How To Protect The Ocean
SUFB 090: Great White Shark Abundance and Seasonal Trends in the North West Atlantic Ocean
Continuing with our week about the Great White shark, I thought I would talk about a paper that described the North West Atlantic population in terms of its Abundance Trends during Summer and Winter Seasons. The information in the paper I talk about contains important information that helps understand the species better, which will improve their management for future years to come.
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http://www.speakupforblue.com/session90
Welcome to the speaker for blue podcast session 90 happy Thursday today is research Thursday on the speaker for blue podcast where I Pick a specific research paper. I read about it I analyze it and then I communicate it to you in a way that is really easy to understand and understand the conservation aspects of said paper Today I'm going to continue to this week's theme of looking at the great white shark And we're going to look at the abundance and distribution and trends of the great white shark in the Northwest Atlantic Ocean So that means everything along the east coast of the US, Canada and even down in the Bahamas So stay tuned for this week's episode or this research Thursday's episode of the Speak Up for Blue podcast Welcome to the Speak Up for Blue podcast helping you get involved in ocean conservation And now here's your host loves football so much I mean he really really likes it Andrew Lewin Hey everybody welcome back to another great exciting episode of the speak up for blue podcast your voice for the ocean I am your host Andrew Lewin founder speak up for blue.com Marine Ecologist and self-proclaimed ocean printer and today is research Thursday I am very excited to present to you today's paper Which is called the title the seasonal distribution and historic trends in abundance of white sharks in the Western North Atlantic Ocean I know it's a big title I'll explain it all but it's very important to understand what the abundance and the trends are of great white sharks on the East Coast Which from a different perspective of what we've been talking about before so we're gonna get all into that In just a second before I do I just want to thank our supporters of this show our patreon supporters Claire and Chris jefford. Thank you very much and dr. Judith Weiss. Thank you very much for your support on our crowdfunding campaign to keep this speak up for blue podcast going and allowing me to really dive into a Lot of these projects and a lot of these communication efforts so that we can further ocean conservation So thank you very much for that. So let's get into today's episode like I said It's very important when we talk about a species like the great white shark a very popular species a species that's had a Very bad reputation in the past, but that reputation is slowly changing with a lot more supportive sharks And that support is coupled with a lot more understanding of the great white shark Species its populations around the world how they react where they are and how close they are to us when we're swimming or Just having fun in the ocean. So today we're gonna focus on a paper that looks at the Western North Atlantic Ocean Great white sharks. These are sharks that occur Mostly along the east coast of the US sometimes into the Caribbean Gulf of Mexico and all the way up to the east coast of Canada Nova Scotia, maybe even as top as Newfoundland But really what we're gonna look at is the historical treasure This is a 2014 paper. It was written by Toby H Curtis and Camilla Menkendless John K. Carlson Gregory Skomol Nancy Kohler Lisa Natasha George Burgess John Hui and Harold Pratt Jr. A lot of people on this On this paper, which is great because you see a lot of collaborations and you can I'm gonna put the link up on our show notes of the actual paper so you can see about the authors This is a journal that I got from PLOS 1. It's a journal article And I just searched PLS 1 and I searched great white shark and this one of these these this is one of them that came up That I thought was interesting like I said it was published in 2014 So a lot of the data that's been used for this is actually from 1800s to 2010 and what they did is instead of using satellite tag data is they used Observer data so people on fishing boats People who have caught or interacted with great white sharks through fishing efforts So that's what most of the data that's what all the data entails It doesn't entail the satellite tag sharks that you see today and you hear about a lot in the news All the different media outlets that you see You know where you actually see the patterns that they focus on this actually is other data that people have used in the past But it encompasses 210 year periods So that's kind of an interesting data set. It's the largest data set compiled for the northwest Atlantic So that'll be interesting to see what they're looking for and what are they looking for while they're looking for spatial trends Seasonal trends in where these sharks live is they're specific and why looking at the reason why they look at all different Life stages so they look at juveniles. What would be called YOI which is young of the year Essentially first year of the fish and of course adults, so we're going to find out all this kind of data so essentially What they did is they they look they compiled all this data and they kind of categorized where the data was found What time of year the shark was found and where they were found And then they looked at what the temperature was and different environmental factors was to see if there's a pattern there So what they noticed in this System was that or in the study was that there is definitely a trend a seasonal trend in abundance and Essentially what would happen is the species would be found in the northeast Northeast United States off the coast of the northeast United States Basically, Massachusetts, New York main Area mostly