Seals Threaten Orca [and Chinook] Survival
- Thread starter Pursuit
- Start date
Pursuit
Active Member
Hi there ~ I've started to do a fair bit of reading on the impact of seals on Chinook and other salmon populations and thought I'd start to share some of what I've learned. My guess is this will be contentious but I'd appreciate comments on how to improve this kind of communication. All facts have sources but it is difficult to put them into a digital poster. Ultimately I'd like to get some of Coalitions/Foundations/Commissions on side with the idea of a seal/sea lion cull and any thoughts in that direction would be appreciated.
I've made up another 5 of these with different "factoids" which I can post if there is enough interest.
[Also this shot is lifted from the internet - it was taken by a Patrick Moody and I've not been able to find him on Fickr or Google to ask his permission to use it. If anyone knows him I'd appreciate getting his co-ordinates to get his permission]
I've made up another 5 of these with different "factoids" which I can post if there is enough interest.
[Also this shot is lifted from the internet - it was taken by a Patrick Moody and I've not been able to find him on Fickr or Google to ask his permission to use it. If anyone knows him I'd appreciate getting his co-ordinates to get his permission]
IronNoggin
Well-Known Member
Do you mind if I steal that image??
The way it is I mean...
Wondering...
Nog
The way it is I mean...
Wondering...
Nog
GLG
Well-Known Member
Can you post your sources for comment before you go too far?
Harbour seals target juvenile salmon of conservation concern. 2016. Austen C. Thomas, Benjamin W. Nelson, Monique M. Lance, Bruce E. Deagle, Andrew W. Trites. Can. J. Fish. Aquat. Sci. Can. J. Fish. Aquat. Sci.: 10.1139/cjfas-2015-0558
http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2015-0558
Abstract
Knowing the species and life stages of prey that predators consume is important for understanding the impacts that predation may have on prey populations, but traditional methods for determining diets often cannot provide sufficient detail. We combined data from two methods of scat analysis (DNA metabarcoding and morphological prey ID) to quantify the species and life stages of salmon (Oncorhynchus spp.) consumed by harbour seals in the Strait of Georgia, Canada, where juvenile Chinook and coho salmon survival is poor. Harbour seals primarily consumed adult salmon of lesser conservation concern in the fall (Aug-Nov): chum (18.4%), pink (12.6%), sockeye (7.4%), Chinook (7.1%), and coho (1.8%). However, the opposite species trend occurred during the spring when seals preferred juvenile salmon of greater conservation concern (Apr-Jul): coho (2.9%), Chinook (2.9%), sockeye (2.5 %), pink (1.4%), and chum (0.8%) ― percentages that can equate to many individuals consumed. Our data suggest that harbour seals select juveniles of salmon species that out-migrate at ages > 1 y, and provide evidence of a potential causal relationship between harbour seal predation and juvenile salmon survival trends.
http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2015-0558
Abstract
Knowing the species and life stages of prey that predators consume is important for understanding the impacts that predation may have on prey populations, but traditional methods for determining diets often cannot provide sufficient detail. We combined data from two methods of scat analysis (DNA metabarcoding and morphological prey ID) to quantify the species and life stages of salmon (Oncorhynchus spp.) consumed by harbour seals in the Strait of Georgia, Canada, where juvenile Chinook and coho salmon survival is poor. Harbour seals primarily consumed adult salmon of lesser conservation concern in the fall (Aug-Nov): chum (18.4%), pink (12.6%), sockeye (7.4%), Chinook (7.1%), and coho (1.8%). However, the opposite species trend occurred during the spring when seals preferred juvenile salmon of greater conservation concern (Apr-Jul): coho (2.9%), Chinook (2.9%), sockeye (2.5 %), pink (1.4%), and chum (0.8%) ― percentages that can equate to many individuals consumed. Our data suggest that harbour seals select juveniles of salmon species that out-migrate at ages > 1 y, and provide evidence of a potential causal relationship between harbour seal predation and juvenile salmon survival trends.
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Estimates of Chinook salmon consumption in Washington State inland waters by four marine mammal predators from 1970 – 2015. 2017. Brandon Chasco, Isaac C. Kaplan, Austen Thomas, Alejandro Acevedo-Gutiérrez, Dawn Noren, Michael J. Ford, M. Bradley Hanson, Jonathan Scordino, Steve Jeffries, Scott Pearson, Kristin N. Marshall, Eric J. Ward. Can. J. Fish. Aquat. Sci.
