Scientists studying seals' impact on steelhead

We already know that seals eat adult salmon and steelhead - ask any fisherman. But scientists need to know if seals eat the small, young salmon that are disappearing in Puget Sound. KING 5 Environmental Specialist Gary Chittim shows how biologists are wiring up fish and seals in a high tech search for answers. .... http://www.king5.com/news/Scientists-studying-seals-impact-on-steelhead-270559521.html

Good to see that piece of the puzzle being explored.

The testimony at the recent senate hearing is that there are 30,000 harbor seals between Puget Sound and Vancouver Island. That is an unbelievable gauntlet the fish swim through when entering Puget Sound from the rivers and then leaving to and returning from the ocean.

I know that guantlet has taken caught salmon off my hook on occasion.

LL-
If I recall correctly the number of harbor seal in Washington waters have increased from less than 4,000 in the mid- 1970s to more than 32,000 today.

Curt

At any rate the numbers of pinnipeds is way the sustainable number set by NOAA for the Sound many year back.

With the pinnipeds eating 8X more now, than the 1970's, ---it wouldn’t surprise me if smoults are flipper lick’n good.

8x the predators would probably make a big difference. I'm usually reluctant to point to predation as a leading cause of salmonid declines, but it's hard to dismiss an eightfold increase in predators relative to a time when the fish were much more abundant. Shouldn't we assume that such a dramatic increase in predators would have similar effects on the salmon populations?

It will be interesting to see what this turns up. Either way, 30,000 pinnipeds seems pretty far out of balance....

Many herring stocks have under gone critical declines, and there is concern that pinniped predation may have increased the natural mortality rate of herring in some areas (Musick et al., 2000), although it is acknowledged that there are likely many factors that contributed to the decline of herring (Stoutet al., 2001). Spawner biomass of herring for the northern Puget Sound, an index of population abundance, remained low through the study period, yet herring has been identified as one of the top prey species of harbor seals in a San Juan Islands diet study since 2005 (Lance et al., 2012).

Like herring populations, salmonid populations have undergone serious declines, and there is also concern that pinnipeds may affect salmonid recovery (NMFS, 1997; Wright et al., 2007).

The issue of seal predation came up during the legislative hearing on the State Auditors Office (SAO) performance audit of the WDFW Blackmouth program a few years back. Lots of stats about significant reductions in the contribution rate by hatchery releases driving up the cost of each such fish harvested. Culprit? Seals do eat salmon.

Then came the P.S. Rockfish Recovery plan and hearings. In that draft plan citing limitations on recovery there was a section of food chain factors. In that section seal predation was cited and rated as minimal based upon there being approx 15 thousand seals in Puget Sound (inland waters) consuming 5 million pounds of food (fish) calculated by WDFW based upon cited average seal weight and daily consumption needs per pound of body weight. That 5MM pounds was a bogus number as a quick series of calculator inputs yielded a number of 27MM pounds. And seals DO eat rockfish! I think it was that same Lane study cited by Lucky Louie which described scat studies and yielded a percentage with rockfish DNA. Oh, and the WDFW personnel pushing that program, having been advised of their significant error, continued to utilize it throughout the rest of their public hearings.

The data I researched indicated that there were only a couple of hundred seals in P.S. in the early 70s as the result of a Dept. of Fisheries bounty program. Between that program going away and the MMPA the seal population grew exponentially to a number probably around 17M now.

So, bottom line, if one were to plot the decrease in blackmouth contribution rates and rockfish numbers over that same period you would see a clear inverse relationship. And seals do eat salmon as well as rockfish and if the total poundage for 17M seals is approx 30MM of food it doesn't take a very big percentage to equal a lot of blackmouth, rockfish and/or (gasp) steelhead.

The 30K number recently thrown around was for the Salish Sea to include inland Canadian waters and in WA the coastal seal population is counted separately from P.S. numbers.

There was a study published last year about QFASA used to determine the diet that contributed to the stored fat of sampled harbor seals.

My impression was that harbor seals like humans might have individual preferences on what they eat on the seafood menu but that isn’t to say if a convenient free meal showed up the seal wouldn’t hesitate to gobble it down.

Interestingly,” Rockfish were estimated to compose up to 50% of some individual seal diets. Although estimates of harbor seal diet composition varied spatially, demographically, and among individual seals, species of rockfish were estimated to compose a large proportion of the diets of several individual seals.”

The conclusion was “our findings confirmed the importance of salmon species and Pacific Herring in harbor seal diets, but they also revealed that other species, including rockfish species, may contribute more substantially to harbor seal diets than had been realized previously.”

Also, I was sort of surprised about the amount of dogfish that is in the seals diet.

I don’t know if it was unfortunate, insignificant, or intentional that steelhead weren’t mentioned in this paper but hopefully the experiments being done in the first post of this subject-topic by Phoenix 77 will shed some light.

The question shouldn't be if the seals are eating steelhead but the question should be how many.

During the PSRRP hearings the WDFW "experts" were asked to quantify the numbers of the three ESA listed rockfish species consumed annually by harbor seals (leaving out California sea lions and Stellar sea lions). They didn't have any information although they were quick to suggest that the rockfish DNA in the seal scat was likely of the Puget Sound rockfish species due to its high population numbers.

My take was that they simply didn't want seals to be perceived as a significant factor in rockfish recovery because then they would have the dilemma of how to address that factor in a recovery plan. In short, the "Hear, See and Speak No Evil" approach.

Well, maybe the listing of P.S. Chinook and steelhead and this resulting study will shed some light on the impact of predators and, furthermore, be of some use when NOAA/NMFS begins its expected effort to develop a P.S. Rockfish plan.

Note how far the regulators are staying from providing fish for the Killer Whales to eat? Addressing harassment and silence on the fish.

The marine mammals don't have a choice. They eat fish. We have either ensure there are enough fish for them to eat of decide that we would rather do without the mammals and eat the fish ourselves.

I remember reading somewhere that the seals and sealions preferred lamprey to salmon, at least in rivers and estuaries. More fat, fewer bones, more of them. Maybe we should work harder on restoring the numbers of all the fish out there. Might actually leave more for us.

The problem with the Pacific Lamprey on the Columbia is that dams have done the same thing to them as they did to salmon...and I think we all know that dam operators/regulators on the Columbia would rather fuckaround for another 60 years with technofixes and pretend that dams are part of the natural environment.

Fish on...

Todd

The quantitative fatty acid signature analysis (QFASA) study alluded to earlier has 19 prey classes defined for 269 fish signatures.

The study doesn’t reveal if steelhead was one of the 269 fish signatures put into one of the prey classes. However, one would imagine that steelhead was one of the 269 and impacts on steelhead by harbor seals are probably already known.