estimate of, of many animals from, from that survey?
Ida Carlén: Exactly. Yes. There is an estimate and that estimate is that there are between roughly 100 to 1100 animals. And the point estimate is around 450 animals.
Lauren: Wow. That’s a huge range. A hundred to 1100.
Ida Carlén: It’s a huge range. And it’s, it’s because it’s a very complicated calculation and this is the first time it was ever attempted on this scale. And so we were, we were early in this technology, um, and these methods. But yes, we’re very pleased that we have this estimate because supports this population being endangered and, and that we clearly have to do something.
Lauren: Uh, With the passive acoustic monitoring. Did you find that you were able to differentiate one individual from another, with those monitors or is it more a porpoise has passed by and we, and we can hear them, like, can you identify individual or is it based on like a statistical number of clicks.
Ida Carlén: It’s based on the statistical number of clicks and that’s why it gets even more complicated the calculations, but so far we have no way of, of, uh, seeing the difference between individuals.
Lauren: Has there been any photo ID with the porpoises or I guess this is, again, it goes back to the fact that they’re so hard to see from boats?
Ida Carlén: No, in the Baltic,. I mean, I mentioned that the Swedish team that took care of the, of the porpoise click detectors were out at sea, basically two years, they never saw a porpoise.
Lauren: No way.
Ida Carlén: And you imagine these are harbour porpoise experts that spend so much time at sea, and they never even saw one. We know they’re there, cause we could detect them acoustically, but no one saw a porpoise.
Lauren: oh, that must’ve been so upsetting! Those researchers!.
Ida Carlén: It’s frustrating to say the least.
Lauren: Oh my goodness.
SAMBAH… and a follow-up study?
Lauren: Does your team have, hopes to go out and do it again, soon to maybe collect more data recently or, or, or what’s kind of your next step?
Ida Carlén: Yeah. So, the, the first study that I’ve been talking about was called SAMBAH um, static, acoustic monitoring of the Baltic Sea harbour porpoise.
Lauren: That’s a great name.
Ida Carlén: Yeah. Yeah. We’re very happy when someone came up with that abbreviation.
Lauren: Ida talked about how they were hoping to fund a SAMBAH 2 project, but that funding for that project had been hard to find. The first project cost 4.5 million euros, which is about 6 million dollars Canadian. And to do the project again today, it would cost even more money. The goal of this next SAMBAH project is to look at the effect of MPAs or Marine protected areas to see how effective they’ve been at helping protect the Baltic Sea Harbour porpoise.
So if you know anyone who’s got money that they are looking to donate toward a worthy cause perhaps the Baltic Sea Harbour porpoise research project is, uh, where you can direct
Ida Carlén: But there’s also a lot of other issues that we should start looking into, like how fisheries overlaps with, with distribution and how, how an underwater noise can, could affect, um, the animals and so on.
So there’s a lot of other knowledge that we need to, to look at. but unfortunately we haven’t been able to find the funding, which is, um, yeah, it’s a big issue right now.
Is Anyone Else Looking Out for the Baltic Sea Harbour Porpoise?
Lauren: Is there any buy-in from the government or from other people, like, is there any interest from anyone other than researchers to, to protect this species? Have you, have you kind of gotten that sense as you’ve been, been doing this work?
Ida Carlén: In 2015 SAMBAH 1 ended and then in 2016, I went into the NGO world. And since then I’ve been, acting as an NGO to try and push policy, development to protect this population. And we have seen some movement, the European commission in the EU, uh, are pushing countries to do something. And the countries are starting to see that they have to do something. So we actually just recently had a few MPAs closed for gillnet fisheries, which is the type of fisheries that would cost most of the bycatch. Um, we need a lot more to be done, but at least this is, step that we have been waiting decades for.
Lauren: It’s so unfortunate that, you know, you’re seeing these changes happen so fast and that it does take that much time to see action happen. Like that’s, we’ve been hearing it across the board with, with other species and people we’ve talked to that’s, that’s gotta be really heartbreaking for you as a researcher watching that happen.
Ida Carlén: Yeah. I mean, I found about a year ago, I found a document from 1976 where the quote that the Baltic porpoise is endangered.
And that is as old as I am. So it’s been 46 years and now things are happening, which is really sad that it’s been this long.
Is There a Way for People to Report Sightings?
Lauren: You know, you’re talking about how difficult it is to see them, how even researchers who were out for two years, didn’t see them. And I’m laughing at the frustration that they must’ve felt, but, um, is there any sort of tracking system?
So if, if you know, the average person, like a citizen science kind of thing, is there any way that people can report their sightings or even, is there any way that people can report that they found a dead animal or that one was caught in bycatch?
