Study Suggests Diet Of Great Lakes Salmon Has Changed

[AwolRJ]

Study suggests diet of Great Lakes salmon has changed

http://www.outdoornews.com/February-2013/Study-suggests-diet-of-Great-Lakes-salmon-has-changed/

By Victor Skinner Contributing WriterBy Victor Skinner Contributing Writer

Posted on February 14, 2013

Charlevoix, Mich. — A study recently published in a scholarly journal highlights why officials reduced salmon stocking in Lake Michigan, as well as how the lake is mimicking trends seen in Lake Huron before the salmon crash occurred there.

Several U.S. Fish and Wildlife Service, U.S. Geological Survey, and Michigan DNR researchers authored a study of Lake Michigan salmon stomachs published by Transactions of the American Fisheries Society in January, comparing what the fish ate in 2009 and 2010 to their diet in 1994-96.

What they found was that salmon shifted from a more diverse diet of larger alewives, bloaters, and rainbow smelt to almost entirely alewives. The alewives they’re eating now are also smaller in general than in the past, according to USFWS researcher Greg Jacobs, who started the study as a grad student with the University of Michigan.

“The biggest thing is the larger alewives … just aren’t out there anymore,” Jacobs told Michigan Outdoor News. “Chinook like big alewives, but they’ve run out of alternatives so they are eating more and more alewives as time passes.”

Researchers collected more than 1,000 salmon stomachs from all states surrounding Lake Michigan in 2009 and 2010, and compared what they found to salmon diet analysis conducted by the DNR in the mid-1990s. Results showed diversity of the fish diets for small salmon (under about 20 inches) shifting from 58 percent alewives in the 1990s to 85 percent alewives in 2009-10. The diet of larger salmon went from 84 percent to 99 percent alewives.

Chinooks in Lake Michigan are not only eating a higher percentage of alewives, but those alewives are smaller on average and contain less nutrition than before, researchers said.

“Smelt are at extremely low levels and bloaters are at extremely low levels so there really isn’t any alternative prey for the salmon,” said Randy Claramunt, a DNR research biologist who helped conduct the study. “It’s bad news and it’s kind of discouraging to see the lack of diversity of prey (species) and big prey.”

Salmon stomach analysis also confirmed what researchers have found in bottom trawls in recent years – that there is a “truncation” or reduced range in the age and size of alewives in Lake Michigan.

Chuck Madenjian, a biologist with the U.S. Geological Survey who contributed to the salmon study, said both the less diverse salmon diet and the truncation of the size of alewives salmon are eating in Lake Michigan mimic trends witnessed in Lake Huron before the salmon population crashed around 2003.

“In Lake Huron they would routinely get 7-, 8-, or even 9-year-old alewives” in bottom trawls, Madenjian said. “That was pretty consistent until about the year 2000 … and then instead the highest age that were sampled were 5-year-olds.

“The highest age we caught in 2000 (in Lake Huron) was 5, and that pattern persisted into 2001 and 2002.”

The same thing is happening in Lake Michigan, only at a slower pace. It’s one of several indicators resource managers considered when they reduced salmon stocking in Lake Michigan to better balance prey fish and salmon populations, he said.

“In 2009 through 2011, the oldest alewives we’ve got were age 6. We used to get 7- and 8-year-olds,” Madenjian said. “And it looks like things aren’t improving, because in 2012 the oldest age we got in the bottom trawl was age 4.

“Things aren’t getting better, that’s for sure, if anything, they’re getting worse.”

[Dozer]

Smaller over all salmon sizes, smaller forage available... carrying capacity shift? Disaster looms ahead... I want to add that a shift in diet doesn`t always spell disaster either, the fish could have started eating smaller alewives because the trade off between energy use vs. gain from hunting down larger alewives forces the fish to eat the smaller ones... however the decline in older, larger alewives is alarming. Problems like these aren`t fixed over night either... takes years...

[The_Fish_Dawg]

2012 New York Lake Ontario Fisheries Program Hilights

http://www.dec.ny.gov/docs/fish_marine_pdf/lou2012hilights.pdf

[ron4blues]

Correct me if I'm wrong but the stocking of Pacific Salmon species in the Great Lakes was originally intended as a measure to control alewive (also a non-native specie) numbers. This news might be bad news for anglers and industries that have come to rely on salmon populations in the Great Lakes, but it signals success with respect to the original intent. Here's a couple articles on the subject:

http://www.tandfonline.com/doi/abs/10.1080/03632415.2012.731875?journalCode=ufsh20

http://www.glfc.org/eforum/article3.html

[ron4blues]

Another thing not widely known is that alewives are edible. On the East Coast they are most commonly known as gaspereau and when they run into freshwater streams to spawn, many people flock to harvest them. They are in fact quite tasty.

http://en.wikipedia.org/wiki/Alewife

[scapulataf]

Interesting read. I guess the salmon have just eaten all of the big alewives that are out there and thus have to go for the smaller ones. One less invasive species to worry about. Well, not quite, but an invasive species on the decline it would seem..

