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Sunday, 17 November 2013

Stocking Salmon in Lake Ontario (cons project)

(Updates June 1, 2015)

This was an oral presentation for a biology research project and presentation for stocking Salmon in Lake Ontario. I was assigned to present to cons of stocking Lake Ontario with Salmon, though there are many other benefits that are just not covered in this half of the assignment.

The Cons
The cons of stocking salmon generally looks towards the ecosystem in a more holistic view, then kind of zooming on specific side-effects.
  • They are non-native species, competition for native species
  • Over-Predation on Alewives
    • These are bad for the ecosystem as a whole and fishing industry
  • Heavy reliance on human maintenance

Competition for Native Species
Despite the need for more salmon, there a study conducted in 2009 shows that there is a reproducing native salmon population in Lake Ontario. The study found that the 2.3 million Chinook salmon stocked in Lake Ontario annually produce less than half of the Chinook in Lake Ontario. Most of them were born wild in streams like the Salmon River in New York, so by releasing non-native and invasive strains we are creating more competition for prey for natural strains. These non-native species reduces biodiversity of other native fish too, such as Lake and Brook Trout and American Eel, all of which are in decline in Lake Ontario.
More recent research also suggests concerns over the long-term predator-prey balance, and with other factors such as weather, other invasive species, natural reproduction and others make take unpredicted effect in changing the ecosystem’s balance. An example of dangers weather poses to populations was in 1976–1977 when alewife populations were depressed because of unusually cold temperatures.


A Threat the Alewife Population
A rising issue is that Chinook salmon in Lake Ontario are going beyond controlling the population of alewives, but are beginning to overwhelm it. Although they were an invasive species and had to be controlled after they established themselves, they have become a food supply for different predators and statistics are showing that there may not be enough anymore.
We can look to Lake Huron’s ecosystem where alewife populations collapsed in 2004, which also brought down the fishing industry with it. The collapse in Lake Huron has been attributed to the salmon stocking, which is the same thing that is being done in Lake Ontario. Mark Ebner, fish assessment biologist with the Chippewa Ottawa Resource Authority, likens trying to balance alewife populations to walking on a tightrope where “you can fall off on either side” meaning that although we don’t want too many alewives, not enough to support the ecosystem is also bad.
Past evidence of such a threat to Lake Ontario is demonstrated by past need to constantly modify the number of salmon released so as not to overwhelm the alewives; a very delicate changing balance. In the early 90s their populations were of a concern so salmonoid stocking levels were reduced to 4.5 million, and now must be maintained between 4 and
5.5 million per year.
From 1974-1977 as alewife populations went down because of predators such as non-native salmon, their prey, zooplankton, had a growing population. The balance of zooplankton population is also an important part of the lake’s ecosystem, such as being prey to algae and energy storage. These changes also cause other changes in the water-quality of the lake, including eutrophication and also contamination of other fish species. Cultural (human-induced) eutrophication led to nuisance algal blooms and water quality deterioration in Lake Ontario in the past, specifically 1940s-70s.Today there are similar issues in Lakes Huron and Ontario because of phosphorus levels and algae population, and the contamination of some fish is also a concern for human health because of bioaccumulation when fish are eaten by people.


Growing Dependence on Human Maintenance
Because of all these changes to the ecosystem management of the lake has become very complex, heavily relying on human maintenance. In 2010 the Committee on the Status of Endangered Wildlife In Canada declared the Atlantic Salmon to be extinct in Lake Ontario, as all the different strains that have been introduced to attempt to replace the extinct species from the 1800s unfortunately have failed to give any evidence of self-sustaining populations, so therefore the ecosystem relies a lot on human activity and monitoring.
Being able to maintain balance within an entire ecosystem is a heavy responsibility which has built up over time because we have to be able to maintain not only direct connection with the salmon, but also with all the other species they effect. The more human attempt to control the ecosystem, the more control it requires to be sustained so if we choose to continue to release non-native salmon into Lake Ontario, it is vital that we are prepared to handle the responsibility to reduce negative impacts on the other species living in it.


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