Ida Carlén: so in most countries there is some way to report if you have seen a live porpoise, or if you’ve seen a stranding and in most countries, I would say if you find a stranded animal, it is taken care of somehow. So someone comes to, to take care of it and take samples. And if it’s fresh enough, do a full necropsy. But it …it does vary quite a lot and we get extra. Like I could basically say we get no fresh samples in the Baltic. It’s extremely rare.
Ida Carlén: The Baltic harbour porpoise has been a source of conflict in with fisheries, as you can imagine, because we always say that bycatch is the main threat and then fishermen are righteously frustrated because that means that they’re going to have to do something and it’s going to infringe on their livelihoods basically.
so it’s been difficult to get fishermen to report sightings or by catches. It happens sometimes that a fishermen reports, a by catch. And then obviously that, that specimen is very valuable to science.
Lauren: It’d be so fresh like you say…
Ida Carlén: yeah, exactly. Because if it’s not fresh, it’s difficult to get a lot of information from it. You obviously take genetic samples, and maybe, uh, some other things, but it’s, it’s quite difficult.
Lauren: Have you ever heard of any, um, Baltic, sea harbour, porpoises, stranding and, and being successfully re-released or is that, is that something that’s possible there?
Ida Carlén: I haven’t ever heard of a live stranding at all. Um, there was actually a bycatch in Finland, which is like, I don’t know how small the chances are to get a bycatch there, but it was successfully released alive, which is like one in a billion or something. Um, that’s a few years ago now. I was speechless when I heard it, but it’s amazing at the same time.
Lauren: that’s amazing.
Ida Carlén: Yup. Yup.
Threats to Harbour Porpoise in the Baltic Sea
Lauren: You’ve listed a whole bunch of, of threats that the Baltic Sea harbour porpoise experiences, you were talking about, uh, PCBs . Do you, do you have any idea of where exactly those chemicals were coming from that we’re getting into the Baltic Sea?
Like, was there ever a point source identified?
Ida Carlén: This comes from industries, uh, along, I mean, everywhere. PCBs have been very much used in, in different kinds of types of industries for a very long time.
So it’s not one specific point source it’s just everywhere. And I think you have the same in America. It’s um, yeah, it’s everywhere.
Dramatic Decline in Grey Seals
Lauren: When you were talking about the, the seals were facing these challenges too have, and I, I noticed, I know they’re not your, your focus species, but has there been an improvement in the seal population in the Baltic Sea as well? Or did they experience a pretty traumatic decline as well?
Ida Carlén: They did experience a very dramatic decline. So in like the 1970s or eighties, we had around 3,000 gray seal in the Baltic, uh, which had then declined from, I mean, tens of thousands, maybe a hundred thousand animals, but that’s a happy story because the, the gray seal population has now recovered and it’s up to maybe 40 or 50,000 animals
Lauren: Oh, that’s great.
Ida Carlén: Yeah. So that’s, uh, that’s happy news.
Lauren: Yay. I like when we have those happy stories, get those gray seals backs.
One Species to Protect, 10 Countries to Consider
Lauren: So you had mentioned that currently your work is working with NGOs how difficult is it to, to bring those 10 countries together to affect policy? Like how, how are you finding your current role?
Ida Carlén: Um, actually, because nine of the 10 countries are members of the European Union, what I do quite a lot is work at the EU level with policy there because there is environmental legislation in, in the EU that all countries have to follow. If they’re members.
Ida Carlén: Uh, so a lot of my work is at the EU level. And also HELCOM the Helsinki commission. Uh, we do quite a bit of work there as well. obviously, uh, since I am Swedish and I live in Sweden, I do some work nationally trying to influence our, our policymakers here, but I also have a lot of contact with NGOs in other countries around the Baltic to sort of support them in doing advocacy work in their own countries.
Lauren: right. Are you finding that that has been making a difference? Are you finding a bit more buy-in from those other countries?
Ida Carlén: Yes, I think so. I think it’s the work that we’ve been doing at coalition clean Baltic for the last six years has made a difference. So it has raised the awareness, both in the EU and also in the different countries. And I think obviously if you raise the awareness of the European commission, the commission is gonna start pushing the member states to do something.
And that has obviously helped. But I do think I’m very happy that it feels like we’ve actually done something good here that it feels like we did. It’s made a difference that the work that we’ve put in.
Lauren: No, of course. And I’m, I’m wondering as you’re explaining that and getting more people on board with the advocacy work that you’re doing, are you finding that. You know, the story of the vaquita is still pretty fresh. Um, I think maybe in our listeners minds, but also maybe for globally, are you finding that that is kind of helping you, that you can kind of show a story of a species that is declining even with the attention.
