Pinniped Predation - Houston we have a problem

searun

Well-Known Member
Pinniped populations in the Salish Sea and elsewhere have increased beyond historic levels. Chinook and Steelhead populations have steeply declined in a similar pattern. Hmmm, perhaps one of the stronger contributors to "poor ocean" survival is being uncovered by recent research.

A small clip from research currently underway to augment similar findings in a number of studies underway on both sides of the Canada/US border. Both efforts finding the same result - that pinnipeds are a more significant source of Chinook mortalities than previously thought.

Moreover, we are starting to see harbour seals in particular venturing up into rivers in pursuit of smolts and adults alike.

The Salish Sea Project is starting to uncover a wide variety of causal factors. Everything from predation to over-fishing of the critters in the food chain that help juvenile salmonids thrive (crab larvae, herring, krill).

If we truly want to see Southern Resident Killer Whales (SRKW's) rebound, the answer may rest with a well rounded and disciplined recovery effort that includes increasing smolt production, increasing food sources available to juvenile salmonids, and most importantly significantly reducing pinniped predation.

Check out this research article, and in fact please take the time to read the other research contained on the Salish Sea Project site....this is profoundly enlightening as to the complex issues facing chinook recovery.

https://marinesurvivalproject.com/research_activity/list/predation/

Here's a clip from the paper as a sample - note the significant estimates of chinook/coho mortalities directly attributable to pinniped predation!!!

This team assessed the impact of seals on salmonids in Cowichan Bay by counting the number of predators in the Cowichan Bay, quantifying predation events from visual observations, and determining diets from morphological and genetic analysis of fecal samples. Data collected for 2012-2014 provides the following estimates of the percentage of chinook and coho juveniles lost to seal predation in the Strait of Georgia:

-Chinook: Mean = 40% (95% CI: 32-45%)

-Coho: Mean = 47% (95% CI: 44-52%)

These data have been used in a model developed by PhD student Ben Nelson to test whether pinnipeds are inhibiting the recovery of commercially and recreationally important stocks of Chinook and coho salmon in the Strait of Georgia. Given these estimates, it appears that harbour seal predation is likely responsible for a significant amount of natural mortality in the early marine stage for both Chinook and coho salmon in the SOG. Ben notes that seal predation appears to be highest on juvenile fish between 115-145mm in length, but also cautioned that the consumption estimates and mortality could be biased due to high emphasis on “estuary seals” because of the locations that scats were sampled.
 
Pretty much what the old timers over here in Port Angeles have been saying for the last thirty years. And they didn't have to sample any scat to figure it out.
 
Good luck getting the bleeding hearts to agree to a cull. They will wait till all the herring is gone then the salmon then the whales will starve even more.
 
Have witnessed large herds of seals “rushing” as a group in the Big Qualicum when the fry are coming out in May and June and will confirm that in significant numbers the seals are targeting fry. Curious to know if this is more evident in hatchery rivers. I grew up here and the large seal populations were not here in the 60’s and 70’s when salmon stocks were really healthy in the Gulf of Georgia.
 
There is already a thread that discussed some of the Seal research at length Salish sea seals eat 86% of smolts.
To be clear its not a cull. it would have to be a kill, that occurs over and over again as the seal population will increase again as the food sources supporting their population are still there. Its not like the east coast where the seals are killed on remote ice flows and the carcasses hauled away. The killing here would be close to populated centers, with TV cameras showing the carnage, and bloated smelly seal carcasses washing up on local beaches. Its also interesting you bring up the Cowichan, as the latest DFO assessment of Chinook stocks identified one bright spot, ECVI stocks were classified as "rebuilding" , and the Cowichan particularly has had strong increasing Chinook runs, that in the last couple of years have surpassed escapement targets. Meanwhile WCVI stocks that were identified in other research (https://www.nature.com/articles/s41598-017-14984-8.pdf) as having low seal predation issues have not done well. The research also indicates that total seal consumption of smolts is much less than the increase in smolt production from hatcheries, so Chinook stocks have continued to decline in the Fraser, Southern mainland, WCVI and Northern BC despite large increases in net smolt production.

I grew up here and the large seal populations were not here in the 60’s and 70’s when salmon stocks were really healthy in the Gulf of Georgia.