Abstract
Conflicts can arise when the recovery of one protected species limits the recovery of another through competition or predation. The recovery of many marine mammal populations on the west coast of the United States (U.S.) has been viewed as a success; however, within Puget Sound in Washington State (U.S.) the increased abundance of three protected pinniped species may be adversely affecting the recovery of threatened Chinook salmon (Oncoryhnchus tshawytchsa) and endangered killer whales (Orcinus orca) within the region. Between 1970 and 2015, we estimate the annual biomass of Chinook salmon consumed by pinnipeds has increased from 68 to 625 metric tons. Converting juvenile Chinook salmon into adult equivalents, we found that by 2015 pinnipeds consumed double that of resident killer whales, and six times greater than the combined commercial and recreational catches. We demonstrate the importance of interspecific interactions when evaluating species recovery. As more protected species respond positively to recovery efforts, managers should attempt to evaluate trade-offs between these recovery efforts and the unintended ecosystem consequences of predation and competition on other protected species.
Abstract
Conflicts can arise when the recovery of one protected species limits the recovery of another through competition or predation. The recovery of many marine mammal populations on the west coast of the United States (U.S.) has been viewed as a success; however, within Puget Sound in Washington State (U.S.) the increased abundance of three protected pinniped species may be adversely affecting the recovery of threatened Chinook salmon (Oncoryhnchus tshawytchsa) and endangered killer whales (Orcinus orca) within the region. Between 1970 and 2015, we estimate the annual biomass of Chinook salmon consumed by pinnipeds has increased from 68 to 625 metric tons. Converting juvenile Chinook salmon into adult equivalents, we found that by 2015 pinnipeds consumed double that of resident killer whales, and six times greater than the combined commercial and recreational catches. We demonstrate the importance of interspecific interactions when evaluating species recovery. As more protected species respond positively to recovery efforts, managers should attempt to evaluate trade-offs between these recovery efforts and the unintended ecosystem consequences of predation and competition on other protected species.
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A century of Chinook salmon consumption by marine mammal predators in the Northeast Pacific Ocean. 2016. Jesse Adams, Isaac C. Kaplan, Brandon Chasco, Kristin N. Marshall, Alejandro Acevedo-Gutiérrez, Eric J. Ward. Ecological Informatics 34 (2016) 44–51
a b s t r a c t
As many marine mammal populations have increased following bans on their harvest, there has been a growing need to understand potential impacts of these population changes on coastal marine ecosystems. Quantifying consumption of prey species, such as fish, is particularly important when those same prey are also targeted by commercial fisheries. Estimating the impact of marine mammal predators on prey fish depends upon knowledge of marine mammal diet composition; scientific advances over the last century have improved understanding of diets but have also led to inconsistent methods that challenge attempts at synthesis and comparison. Metaanalysis techniques offer the opportunity to overcome such challenges, yet have not been widely applied to synthesize marine mammal diets over space and time. As a case study, we focus on synthesizing diet studies of Chinook (king) salmon (Oncorhynchus tshawytscha) by four species of marine mammal predators in the Northeast Pacific Ocean: Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), harbor seals (Phoca vitulina), and killer whales (Orcinus orca). We also highlight several simple meta-analyses for which these types of diet databases may be employed. Our assembled database consists of N330 records, spanning more than 100 years. Results indicate that the frequency of occurrence of Chinook salmon in killer whale studies is high (63%) relative to pinniped studies (b10%). They also suggest a strong increasing ability to discriminate Chinook salmon from other salmonids,which we attribute to switches in diet studies from lethal or observational sampling toward molecular methods (DNA, fatty acids). Our database and analysis code are published as supplementary material, which we hope will be useful for other researchers and will inspire more of these syntheses.
a b s t r a c t
As many marine mammal populations have increased following bans on their harvest, there has been a growing need to understand potential impacts of these population changes on coastal marine ecosystems. Quantifying consumption of prey species, such as fish, is particularly important when those same prey are also targeted by commercial fisheries. Estimating the impact of marine mammal predators on prey fish depends upon knowledge of marine mammal diet composition; scientific advances over the last century have improved understanding of diets but have also led to inconsistent methods that challenge attempts at synthesis and comparison. Metaanalysis techniques offer the opportunity to overcome such challenges, yet have not been widely applied to synthesize marine mammal diets over space and time. As a case study, we focus on synthesizing diet studies of Chinook (king) salmon (Oncorhynchus tshawytscha) by four species of marine mammal predators in the Northeast Pacific Ocean: Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), harbor seals (Phoca vitulina), and killer whales (Orcinus orca). We also highlight several simple meta-analyses for which these types of diet databases may be employed. Our assembled database consists of N330 records, spanning more than 100 years. Results indicate that the frequency of occurrence of Chinook salmon in killer whale studies is high (63%) relative to pinniped studies (b10%). They also suggest a strong increasing ability to discriminate Chinook salmon from other salmonids,which we attribute to switches in diet studies from lethal or observational sampling toward molecular methods (DNA, fatty acids). Our database and analysis code are published as supplementary material, which we hope will be useful for other researchers and will inspire more of these syntheses.