So you’re trying to bring attention to this. Are you finding that it’s kind of helping maybe spur people into action to protect the Baltic Sea harbour porpoise?
Ida Carlén: I wish I could say yes, but I’m afraid. Not really. Um, if there wasn’t legislation and if we weren’t so vocal, I think a lot of people would rather just forget that they would have to do something and that this is, uh, a critically endangered population. I mean, obviously there’s always people who do care, which is very nice,
Ida Carlén: but there is, um, Yeah.
it’s really hard.
Lauren: I’m, so sorry. That’s um, uh, that must feel like you’re I heard someone use the term pushing a rock up a hill and I imagining I’m imagining you with your work in yeah.
Ida Carlén: yeah, it’s, it’s so sad because so few people around the Baltic Sea know that we have a whale in the Baltic. And if the, if the public doesn’t even know about the species that you’re trying to protect, the road is very long for having the decision-makers care about it. You first maybe have to make the people care about it.
Lauren: So again, you know, 10 countries surrounding the Baltic Sea, do do many people know this animal? I mean, I mean, obviously through your work, they know they exist, but do you find, you know, the average person you, you meet, do they know that Baltic Sea porpoises exist?
Ida Carlén: Um, we actually did a small study on that, uh, about a year ago where we had a few hundred people in Europe answer a survey, if they could recognize some animals. And among those animals were a porpoise and very few could identify it as a porpoise. Most people think it’s a dolphin. Um, and I would say no.
I mean, it’s a very, very small part of, of the people around the Baltic knows that there is a whale in the Baltic.
Ida Carlén: Yeah.
The Value of Saving the Baltic Sea Harbour Porpoise
Lauren: You’re focusing on a population that is genetically unique as, as you mentioned, you know, when we’re talking about saving species, can you kind of speak to the importance of saving? Why should people care about saving a small population? That’s not a separate species.
What’s the value of saving a subpopulation.
Ida Carlén: Yeah. Well, first of all, in my world, in my book, we, as humans doesn’t have the right to just make something disappear. They have the same rights as we do to exist.
Ida Carlén: Um, the Baltic porpoise has once been a very important part of the Baltic Sea ecosystem. And if we lose them, they’re not going to come back. I mean, it’s, it is a separate population that the neighboring population in the Baelt sea doesn’t spend much time in the Baltic. Porpoises are sort of site-specific.
So they come back to the area where they were born to breed. And if we lose the Baltic proper population, it’s not going to come back. It’s not going to be replaced by any other population.
Overlap Between Populations
Lauren: I guess I hadn’t thought of it until now. When you just mentioned that, do you find, historically that there was, an, overlap between the Baelt sea and the Baltic harbour porpoise?
Would the Baelt see come into the Baltic at all?
Ida Carlén: Yes, there is an overlap between the two populations. So it seems that during summer, the Baelt sea population moves some of the animals move eastward and they can enter the Baltic, uh, not, not all the way, but a little bit into the Baltic, proper that we see. Um, and also during the winter, Baltic proper harbour porpoises move to the west, which is closer to the Baelt Sea population. And especially, I mean, now we haven’t had a severe ice winter in a very long time, but obviously a lot of the Baltic can freeze over completely in the winter and then porpoises would have to move to the Southwest to get away from the ice. So yes, there is spatial overlap between the populations, but since they breed in separate areas, they become genetically a separate
Lauren: That’s so cool to imagine. Um, you know, here on the west coast of BC, we have a couple of different populations of killer whales, and it’s a similar thing where they, they all look like killer whales, but they are different populations. And I remember asking a researcher, if they’ve ever seen the residents, which are fish eaters and the Biggs killer whales, which are the mammal eaters in the same place at the same time. And they said, yeah. And it was kind of like, um, they kind of go radio silent as they pass each other, like super awkwardly, which I thought it was just kind of fun to imagine them being like, oh, don’t look at them.
Um, I’m imagining porpoise is doing the same thing, but on a smaller level,
Ida Carlén: Yeah I, we don’t know what if they interact at all. We have no idea. I mean, It’s, it’s interesting.
Lauren: With, with your research, have you ever collected acoustic data besides the clicks? Have you ever, um, I know, I know harbour porpoises tend to vocalize at a much higher range than other cetacean species. Have you ever been able to collect vocalizations from, uh, porpoises at all?
