Are Salmon in the Great Lakes Natural?

The simple answer is NO!  After my post of Monday describing the migrating salmon we went to see in Owen Sound, I started reading more background info, and got way off on a tangent.  But it's a very interesting tangent.  The story of fish populations in the Great Lakes is a long and complex one, and the fish populations, including those salmon and steelhead that fishermen line up along the banks to catch today, are definitely not natural.

I`ve done a lot of reading, but I`m not going to give you references!  This is still quite a superficial overview, but it`s my simplified story of the evolution of Great Lakes fish populations as I understand it. 

The history of the Great Lakes fisheries usually takes you back to the booming fish catches of the 19th century, but the story really begins much earlier.  Native peoples have been fishing the Great Lakes for thousands of years, with many villages located at the mouths of rivers and streams, reflecting the availability of a rich food source when the fish were migrating.

The indigenous villages or sites of known seasonal encampments around here are all located at the mouths of streams, the Saugeen, the Pottawatami, and the Bighead right here in Meaford.  I can't resist mentioning that the west coast native tribes had the richest culture, benefitting from the salmon runs in B.C.  The availability of that rich food source underlies the potlatch tradition, and explains how they had time to carve those amazing totem poles!

The next story though is of those 19th century fisheries.  Depending largely on the native Lake Trout and Whitefish populations, the catches boomed, but this led to serious over-fishing within only a few decades.  The native Atlantic salmon (which could migrate up the St. Lawrence in the days before any dams were built) were driven to extinction in the Great Lakes quite early.

The end of the Great Lakes Trout populations came with the explosion of Sea Lamprey populations in the 1940s.  These eel-like creatures latched onto the fish and literally sucked the lifeblood out of them.  Fisheries collapsed, though a few Whitefish survived and are still caught today.  The Sea Lamprey were eventually controlled by using lampricide in the small streams where their larvae are killed before they get a chancer to grow.

The next invader was the Alewife.  Alewife populations grew steadily until during the 1960s they exploded and started dying off in mass shoals of dead fish along the shorelines.  Because of the eutrophication from fertilizer runoff and sewage, the Great Lakes were described as 'dead' by 1969.  The International Joint Commission held hearings into what to do about Lake Erie, which was the worst affected.  

In fact when I was in 3rd year of university in London Ontario, I went and appeared before that Commission (as a young student 'radical') and bemoaned the problems they were leaving for my (our) generation.  That was one of the first times I got publicly involved in environmental issues, in those heady years of the first Earth Day!

Starting in 1966 the department that oversaw sport fishing in Michigan thought it could control the Alewife problem by introducing Pacific Salmon.  Remarkably, the stocking program was a success.  In a few years we had a booming population of Coho and Chinook Salmon in the Great Lakes, and the Alewife overpopulation was being controlled by those salmon.

Steelhead and Rainbow are actually the same species of fish..  The fish that migrate, like salmon, and spend 2-4 years in open water, are known as Steelhead.  Those that have become residents of rivers and streams and stay there to live are known as Rainbow.  They were initially stocked in the late 19th century, and have spread naturally, but they have been only partly successful in reproducing naturally and depend on continued stocking.  

For a few years in the 1980s and 1990s it was all a developing success story.  The widespread research into and adoption of conservation tillage in farming (some led by the department in which I taught at Guelph), improved water quality a lot.  The building of sewage treatment plants in Chicago, Detroit, Cleveland and Buffalo did a great deal more.  The lakes were looking much healthier, and sport fishing was booming.

Then the Zebra Mussel arrived, followed by the even more deadly Quagga Mussel.

Tiny dime-sized molluscs that live on the lakebed, these mussels filter water, an enormous amount of water, sucking up the phytoplankton (minute plant life) that is the foundation of the foodchain.  The zooplankton (tiny animal life) go next, and soon there is no food for baby fish.  The waters get clearer and clearer.  In places it looks like a tropical lake now!  The Zebra Mussel prefers warmer surface or shallow water, so it`s limited to those areas, but the Quagga Mussel can live in tremendous depths of water.  In places the entire lakebed is now carpeted for miles and miles.

Although there has been some limited success in controlling the accumulation of mussels on docks and water intake pipes, no widespread solution has been found.  They are invasive species from the Black Sea area, carried in the ballast waters of ships.  Rules are now in place to at least prevent this from continuing, with complete mid-ocean seawater flush of ballast tanks now required before ships enter the St. Lawrence Seaway.  But the mussels that are here appear to be here to stay.

So we are left with an uneasy balance of life in the Great Lakes.  Salmon are still providing great sports fisheries, though not in the volume of 20 years ago.  Whitefish and others provide limited commercial fishing, but not in anything like the volumes of the last century.  Some argue that we should stop the artificial stocking of salmon and steelhead to encourage the native Lake Trout.  But the mussels are now the foundation of a very uncertain future.

Here`s hoping the next generation can take over managing the lakes effectively!