GLG
Well-Known Member
Thanks AA. here is a video from one of the authors of this paper. This video is a couple of years old but it stands up well. I would caution anyone that is looking at a cull as a solution to contact PSF or Austen Thomas for advice.
Pursuit
Active Member
Please, go for it!
Pursuit
Active Member
The source for this is research that was part of the Salish Sea Marine Survival Project funded by the Pacific Salmon Foundation.
“We discovered that from May to October, about 40-60% of total juvenile coho, and about 30-50% of juvenile Chinook could be lost to seal predation,” said UBC doctoral student Ben Nelson who was involved in the study. Quoted in fishfarming .com Published: 29/11/2016 at 9:32 am
The results of the study were published in the Canadian Journal of Fisheries and Aquatic Sciences in October 2016.
Abstracts from the study are posted above but the whole study is only available if you pay $30
GLG
Well-Known Member
The source for this is research that was part of the Salish Sea Marine Survival Project funded by the Pacific Salmon Foundation.
“We discovered that from May to October, about 40-60% of total juvenile coho, and about 30-50% of juvenile Chinook could be lost to seal predation,” said UBC doctoral student Ben Nelson who was involved in the study. Quoted in fishfarming .com Published: 29/11/2016 at 9:32 am
The results of the study were published in the Canadian Journal of Fisheries and Aquatic Sciences in October 2016.
Abstracts from the study are posted above but the whole study is only available if you pay $30
Here is the article that you are referring to.
http://www.fishfarmingexpert.com/news/study-highlights-impact-of-seals/
Study highlights impact of seals
The massive population of harbour seals in the Strait of Georgia is likely playing a big role in reducing the numbers of juvenile coho and Chinook salmon, according to the results of a new study undertaken by researchers from UBC.
Author: Laura Braden, PhD
In 1970, harbour seals became federally protected in Canada, with numbers increasing from 5,000 to 40,000 in only 38 years. At the same time, populations of Chinook and coho salmon experienced serious declines. Recent research efforts have helped to determine that the effects of seal predation may be significantly affecting populations of juvenile salmon.
As part of the Salish Sea Marine Survival Project (SSMSP), funded by the Pacific Salmon Foundation (PSF), Dr Austen Thomas used a high-tech seal “beanie” to measure exactly how many juvenile salmon were being consumed by seals, and also collected seal scats to look for salmon DNA.
The SSMSP is a $20 million joint initiative of the PSF and Seattle-based Long Live the Kings to determine causes for declines of coho, Chinook and steelhead in the Salish Sea. The research – conducted by the Marine Mammal Research Unit at University of British Columbia (UBC) under Dr Andrew Trites – involves using DNA techniques to identify prey in seal waste as well as the development of ‘seal beanies’.
The beanies, created by Drs Austin Thomas and Brian Battaile, allows for an exact measurement of when a seal eats a PIT-tagged salmon, and the DNA sequences show which species of salmon was eaten.
“We discovered that from May to October, about 40-60% of total juvenile coho, and about 30-50% of juvenile Chinook could be lost to seal predation,” said UBC doctoral student Ben Nelson.
“What’s interesting about this is that there are significantly more chum juveniles in the Strait, but the seals are targeting Chinook, coho and sockeye,” explained Thomas. “This is likely because they are larger than chum when they enter the salt water, so its more worthwhile for seals to target them.”
According to Thomas, simply removing the seals will not solve the problem.
“The key question is why seals are now targeting these juvenile salmon,” he says. “We suspect that juveniles in the Strait could be compromised due to pathogens, poor food supply or lack of refuge habitat, which in turn makes them more vulnerable to predation. So if you remove the seals, another predator may simply move in to fill that void.”
“Another questions that has come out of this,” says Nelson, “is whether the abundance of hatchery fish in the Strait is signalling seals to feed on juvenile salmon rather than other species.”
The team’s most recent results were published in the Canadian Journal of Fisheries and Aquatic Sciences last month, and suggest that harbour seals are preferentially eating juvenile salmon species that out-migrate at ages > 1 y, and furthermore, provide evidence of a potential causal relationship between harbour seal predation and juvenile salmon survival trends.