Ida Carlén: uh, to my knowledge, the only sounds that they make are clicks, but there are communication clicks and there are food looking clicks. There are, um, yeah, different types of clicks basically. Um, and, uh, I have a friend and colleague in Denmark who was actually looking at trying to identify the, the communication clicks in the type of data that we collected in, in the SAHMBA project.
Lauren: well, that’s exciting.
Ida Carlén: Yeah. It’s really cool.
Lauren: Oh man.
Ida Carlén: But it’s just starting. I mean, that, that type of research is very new.
Lauren: Right. And as you’re saying, if you already have a small population and it’s so hard to find them in the first place, that must be such a difficult research project.
Ida Carlén: If in the future we can probably use the data from the passive acoustic monitoring to look at this as well. Um, but you might want to have to start with a study where you can actually see what the animals are doing at the same time that you’re, recording sound and looking at their behavior at the same time, to be able to sort of see what they’re doing and know what they mean when they click.
There seems to be evidence for communication clicks, which is really cool.
Lauren: Oh man. It’s so fascinating to me that there’s, there’s so much that we don’t know. And, and, you know, even talking to you here, you’ve been studying these animals for so long and to still have things that we don’t know about them, to me as a biologist, like that’s so exciting, but I know for the general public, that must be so frustrating of like, how do you not know?
And it’s, there’s just, there’s so much to know. There’s so much that we could find out.
Ida Carlén: Yeah, yeah, It’s uh, yeah, there’s still a lot that we need to learn.
Things That Ida Wants People To Know…
Lauren: Is there anything that you really want people to know about the Baltic Sea harbour porpoise that we haven’t talked about yet?
Ida Carlén: Um, so the first is the genetic difference between the, what I said, the Baelt sea, the neighboring population and this critically endangered Baltic, proper population of porpoises, uh, the geneticists say that it is a small genetic difference.
It’s consistent, but it’s very small. And one of the reasons for this small comparably small difference is probably that the Baltic Sea, as it looks today is very, very young. So the Baltic Sea in its present form has only existed for about 10,000 years, which means that on an evolutionary scale, the Baltic proper population is very young. So the fact that it is genetically different despite this evolutionary young age, I think is it’s an explanation that we need to keep in mind because we often hear that it’s not sufficiently separate genetically from, from the neighboring populations and that it therefore might not be sort of worth protecting, but if it’s allowed to survive and continue to grow that genetic difference will increase.
Lauren: Have we kind of seen that they are like, Are they a Keystone species? Are they, um, important to maintaining that balance there?
Ida Carlén: unfortunately given that the population is so small, even though at one point they were probably a very important species in the ecosystem. Um, At this point, they cannot be because there are so few of them that they cannot make a big impact on the ecosystem. Um, but I mean, historically it’s likely that there has been at least tens of thousands of animals or porpoises in the Baltic.
Uh, so they definitely have the ability or the potential to have an impact on the ecosystem. And obviously they’re are an intrinsic part of the biodiversity of the Baltic Sea. Um, they’re, they’re the only species of cetaceans present in the Baltic, breeding in the Baltic. So they are a very, I think, a very important part of the Baltic biodiversity,
Ida Carlén: um, and speaking of the ecosystem, that’s the other thing that I wanted to mention.
Ida Carlén: Uh, so the, Baltic ecosystem has changed a lot during the last decades. And this change is obviously driven by human activities. We have decimated a lot of populations of fish. I mean, the seal population was decimated to 3000 animals. They’re now back, but when the seal crashed, then the cod stock crashed.
So there are basically no cod fisheries left in the Baltic because that stock is gone. Basically we’re now slowly decimating the herring stock in the sprat stock. Over fishing is a very serious thing in the Baltic. At the same time, we have environmental contaminants. That’s affecting the ecosystem.
Obviously we have eutrophication, which for the same reasons that us and my own contaminants is a big problem in the Baltic. Eutrophication is also a big problem because whatever we put in the Baltic stays there. There is no exchange too. I mean, there’s a very small exchange of water with the big oceans, which means if we put nutrients into the Baltic Sea, they stay there.
So the ecosystem has seen in the last few decades or flip from, from top down governance like, the predators governing the ecosystem to bottom up, which is a big change.
If you imagine an ecosystem like a triangle or a pyramid at the bottom of the triangle, you’re gonna find your producers, your photosynthetic organisms that rely on the sun to produce energy and they themselves get eaten. At the top of the triangle. You have your carnivores, your consumers. They are going to be consuming the things beneath them.
In this triangle, there’s always fewer consumers than producers. That’s where we get that pyramid shape. A top down ecosystem means that the carnivores, the top consumers are controlling what’s happening in that ecosystem. You have enough predators to keep everything in check, and often if you’ve watched any nature documentaries, um, an African Savannah is a really good example.