There is a correlation with seals, and lots of other correlations, but correlation and causation are two different things. Other correlations with declining salmon stocks since the 1970s include:
1. Significant overfishing of stocks right through the 70s into the early 80s
2. Commercial extinction of many runs of herring due to roe fisheries in the SOG that are only now just beginning to recover
3. Massive increases in Hatchery smolt production via the smolt factories constructed through the SEP program
4. Warming waters in the Pacific and particularly the SOG
5. The appearance and proliferation of open net pen Atlantic salmon farms
6. Industrial scale logging of watersheds, with new logging techniques allowing clear cut logging of ever steeper slopes
7. Just prior to the collapses the building of Dams throughout the province
8. Changes in water chemistry (acidification) of lakes and rivers

So is it the seals (they are an easy scapegoat) or one of the other factors? Just as we were depleting the herring stocks in the SOG, likely an important food source, we began to flood estuaries with millions of nice, fat, predator naive, tank raised smolts in many estuaries. Hatchery smolts survive at much lower rates than naturally spawned ones. Predators will take advantage of the opportunities they are afforded, and its not only seals, but research has identified mergansers, gulls, herrons, and on the Cowichan there was even a family of Racoons that chowed down on large numbers of hatchery smolts. Should all those species that also gorge on the hatchery bounty be killed? The evidence is far from clear that seals are THE reason for salmon declines, its almost certainly a multifactorial issue, and unravelling which are responsible for what proportion of the declines is probably impossible. One thing is certain - Its us that's at the heart of the issues the salmon are having.
 
There is already a thread that discussed some of the Seal research at length Salish sea seals eat 86% of smolts.
To be clear its not a cull. it would have to be a kill, that occurs over and over again as the seal population will increase again as the food sources supporting their population are still there. Its not like the east coast where the seals are killed on remote ice flows and the carcasses hauled away. The killing here would be close to populated centers, with TV cameras showing the carnage, and bloated smelly seal carcasses washing up on local beaches. Its also interesting you bring up the Cowichan, as the latest DFO assessment of Chinook stocks identified one bright spot, ECVI stocks were classified as "rebuilding" , and the Cowichan particularly has had strong increasing Chinook runs, that in the last couple of years have surpassed escapement targets. Meanwhile WCVI stocks that were identified in other research (https://www.nature.com/articles/s41598-017-14984-8.pdf) as having low seal predation issues have not done well. The research also indicates that total seal consumption of smolts is much less than the increase in smolt production from hatcheries, so Chinook stocks have continued to decline in the Fraser, Southern mainland, WCVI and Northern BC despite large increases in net smolt production.



There is a correlation with seals, and lots of other correlations, but correlation and causation are two different things. Other correlations with declining salmon stocks since the 1970s include:
1. Significant overfishing of stocks right through the 70s into the early 80s
2. Commercial extinction of many runs of herring due to roe fisheries in the SOG that are only now just beginning to recover
3. Massive increases in Hatchery smolt production via the smolt factories constructed through the SEP program
4. Warming waters in the Pacific and particularly the SOG
5. The appearance and proliferation of open net pen Atlantic salmon farms
6. Industrial scale logging of watersheds, with new logging techniques allowing clear cut logging of ever steeper slopes
7. Just prior to the collapses the building of Dams throughout the province
8. Changes in water chemistry (acidification) of lakes and rivers

So is it the seals (they are an easy scapegoat) or one of the other factors? Just as we were depleting the herring stocks in the SOG, likely an important food source, we began to flood estuaries with millions of nice, fat, predator naive, tank raised smolts in many estuaries. Hatchery smolts survive at much lower rates than naturally spawned ones. Predators will take advantage of the opportunities they are afforded, and its not only seals, but research has identified mergansers, gulls, herrons, and on the Cowichan there was even a family of Racoons that chowed down on large numbers of hatchery smolts. Should all those species that also gorge on the hatchery bounty be killed? The evidence is far from clear that seals are THE reason for salmon declines, its almost certainly a multifactorial issue, and unravelling which are responsible for what proportion of the declines is probably impossible. One thing is certain - Its us that's at the heart of the issues the salmon are having.



We had seal hunting here decades ago. We stopped as the populations became low and liberal mindsets ruled. Just bring it back. We cant be so superficial, sometimes humans need to help set equilibrium again.
 
