Changes in Lake Huron's Ecosystem
by Josh Choronzey - Owen Sound Sun Times
Thursday, April 12, 2012
I recently had a discussion with a few local anglers about salmon fishing in Owen Sound Bay. The theories and ideas among this small group of individuals had me pounding my head in disbelief. Excuses for the poor fishing ranged from cormorants to commercial netting. The fact is, to some extent they were all wrong.
The food web in Lake Huron has undergone a drastic change in recent years and the major reason for this can be directly attributed to invasive species. I recently attended a meeting between local and regional MNR representatives and a collection of sportsmen who make up the local Community Fisheries and Wildlife Involvement Program (CFWIP) clubs. Present at this meeting was MNR management biologist Arunas Liskauskas, who represents the Upper Great Lakes Management Unit. During the meeting, Liskauskas gave an informative presentation on the Huron food web and the impacts invasive species have had on the fisheries that we as local anglers have become accustomed to. I will try to summarize a few of the points to shed some light on the situation in Lake Huron/Georgian Bay.
Historically, before the introductions of non-native fish species via stocking and ocean migration through canals and locks, the lake trout was the top predator in the offshore ecosystem of Lake Huron. The lake trout preyed on cisco species, which in turn fed on zooplankton populations. This is a perfect example of the food chain prior to the meddling of man. In the 1920s and 1930s Huron was invaded by rainbow smelt and alewives, prey fish which become important later on. By the 1950s, the invasive sea lamprey and commercial fishing had nearly taken the lake trout to levels of extinction. With no top offshore predator in the mix, smelt and alewife populations were left unchecked.
With the advent of sea lamprey control, the stage was set for the introduction of salmon from the west coast, first in Michigan and then followed by Ontario in the early 1980s. Salmon not only acted as a top predatory species for the unregulated growth of smelt and alewives, but they also created a world-class fishery on Lake Huron and Georgian Bay. Huge numbers of chinooks were being stocked by Michigan and Ontario CFWIP clubs to maintain this increasingly popular sport fishery.
In the early 1990s Huron's doors were open for another round of invasive species. Enter the zebra and quagga mussel, the spiny water flea, and the round goby. Zebra and quagga mussels are filter feeders, forming massive colonies and siphoning the key microscopic nutrients out of a water body. The effect that zebra and quagga mussels have had on Huron has been dramatic. Over a decade and a half, these mussels have effectively cleaned the water and plankton and zooplankton numbers have plummeted. These micro-organisms are the building blocks for prey fish populations. No food for zooplankton equals no food for prey fish such as alewife, which in turn leaves little for the massive numbers of salmon to feed on.
In 2003 and 2004, DNR and MNR lake samples indicated that the alewife population had crashed. In the following years local salmon fishermen noticed that the overall health of mature chinooks was poor. Gone were the robust salmon of yesterday; the remaining chinooks were long and skinny, showing signs of malnutrition. MNR and DNR response was to cut back stocked numbers of chinooks to accommodate the wild recruitment of salmon, which has been taking place on Huron for the past two decades. Still, alewives are nearly non-existent, and large, healthy salmon populations require alewives to thrive.
The current outlook for chinook populations on Huron and Georgian Bay are not that much better. Stocking numbers have been reduced on both sides of the border, as a good portion of the overall population of chinooks has been shown to be wild fish born in local rivers. The food supplies for pelagic predators such as chinooks are still limited. There is very little evidence that the alewife numbers will rebound. Salmon do not effectively feed on gobies, or warm-water prey fish such as perch. The increasing number of local shiner populations does not fill the void when it comes to offshore species such as chinooks either.
So is this all doom and gloom? No, not entirely. Alewives have proven to be a major predator of perch and walleye young. Since the alewives crashed in 2003, walleye and perch numbers have risen across the lake. Natural reproduction of walleye in Michigan's Saginaw Bay in recent years has been the highest ever recorded. This is good news for those who like to fish for these warmer water species and good news for commercial fisherman as well. This pattern can be seen locally as well. In the past couple of years more walleye and perch have found their way into anglers' catches along the Huron shoreline. Also, studies have shown that lake trout natural reproduction has begun to increase with the changing diet of adult lake trout. While not the prime target species of anglers, lake trout appear to handle a shift in the food chain better than chinooks.
Last week, I had the opportunity to see exactly what the change in Huron's food web has resulted in. Along with two friends, I had some of the best jumbo perch fishing I have ever experienced, and it took place on Lake Huron. Good catches of perch have been reported from the inner harbour of Owen Sound, to the upper shores of Huron along the Peninsula. I guess change isn't always bad . . .