A bottom up ecosystem means that the producers, the plants or the photosynthetic organisms have far more of an impact on the ecosystem. This is kind of true all the time, but we tend to refer to bottom up when we are finding that the photosynthetic organisms are crashing, um, at a greater rate than anything else.
Ida Carlén: And looking then from the porpoise perspective where we have the threat of environmental contaminants. We have bycatch, we have underwater noise, and we’re now also starting to worry that the access to high quality prey might influence the population because we can see there are studies showing that the quality, the health of the herring stock, for example, in some areas is quite low.
So the fat content is lower than it traditionally has been in hurry. And that has been shown to influence seal health. So the blubber thickness of seals in some areas have been lower because the herring isn’t as good quality as they should be. There are so few porpoises left that we don’t have the specimens to do studies like that on porpoises, but it’s reasonable to assume that this affects the harbour porpoise population as well. So there’s a lot of things influencing this population.
Ida Carlén: That’s really worrisome.
Is There Hope For The Baltic Sea Harbour Porpoise?
Lauren: No Do you have any hope, uh, for the Baltic Sea porpoise? I know that sounds like a loaded question. I don’t intend it that way, but, um, have you seen any small success that you kind of cling to, or like what, is there anything maybe positive that you can kind of oh, good.
Okay. Yeah. I’d love to hear. Um, I, cause I do find that researchers are these amazing people who see all of this, you know, really difficult stuff, but they’re still so filled with hope and, and I’m glad that you just said yes, I’d love to hear. I’d love to hear your personal hope.
Ida Carlén: Yeah. Now, um, as I said, uh, I think some of the efforts that we’ve been doing in the policy advocacy work has given some, good things lately. And now, as I mentioned, we have these few MPA’s closed for gillnet fisheries, which will hopefully at least decrease the number of bycatches in the Baltic.
Um, and there are National monitoring programs ongoing in the Baltic using passive acoustic monitoring. And some of them see a slight decrease in detections in the last few years. Um, so we don’t know, we don’t have any absolute estimates of abundance since the SAMBAH project, but in relative detection uh, frequencies. We see a little bit of a decrease in some areas. So you really hope that this is true and that a future large-scale survey where we can look at absolute abundance can show that we might have a population that said not at least not decreasing further, but we don’t know yet, but it is a bit of a hope.
More Protected Areas? What About Pingers?
Lauren: Is there a plan to make more protected areas in the Baltic Sea, or is there space for more protected areas within the Baltic Sea?
Ida Carlén: Yes, definitely. So, um, a couple of years ago in May 2020, ICES, uh, the International Council for the Exploration of the Sea came with scientific advice on how to minimize by catch in the ball. Of the Baltic, proper harbour porpoise.
Ida Carlén: Uh, this has been a very important document, obviously over the last couple of years and the closures of static net fisheries that I mentioned have been a result of that document.
Uh, that document also specifies further measures that should be taken to minimize harbour porpoise bycatch. Uh, for example, it’s suggested that we should be using or acoustic deterrent devices on static nets in other areas, except that like, if the MPA is, are closed, we should use pingers in other areas where a static fisheries goes on.
Lauren: a pinger or an acoustic deterrent device is something that you would put on a fishing net or something in the ocean that could be dangerous for marine life. It actually produces pulses at a high frequency. So something in the range that especially cetaceans can hear, and it actually encourages them to avoid that particular thing.
Ida Carlén: That’s been shut down by military concerns from national navies, but we definitely do need to take further measures. Um, so. We are just now looking at what further areas should be closed for static net fisheries to further protect porpoises from bycatch. And there are, there are areas that we identified both in the SAHMBA project and in national monitoring programs that we will be advocating for closing.
Lauren: I wanna thank Ida Carlén so much for her time and her knowledge working to raise the profile of the Baltic Sea Harbor porpoise, and giving us the opportunity to really see more about a species that many people even living around the Baltic sea don’t know exists.
If you wanna get involved yourself we’re going to be including a link to the petition that Ida mentioned, um, going to the EU authorities in charge to try to raise the pro profile again more about this particular species.
I also wanna thank Marcus for his time in helping me to edit and put together these episodes into the final versions that you end up hearing. And if you have any questions about what you’ve heard in this episode or previous episodes, I encourage you to reach out. You can email me at [email protected].
I’d love to hear from you and see what you are thinking about the episodes. And also if there’s anything that you want to know, uh, in future episodes, I hope you had a good time today. And I wanna thank you for joining me and as always, go fluke and learn something.