In the late 90's there was a experimental seal control program at the bottom of the Puntledge River . The seal barrier didnt work--but surprise !!! Shooting them did ! Have a read....... ABSTRACT Brown, T. G., B. Munro, C. Beggs, E. Lochbaum, and P. Winchell. 2003. Courtenay River seal fence. Can. Tech. Rep. Fish. Aquat. Sci. 2459: 55 p.
Various methods were employed to reduce harbour seal predation upon declining salmon stocks in the Puntledge and Courtenay Rivers, Vancouver Island, British Columbia. A seal barrier fence was operated at the mouth of the Courtenay River from June to September 1998. It was hoped that pre-spawning chinook salmon after passing through the fence would be safe from harbour seal predation. The seal fence did limit upstream movement of seals from midJune to August, but its effectiveness in reducing the number of salmon killed was questionable. The seal fence delayed salmon migration and seals were able to prey upon salmon holding below the fence. An acoustic deterrent device at the seal fence did not deter seal activity. A series of triads (cement interlocking columns) were placed along one side of the river downstream of the seal fence to provide refuge for adult salmon. The triads proved ineffective as adult salmon refuge.
Lethal removal of seals did not appear to reduce seal numbers at the fence for an appreciable period of time. Thirty-one seals were shot in 1997 and twenty-one more seals were removed in 1998 during the period of fence operation. We speculated that the influx of estuarine seals, attracted to the large numbers of returning pink salmon, maintained the number of seals in the lower river. The amount which the seal cull reduced predation on salmon is a difficult question that is not addressed in this report. However, in 2001-02 chinook returns to the Puntledge River increased substantially more than returns to neighboring rivers. The removal of habituated in-river seals and the corresponding reduction in both juvenile and adult salmon predation could have been one of many possible factors contributing to the increase in chinook returns. In 1998, observers monitored seal and salmon behaviours for 24 hours/day from midJune to mid-September. Assuming half of the total predation occurred in our observation area and assuming half of all the possible and probable kills were actual kills, seals killed 144 (38%) summer chinook, 700 (6.5%) pink, and 154 (33%) autumn chinook. Seal abundance corresponded to salmon abundance. Seal numbers were positively correlated to tide height (P < .0001), and seal numbers were significantly greater (P < .01) during flood tides. The number of seals varied diurnally, twice as many seals were counted at night and rate of salmon killed was 2 to 3 times higher at night than during the day. A significantly higher ratio of misses to kills occurred during the day (P < .01) which indicates that night pursuit was likely to be more successful then day pursuit. The distribution of salmon kills below the seal fence was different during day and night. More kills were recorded further down the river during the day (P < .001) and more kills were recorded during the day on one side of the river (P < .01). These differences in diurnal distribution of salmon kills may indicate either difficulties in our ability to observe foraging seals at night compared to day, or seal wariness.
 
Not to side track the thread, but seal predation is not the only answer to Chinook decline. What is necessary is a well researched and coordinated series of responses. We should start with the more obvious contributors to chinook mortality when determining how to prioritize the efforts. There are no easy solutions, it will come down to increasing chinook survival through reduced predation, increasing food sources for juveniles, impacts of pollution, etc.

However, when we are seeing seals many miles up rivers chasing salmon and steelhead adults and smolts it is clear they are getting desperate for food. We have been struggling to solve the mystery of what was leading to poor ocean survival. This research is starting to provide answers, and those numbers are shocking. Denying there isn't a cause and effect relationship of some magnitude is something I have difficulty comprehending.
 
In the late 90's there was a experimental seal control program at the bottom of the Puntledge River . The seal barrier didnt work--but surprise !!! Shooting them did ! Have a read....... ABSTRACT Brown, T. G., B. Munro, C. Beggs, E. Lochbaum, and P. Winchell. 2003. Courtenay River seal fence. Can. Tech. Rep. Fish. Aquat. Sci. 2459: 55 p.
Various methods were employed to reduce harbour seal predation upon declining salmon stocks in the Puntledge and Courtenay Rivers, Vancouver Island, British Columbia. .

Very interesting research. Probably the best source of recent BC data on a seal control program and the possible benefits. Too bad there wasn't a continuing study to see what the long term affect of the program would have been as there was an apparent correlation between seals and salmon abundance.
 
Pat, it was judged to be only partially effective as other seals just moved up into the river over time. But it was still effective in giving a threatened run of fish a break so that a good number could spawn.
 
What I and many others here in Port Angeles have witnessed in the harbor here is pretty hard to argue, thirty years ago there were rock fish and giant schools of squid and bait fish everywhere. They have suffered the same as the salmon shortly after the seal population exploded from a couple dozen to a couple hundred. When the salmon aren't around the seals just hammer the rock fish, squid and bait fish. Like any predator, They need to be managed.
 
Is everyone just going to hold hands and hope something is going to get done about seals as usual? It occurs to me that most fisherman hunt in the off season. If you enjoy your fishing, then do something about it.
 
A large scale kill is never going to fly politically and it is questionable in if it will have an effect scientifically. However, what may be able to be sold is a program like that on the Columbia river where specific problem animals that are keying on returning chinook adults, particularly at man made or caused barriers to natural fish movement, are removed from the river and either euthanized or placed in aquariums. Since 2008 when the program started there have been about 175 animals removed from the area at the entrance to the fish ladder at Bonneville dam, most of which were euthanized, a few such this one were relocated to aquariums.
https://www.opb.org/news/article/sea-lion-columbia-river-kill-salmon-aquarium/
While there is still likely to be opposition, as there is from some organizations on the Columbia River, it seems a balanced approach that doesn't involve indiscriminate slaughter with no guarantee of success, and can target the program to specific rivers and situations, and may avoid the inevitable backlash a knee-jerk slaughter of a native species feeding on its natural prey will have.
 
Whales are cuter than seals.

Once the impact that the seals are having on the Orcas becomes baked in to the general populace, the bleeding hearts will agree to a cull. Or maybe not agree, but look the other way and not be as 'outraged' or 'offended'. It will last a news cycle, and they move on to lynch someone who didn't use the right gender pronoun.
 
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