caught focused in the in the Massachusetts area and New York area and they noticed that all life stages were found in there And they noticed that the temperature of variance used is was actually no, sorry So in the summer they would be found up north where the waters were A little cooler in the winter most of the observations actually happened in the south so the southeast United States Florida Georgia They'll those areas usually the northern part of florida Cape Canaveral area And then sometimes so sometimes even in the Gulf of Mexico near Tampa Bay Area and other times Scattered around the Caribbean but not very not very many times And what they noticed for both of those Observations like those seasonal observations is that the temperature ranges the sea surface temperature range tended to be Between uh Where is it here between I had the temperature shoot I think it was between 14 degrees and 20 degrees Celsius Uh, let me just see to make sure to confirm that number as I kind of talk along here Uh, sorry There we go discussion Yeah, I'm sorry here So it was between 14 degrees and 23 degrees Celsius was the temperature range that the northwest Atlantic Great white shark population was actually found in Now whether that is either in the summer or in the winter months, so those are waters That's what the temperature range is now there overall the species has known to be in temperatures between three degrees and 28 degrees So quite a large span of temperatures there, but this Study was found that the sea surface hunter was found to be between 14 and 23 degrees So that's kind of interesting. It's more of their upper upper middle limit of where they like to be so that's I find that Quite interesting. Uh, and then they said the temperature was probably secondary of where they wanted to be found Primarily they they suggested that the the sharks were found in areas where there there was food availability and prey availability Now they mentioned That the y o y the young of the year tend to be really closer in shallower waters closer to the in the summer closer to the new york bite area Where they're tend to be prey that they could actually Uh eat so they would do a lot. They would eat a lot of demersal fish Pray and teleosts and elasmo brain. So other you know other kind of Other kind of fish and and and uh cartilaginous fish. So uh, that was kind of kind of interesting and they were found in waters Less than 50 meters deep. So you know off that broad New York bite area Um, so this tended to be uh, what I what they identify as a primary nursery habitat So that has implications for management, uh, which we'll talk about in in later on in this episode Um, and they noticed that other Areas that they tended to focus even though they could be anywhere in the northeast on that summer Uh, they tended to be where some whales would be so whale carcasses They tended to be found there eating nose Uh, they tended to be along cape cod where there's an emerging or re-emerging gray seal population So that's why lately especially lately we found that they've been Hovering around uh cape cottage because of the gray seal populations coming back So it's not because of recreational swimming is popular, uh, for human species It's actually the fact that there's a seal population that's emerging and of course one of the primary food sources for Great whites are seals. So especially in that area. So, uh, in the size that these uh, that these sharks get they need Larger prey that a lot of fat on the prey. So that's why they tend to like Um, they like seals So overall this study really saw that there was a difference that there was this strong seasonal trend Summertime they were up in the northeast United States Wintertime they were down in the southeast United States And then of course there were outliers or or variations along that but mostly focusing on those two areas Um, there was a lot of different prey They they they focus on different prey habitats. That's where the primary reason why they were in those areas Was suggested by the study and then of course secondary is the temperature They needed to be within a specific temperature range and it tended to be 14 to 23 degrees celsius So I found that that interesting and One of the things that I also found interesting in this study and and it's you know It's always interesting to to hear these studies because they're very scientific They have to be very critical of of their methods They have to make sure that they let the reader know especially other scientists that these are their methods This is the way they they gathered the data and that there are restrictions And one of the restrictions that they've mentioned was that this is fishery observed data So anything that has to do with fisheries so gill nets Longlining and rod and reel were tend to be the most interactions that they had with with great whites And this means that it doesn't necessarily mean that other observations didn't occur But most of these observations were fixed where fishing boats were Uh, so that could limit the data in terms of other places where these sharks actually go So there might be a little more variability in terms of where Um, these these fish are actually found because i'm sure Fishery boats will actually be in specific areas to capture, you know, other fish Large larger fish or smaller fish or whatever they're trying to to find Um, but that's one of the limitations that they found So they said well, maybe other data like satellite tag data that we see now Can shed a little more light in terms of variability or where they're going on a you know on a bit more specific route Um, which they have been able to find with satellite tags by Other researchers and companies and organizations like ocean arch and and whatnot So we're kind of seeing, you know different data sets Basically tell the same thing there has been other research or other data sets that have found like through satellite tag and have found a strong seasonal