Smallmouths have taken a liking to Gobies. Hopefully big Muskie and Pike will take a liking to the Asian Carp when they inevitably find their way in to the great lakes.

[AwolRJ]

They are saying this is what happened on Huron right before the Salmon crashed. They aren't catching older alewives any more just 4-5 yr old ones in the test.

[jordanl]

Interesting read. I guess the salmon have just eaten all of the big alewives that are out there and thus have to go for the smaller ones. One less invasive species to worry about. Well, not quite, but an invasive species on the decline it would seem..

Smallmouths have taken a liking to Gobies. Hopefully big Muskie and Pike will take a liking to the Asian Carp when they inevitably find their way in to the great lakes.

perch too, perch eat quite abit of them, seems like alot of the predatory fish are consuming gobies i know if gotten quite a few fish on goby style baits. but they are a hard species to control it seems

[arkangel06]

Maybe the salmon with switch to the gobie.

[steve-hamilton]

browns might. but salmon don't live where gobies live.

[blairwelsh]

Correct me if I'm wrong but the stocking of Pacific Salmon species in the Great Lakes was originally intended as a measure to control alewive (also a non-native specie) numbers. This news might be bad news for anglers and industries that have come to rely on salmon populations in the Great Lakes, but it signals success with respect to the original intent. Here's a couple articles on the subject:

http://www.tandfonline.com/doi/abs/10.1080/03632415.2012.731875?journalCode=ufsh20

http://www.glfc.org/eforum/article3.html

OMG .... I spit my Coffee out laughing!

THANK YOU

You are 100% Correct

What makes me laugh ... is that I am NOT a KNOW IT ALL, however when you've been around LONG ENOUGH and READ and SEE all the efforts / interference / different views on Conservationism, Invasive vs. Non- Invasives

Just seems like there are SO MANY differences of thought.

Half the people out there no longer even know what a "Real Invasive" vs. Introduced species is.

Doesn't matter in my opinion, if they are THERE (Here) then that's about it.

Nature will work something out.

We may not "Like it".... but guess what: IT IS WHAT IT IS.

[Dozer]

Regardless of whatever reason salmon were stocked, the focus, from what I beleve is to keep and maintain the fishery we currently have, for reason other than controlling alewife populations... I think...

Nature will take its course no doubt, we need to intervene in order to keep that salmon fishery going. To maintain those salmon pop. where they are now we should start stocking alewives... predator populations are up and demanding, prey populations are dwindling and getting smaller... predator pop. will crash... prey populations should rise, therefore predators will rise and up and down she goes, hopefully neither go extinct... and finally, asian carp. Wasn`t there a thread a year ago on here about Michigan cutting the stocking by half... saying they don`t need to stock more because of the number of wild salmon returning... or is it that they screwed up and overstocked.

I have a feeling this will play out in Lake Ontario as well... with the constant increase of predators over the last few years, a threshold will be breached in the future... I hope I`m wrong... however in Fish Dawgs` post from the DEC they state this is the first year they`re stocking ``bloaters``, something may be already brewing...

EDIT : We see the issues one the top of the food chain, salmon and alewives decreasing... however the problem may also exist on lower levels of the food chain as well...

[fishnhunt]

An overlooked problem with many of our native fish species now consuming Gobies is a bioaccumulation of toxins throughout the foodchain. A large portion of the Gobies diet consists of Zebra mussels (another invasive) which are responsible for filtering out many of the toxins in our Great Lakes. These toxins are then passed on to the Gobies, then passed on to the fish that eat the Gobies, and eventually passed on to us who consume the fish.

[kevin]

Correct me if I'm wrong but the stocking of Pacific Salmon species in the Great Lakes was originally intended as a measure to control alewive (also a non-native specie) numbers. This news might be bad news for anglers and industries that have come to rely on salmon populations in the Great Lakes, but it signals success with respect to the original intent. Here's a couple articles on the subject:

http://www.tandfonline.com/doi/abs/10.1080/03632415.2012.731875?journalCode=ufsh20

http://www.glfc.org/eforum/article3.html

You hit it right on the head. The salmon fishery now is strictly a $$ thing, as the fishing generates big money. The original intent was to drop the numbers of baitfish down. They need to decide now if they are going to allow the lakes to return to their natural, original state, or artificially maintain the salmon fishery for sportfishing and revenue.