Fish food: Hungry salmon overwhelm Lake Ontario alewives

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New research shows there may be too many Chinook salmon in Lake Ontario for alewives - their prefered food - to overcome. Photo: GLERL

Too many Lake Ontario Chinook salmon threaten the survival of the alewives they eat. Photo: GLERL

(UPDATE: Michael Connerton, co-author of the research written about here, responded by email Monday to points he thought were omitted or exaggerated. Specific criticisms have been added in italics below. See more discussion of this article at Lake Ontario United.)

A biological balancing act between the premier Great Lakes sportfish and its prey could be at a tipping point in Lake Ontario.

Chinook salmon are the foundation of the Lake Ontario recreational fishery, which is worth $76 million to New York alone. But new research shows that the popular predators could be so abundant in the lake that there may not be enough alewives – the Chinook’s main prey fish – to go around.

If there aren’t enough alewives to both reproduce and feed the salmon, each species will collapse. That’s what happened over the past five years in Lake Huron, where alewives and the Chinook salmon fishery have all but disappeared.

“The alewife population could be at severe risk of collapse like what happened at Lake Huron,” said Brent Murry, a biology research assistant professor at Central Michigan University who did doctoral research on Lake Ontario. “We need to reevaluate the stocking plan.”

(Connerton: “Age-3 Chinook salmon in Lake Ontario average about 5 lbs heavier than salmon in Lake Michigan and are almost double the size of Lake Huron’s right now, so the lakes are really quite different and difficult to compare directly”)

Same story, different lake

In 2006, Lake Michigan managers fearing the same fate as Lake Huron cut back Chinook salmon stocking by 25 percent, hoping to make life easier for alewives. So far, that strategy has worked, said Randy Claramunt, research biologist with the Michigan Department of Natural Resources and Environment.

“Reducing stocking has contributed to a reduced number of Chinook salmon in Lake Michigan,” he said. “Likewise, we’ve seen a response in the increased survival of alewife.”

And the salmon that remain are bigger and healthier than they were a few years ago, he said.

A similar salmon stocking cut could ease the pressure on Lake Ontario alewives, Murry said. But such a move is unpopular with the lake’s recreational anglers.

Charter boat captains on Lake Ontario have already seen salmon catch-rates decline after stocking cuts in the mid-90s, said George Watkins, secretary of the Ontario Sportfishing Guides’ Association.

“Part of our livelihood is the number of fish that are available to us,” he said. “Are you going to do a charter if all you’re going to do is go around on a boat ride?”

(Connerton: “Contrary to Watkin’s story in Ontario, anglers in New York have experienced the highest catch rates of salmon over the past seven years according to results from our Fishing Boat Survey (PDF) conducted annually since 1985.”)

But there may be reason to believe that a stocking cut might not be so bad for anglers looking to hook a Chinook.

Wild fish surprise

The link between salmon stocking and catch rates is based on an old assumption that the only salmon in Lake Ontario are the fish that were planted in there, said Michael Connerton, a senior research biologist with the New York State Department of Environmental Conservation.

A 2009 study shows that’s probably not the case.

The study, co-authored by Connerton and Murry, found that the 2.3 million Chinook salmon planted by New York and Ontario annually produce less than half of the Chinook in Lake Ontario.  Most have never seen a hatchery; they were born wild in tributary streams like the Salmon River in north central New York.

“So the widely held belief that there was limited to no natural reproduction is just completely and absolutely wrong,” said Murry.

Around half of the Chinook in Lake Michigan are born wild, Claramunt said. That makes a cut in salmon stocking for the sake of alewives easier to swallow for the lake’s anglers.

In a new study, Connerton and Murry estimated Chinook salmon abundance in Lake Ontario in a way that accounted for natural production. By coupling that estimate with the rate at which the salmon eat alewives, they determined that “predation pressure on the Lake Ontario alewife population may be high enough to raise concerns about long-term stability of this predator–prey system,” according to an article in the January 2010 issue of Transactions of the American Fisheries Society.

(Connerton: “The research by Murry, me and others still leaves a lot of questions that we need answered to really understand what’s going on out there, and how predator-prey conditions in Lake Ontario relate to the Upper Lakes. Lake Ontario is a large and complex system, and our ability to control the outcome through stocking may be less than people think. Weather, new invasive species, natural reproduction, and many other variables factor into the equation in ways we really don’t completely understand yet.”)