Um, um, uh, sort of seasonal trend of summer in the north and with us, um Summer in the north and winter in the south so That I find this is kind of just solidifying that The other thing they talked about was, uh, the overall trends so what's happening with the great northwest Atlantic great white sharks What is the status and normally people are saying that the that the status has been going downhill for a long time And this study found that in the 70s and 80s that was true There was definitely a downward trend in the abundance of great white sharks based on fishery of observations Uh, which is what this, you know, what the data said that I just talked about Before the 70s and 80s the the trend descend tended to be the same But it wasn't going down it was stabilized and maybe even growing a little bit In the 1990s when shark protections were actually put into place and implemented Uh, in this area, they noticed that there was an increase or that no not necessarily that there was an increase but that the population stabilized and that there was a bit of an increase Uh, in the sightings of these species and they usually measure it like, um Uh, catch per unit effort CPUE Okay, so it's catch per unit effort and so it's the amount of times it takes to catch a great white shark And so the shark before the 1970s was represented as one out of every 3704 sharks captured in this fishery was a great white shark After which after the 1990s when this this was implemented Uh, one out of every 3,443 sharks captured Uh, in the same area between 1994 and 2003 were great white sharks So a rock a remarkably small difference in that ratio Uh, which means that this the species has kind of recovered from the 70s and 80s down great Now of course, I'm going to go out on a limb here and say that 70s and 80s is when jaws came out And of course jaws was uh, I believe was The whole movie setting was on the east coast Um, so that may have played a bit of a role I can't say for sure, but a bit of a role into maybe that downward trend People were actually killing them more than they were actually, um, you know admiring them However, you know, that's just my that's just my pain. That's not the paper's opinion But what was good is to see that the species the population has bounced back a little And what the the observations of the of the study knows that from other studies that populations in New Zealand California, uh, and south africa noticed the same Sort of trends where in the 2000s and 1990s and 2000s when other protections were implemented In those countries they noticed that or in those areas they noticed that the populations have stabilized and gone out So that's a good news overall Showing that the populations have stabilized and are starting to increase a little bit from what was happening in the 1780s So I thought this research paper is really well done I like the fact that they they showed they had a whole couple paragraphs on their limitations of their data Just because they were fisheries observed data But it was it is a big data set and for species that we don't know a lot about when we haven't been studying It's great to see that they put studies like this together to Essentially create a baseline of what's been happening. What are the trends over a 210 year period, especially in the last say You know 70 years or so so that that's really kind of need to see that it went from you know stabilize Maybe growing a little bit down and then back to stabilizing and growing a little bit Um, so it's great to see but of course efforts And still need to be done to make sure that these populations are still stable and making sure that they're growing So we get more of this apex predator around to do what it does best and that's essentially regulate populations of its prey and So it's good to see that we see protections. They still need to be enforced. It's they're not perfect And they still need to be improved in different ways in different areas However, all those are unique to those areas and what's been happening fishery pressures Climate change can change their distribution pattern You might see more of a shift northward of this species because of higher sea surface temperatures that are hitting Northern more northern areas in in the ocean, so we might see a little bit of a shift in that Range because three to 28 degrees is a pretty big range and even 14 to 23 degrees if that shifts up a bit You might see more in Canada um and less in say Florida in the future if that if those trends continue So it's always good to know these kind of things about a species, especially something a species as important as the great white shark So I want to thank the authors for producing this. This was done in 2014 So really appreciate the updated versions and what we'll do is we'll put the link to the article on this On the show notes, which is speak up for blue.com Ford slash session Actually, sorry. This is session 89 my apologies. I've been saying Um, oh, sorry 90. This is session 90 because it is there's a pre-record these. This is session 90 So I apologize for the mistake But yes, uh, it is session 90 and so it'll be speak up for blue.com for slash session 90 And we will have that The the paper up for you so you can see the figures and all the the different data for you So thank you very much for listening and also I want to say if you want to support the podcast You can go to our patreon crowdfund site that speak up for blue.com For slash patreon P A T R E O N and you can help support this podcast help support My efforts and my team's efforts to continue to provide you with ocean conservation information such as this by Supporting our crowd funding campaign. I really appreciate if you do it really furthers our reach and our efforts Into providing more ocean conservation information out on the internet sphere So thank you very much. I really appreciate you've been listening speak up to the podcast. I am your host Andrew lewin happy Research thursdays and conservation [Music]