Pursuit
Active Member
Thanks GLG! Just an excellent presentation of how they planned to measure predation by species and by location. Pretty amazing science. And it led to the conclusion that about 40-60% of total juvenile coho, and about 30-50% of juvenile Chinook could be lost to seal predation.
Looks pretty clear that seals are a significant part of the problem to say the least.
I will try to get in touch Austen Thomas re the cull solution which he doesn't seem to much like.
Pursuit
Active Member
View media item 406
The source for this is the second study abstract posted by Agentaqua above. They later adjusted the consumption from 625 tons to 628 although the 3 tons doesn't seem overly relevant given the huge quantity involved
The source for this is the second study abstract posted by Agentaqua above. They later adjusted the consumption from 625 tons to 628 although the 3 tons doesn't seem overly relevant given the huge quantity involved
GLG
Well-Known Member
View media item 406
The source for this is the second study abstract posted by Agentaqua above. They later adjusted the consumption from 625 tons to 628 although the 3 tons doesn't seem overly relevant given the huge quantity involved
I was just reading that paper....
https://www.researchgate.net/public...four_marine_mammal_predators_from_1970_-_2015
I also remember hearing the results last year at a meeting I attended and it was said that not all harbour seals are the same as it seems that just a few of them go after the smolts. That was proved by the beanie hats and what we have seen in our rivers in the spring migration events. I'm by no means in the know on what steps are going to be taken to "harvest" these seals but there may be things going on that will help. Sometimes things like that are best not talked about on social media.
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Pursuit
Active Member
Just realized the previous poster had a typo! Yikes sorry about that Nog
GLG
Well-Known Member
Here is a good resource that explains how to reconcile the difference between the two studies.
http://marinesurvivalproject.com/research_activity/list/predation/
Not sure if a poster that calls for "Time to design mitigation strategies" is as catchy a phrase as cull but it may not offend others and still get the point across. It also leaves the door open for other solutions that may be more realistic.
http://marinesurvivalproject.com/research_activity/list/predation/
Not sure if a poster that calls for "Time to design mitigation strategies" is as catchy a phrase as cull but it may not offend others and still get the point across. It also leaves the door open for other solutions that may be more realistic.
chromatose007
Well-Known Member
This was in the Vancouver Sun. The MSM passed over it. Wonder why?
https://www.google.ca/url?sa=t&rct=...Ff42Zby2n67BHgmYCLtL5A&bvm=bv.146094739,d.cGc
https://www.google.ca/url?sa=t&rct=...Ff42Zby2n67BHgmYCLtL5A&bvm=bv.146094739,d.cGc
Lance, M.M., and S.J. Jeffries. 2006. Estimating importance of rockfish, lingcod and other bottomfish in the diet of harbor seals in the San Juan Islands. Contract Report to SeaDoc Society Research Agreement No.
K004431-22. Washington Department of Fish and Wildlife, Olympia WA. 20 pp.
http://dfw.wa.gov/publications/00428/wdfw00428.pdf
Lance, M.M., and S.J. Jeffries. 2009. Harbor seal diet in Hood Canal, South Puget Sound and the San Juan Island archipelago. Contract Report to Pacific States Marine Fisheries Commission for Job Code 497; NOAA Award No. NA05NMF4391151. Washington Department of Fish and Wildlife, Olympia WA. 30 pp.
http://wdfw.wa.gov/publications/01423/wdfw01423.pdf
K004431-22. Washington Department of Fish and Wildlife, Olympia WA. 20 pp.
http://dfw.wa.gov/publications/00428/wdfw00428.pdf
Lance, M.M., and S.J. Jeffries. 2009. Harbor seal diet in Hood Canal, South Puget Sound and the San Juan Island archipelago. Contract Report to Pacific States Marine Fisheries Commission for Job Code 497; NOAA Award No. NA05NMF4391151. Washington Department of Fish and Wildlife, Olympia WA. 30 pp.
http://wdfw.wa.gov/publications/01423/wdfw01423.pdf
Pursuit
Active Member
Thanks for the continuing comments and advice GLG.
No question that a call for a cull is emotionally charged and in the early innings it is more important to educate people and get them concerned about the problem than it is to push a particular solution. If folks buy into the problem solutions will be easier to sell. And as a result of reading the research papers noted above and learning about the work being done by Austen Thomas I recognize that it is complicated and that a variety of mitigation strategies may be appropriate. How about "It's time for population control measures" which leaves rooms for a range of solutions. It's a step back from "Cull" but less 'governmental' than mitigation. Here it is on another digital poster:
View media item 408
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