Managers hold stocking levels steady

Lake Ontario managers still aren’t convinced that a new stocking plan is needed, Connerton said.

The best indicator of the balance between Chinook and alewives is the average size of full-grown salmon, he said. That average was recently near an all-time low, but has since rebounded and stabilized.

“I think what they’ve decided over the past ten years is there doesn’t seem to be enough to indicate a stocking change,” he said.

But it’s something that biologists and managers alike will have to keep an eye on.

“Could we push the alewife population to a point where there’s too few alewife to sustain the population and our Chinook size would drastically decline because there isn’t enough to eat? Yes, of course. I think it could happen,” he said. “Hopefully it won’t happen so quickly that we can’t make adjustments.”

18 thoughts on “Fish food: Hungry salmon overwhelm Lake Ontario alewives

  1. Humans polluted the lakes with too many nutrients, known as eutrophication. This caused an overgrowth of phytoplankton. Zooplankton eat phytoplankton and they too exploded. Small fish eat the zooplankton, and they too exploded. To combat this ecological imbalance, an apex predator population had to be reestablished. But the native trout and salmon couldn’t cope with the pollution, so we introduced pacific salmon, a non-native species. Of course they did wonderfully. If any of you have any science or ecological understanding, non-natives can also become invasive. Technically all of your sacred sport fish, your pacific salmon, are non-native invasives. It seems that all you care about is fishing, a silly sport. Yea, its a multi-million dollar industry but its hanging on by a thread. We created an artificial ecosystem that is not sustainable. Soon there will be no fish for any of you to catch. Oh and I hope you haven’t been eating them, they are loaded with mercury among other things.

  2. Pingback: The sea lamprey moves on to the Great Lakes SmackDown! finals | Great Lakes Echo

  3. is it legal to collect alewives with an underwater light on lake Ontario. And is it legal to fish with alewives while the light is being use

    David

  4. We have had alewife stocked in our states lakes that contain striped bass and i’ve noticed a significant decline in alewife numbers prompting a call to a marine biologist who told me alewife reproduction is quite cyclical. We also noticed a decrease in striped bass sizes and numbers. Could this pattern and condition be also applied to the Great Lakes situation? Should we be patient and adjust or is it imperative to intervene? Is it legal to use an under water light to attract zooplankton, then alwives, then preditors. Then catch the alwives and use them for bait while the light is still lit?

  5. Since they are intentionally increasing the alewives whether we like it or not the point seems moot. Alewives eat the same thing Asian carp do, (including native larval fish) for 4 months of salmon fishing (good or bad)we sacrifice 12 months of good fishing for native fish as alewives hog the zooplankton and eat the laval fish.
    Protecting the alewives makes lake michigan safe for all invasives and the asian carp. Perch and walleye also eat alewives and salmon are not required to control them. They just inmply only a salmon can. Salmon cannot feed where baby asian carp will be, so thier useless.
    I see full boat launches in Saginaw bay catch limits of walleyes i see empty boat launches in west michigan. Trying to control nature never works. The asian carp just came out of Door no. 3 and we will all pay dearly for it, all because of the alewife protection plan!

  6. Gobies will not replace alewife as salmon prey. Gobies are shallow water bottom dwellers. Both salmon and alewives are pelagic species living generally in the middle of the water column over deep water.

    Gobies have become the prey of walleye, bass, pike and to a certain extent some trout species.

  7. Gobies should fill the alewife decline or some other invasive species will appear from the ballast waters….

  8. the alewife population isn’t JUST affected by the salmon.. the managers need to learn to look at the CORMORANTS!!! they eat MORE alewife than salmon do, and their more responsible for the population crash than anything else… if you guys want to learn the truth about this stuff look at a great fishing forum called http://www.spoonpullers.com and if you truly care about salmon fishing do what you can to persuade politicians and the powers that be to oil the eggs of cormorants and to do a huge cull then you will see some of the best salmon fishing again!

  9. It is simple… Alewives are invasive to many lakes, but native to Long Island. Why would people introduce a Pacific salmon (possibly viewed as another invasive, the Atlantic salmon has shown a decrease)to control an invasive. I can’t wait to see what is stocked to control big headed carp!!!

  10. Frankly, the true stakeholders of the Lake Ontario fishery have grown weary of efforts to “wean” anglers off the greatest inland fishery in the world. If and when the Salmon in Ontario can drive the densely populated Alewives down enough to reduce their body weight for SEVERAL years in a row, then we will consider reducing stocking numbers. Of course, catch rates would sky rocket in those same seasons. If this ever does happen, other fisheries in the Great lakes have proven that no lasting damage,only benefits occur. Anytime the alewives are driven down, good year classes of yellow perch and walleye are hatched. The Salmon are often treated like the “Rodney Dangerfields” of the Great Lakes, when in actuality they have helped every desireable fishery over the years. We are blessed to have the Mighty Chinook thriving in Lake Ontario.

  11. Bill and Paul, you guys have both referred to the impacts of stocking changes to non-charter folks — the “off the pier” and “breakwall angler” contingent.

    When I’m looking to report angler opinions, my most efficient option is charter groups who have Associations with staff members and office phone numbers. But that obviously leaves out the crucial section of the population you’re bringing up.

    That’s partly a casualty of reporting on Lake Ontario from an office in Michigan. But it doesn’t have to be. If either of you (or anybody else) would like to help me flesh out the “small boat” or “shoreline” perspective in any fisheries stories we write in the future, email me at jeffgillies@gmail.com

  12. The article is very misleading and does not really tell the whole story. While salmon catch rates may have declined in the Province of Ontario, New York continues to have excellent catch rates for kings. In fact, probably due to pen rearing projects along the south shore of the lake, chinook salmon catch rates have enjoyed the best seven years ever – the last seven year of the lake creel census conducted by DEC. In addition, while there has been some natural reproduction, how much is completely speculative. Success is dependent upon consistent water flows in the tributaries like the Salmon River. A couple years ago, there was very little if any natural reproduction due to low water levels. It’s not consistent enough to rely upon. A study is currently underway to get a better handle on what’s happening out there. And it’s not just the charter guys that have invested heavily into the salmon fishing. What about the lakeshore communities that rely upon these fish – and the fishermen – all year long in the streams, off the piers and in the lake. Take away the salmon and lose one of the most important components to the fishery – economic impacts, resident and nonresident license sales, Federal excise tax dollars. Look at the big picture, not just one small portion of it. And why do you think some of these fisheries like perch have come back? The salmon keeping alewife numbers in check.

  13. In 1993 the MI DNR discontinued stocking coho salmon in L. Superior. Since then we have seen a precipitous decline in the sport fishery for coho, even tho they continue to reproduce in the wild. This reproduction is low and variable from year to year, and does not provide the spot fisheries that stocking did prior to 1993. About 100,000 chinook smolts continue to be stocked annually, but, they have not provided much of a fishery.

    The spot fisheries that existed prior to 1993 were large and accomodated the small boat angler as well as shore and breakwall anglers. Those spot fisheries are now only a small fraction in comparison to what they used to be. Recently the MI DNR increased the creel limit for lake trout in L. Superior from 3 to 5, supposedly to increase opportunities for anglers. Also,I’m sure in hopes of regaining some license sales that were lost after the decline of the coho fisheries. However, the lake trout fishery is a big boat, specialized gear fishery, and I’m sure will not increase to any degree.

    I and thousands of other small boat fishermen would rather catch and eat a 1-3lb. coho than a 10lb. greasy lake trout. The DNR took that opportunity away from most of us, except for a very few hardy, stubborn anglers who still fish in hopes of catching one coho per angler, per trip. Even that has become an ‘iffy’ proposition.

    I wonder if the DNR is able to connect the dots, they haven’t as of yet.

  14. We have three stories about the alewife problem here: http://tr.im/glalewives

    There are a lot of charter boat captains who have built a living on taking people out for salmon and they think it would be pretty low of the fishery managers to take that away from them.

    The idea of a stable perch, walleye and lake trout fishery supported by native forage fish sounds good to me, but it apparently wouldn’t bring in license and tourist dollars like the salmon do.

  15. Lake Ontario was once full of native salmon, lake and brook trout. The carp will hurt walleye and purch populations and is something to worry about!

  16. Gordon,

    I totally agree. A lot of the big todo about the carp invasion stems from concern that this voracious invader will adversely affect the salmon fishery. But of course salmon themselves are non-native invaders that we put in the system ourselves.
    There may be plenty to worry about from the carp, but destroying the natural order of things in the Great Lakes isn’t one of them. That natural state has already been changed in a fundamental manner.

  17. Alewives are pretty troublesome, I think the lakes are better without them. I’d rather fish for walleye and perch anyhow.

    The difference between a sport fish and an invasive species seems pretty arbitrary.

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