The Great Lakes: A Natural History of a Changing Region is the most authoritative, complete and accessible book to date about the biology and ecology of this vital, ever-changing terrain. Written by one of Canada's best-known science and nature writers, it is intended not only for those who live in the Great Lakes region, but for anyone captivated by the splendor of the natural world and sensitive to the challenges of its preservation. It is both a first-hand tribute and an essential guide to a fascinating ecosystem in eternal flux.
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About the Author
Read an Excerpt
From The Prologue:
I was born on the Great Lakes. Actually, I was born between two Great Lakes, in Windsor, Ontario, across from Detroit, Michigan, in that odd little linkage - Detroit River, Lake St. Clair, St. Clair River - between Lake Erie and Lake Huron. In the shadow of the Ambassador Bridge, at the mouth of the Detroit Tunnel. The joke in Windsor is that the light at the end of the tunnel is downtown Detroit.
Windsor is a curious city, almost Mexicanized. We looked north to the United States, across the riverine international border. I remember skating on Lake St. Clair, on transparent ice that had frozen so quickly it was still in the shape of waves. I looked down giddily beneath my bobskates to see schools of minnows dart among waving fronds of bottom-anchored plants. I remember swimming in Lake Erie, off Point Pelee, and being taken to visit the now-legendary Jack Miner, who was then working hard at his bird sanctuary near Leamington to save the threatened Canada goose from extinction, an endeavour in which he succeeded admirably.
My father's family had moved to Windsor from Cass County, Michigan, at the end of the 19th century, a move that took them due east, not north. Cass County was named for Michigan Territory's first governor, Lewis "Big Belly" Cass who, with Thomas McKenney and Henry Rowe Schoolcraft, travelled around Lake Superior in 1825 signing Indian treaties and searching for "any metals or minerals from any part of their country" that would lure future settlers to the territory. By the time my father's family moved to Michigan, shortly after the American Civil War, Cass County was a major stop on the Underground Railroad. My great-grandfather, Andrew Jackson Grady, had a cup of coffee there, as they say in major-league baseball, before moving on to Windsor.
We later lived for a time north of Toronto, on Lake Simcoe, which is part of the ancient water route through which, 4,000 years ago, Lake Huron drained directly into Lake Ontario, bypassing Lake St. Clair and the Detroit River and Lake Erie altogether. And I have a brother living in Sault Ste. Marie, Ontario, across the St. Mary's River from Sault Ste. Marie, Michigan, the former home of Henry Rowe Schoolcraft. Thus the web of my family embraces the five Great Lakes and two of the three linkages between. At the risk of sounding melodramatic, and at the further risk of causing my body to be disposed of as toxic waste when I die, it is not too much of an exaggeration to say that I have Great Lakes water flowing in my veins. If, as I believe, our true homes are ecosystems, not geopolitical entities, then my home territory is the Great Lakes basin .
From Chapter 7, "Water":
The first non-indigenous species recorded in the Great Lakes has arguably been the one that has had the most long-lasting and deleterious effect. The sea lamprey (Petromyzon marinus) first appeared in Lake Ontario in 1835, and its subsequent conquest of all five lakes has been called "a biological legend," comparable to that of the introduction of the rabbit to Australia. The saga of the sea lamprey reads like a template for the many other pernicious species that have since invaded the system, from the alewife to zebra mussels.
The lamprey is the most primitive vertebrate known to science. Fossil evidence shows it to have been around for the past 400 million years. It looks like an eel, but that is a deception that can have dire consequences: England's King Henry I is thought to have died from eating "a surfeit" of sea lampreys, thinking they were eels. A lamprey is little more than a spine and a digestive track, with a mouth at one end and an anus at the other; it has no jaws and therefore no teeth, rather rows of sharp protuberances on its tongue and lips. It breathes through gill pouches arranged along the length of its body, which is covered by a layer of slime, and feeds by attaching its mouth to the side of a fish, lacerating the fish's flank with its tongue, and then sucking the bodily fluids out of it. An anticoagulant in its saliva keeps the juices flowing freely. Fish have been caught in the Great Lakes with eight or ten lamprey scars on their sides and three or four lampreys still hanging off them, still sucking away. A lake sturgeon was once caught in Lake Michigan with eighteen lampreys attached to it. Such fish are usually thrown back. "They cook dry," one fisherman has commented
Lampreys were first recorded in Lake Ontario in 1835, but some believe they had always been there, as well as in Lake Champlain and the Finger Lakes of upper New York state. Others think they originated in the Atlantic Ocean and entered Lake Ontario via the Erie Canal, which opened in 1825. In any case, the lamprey population remained stable and confined to Lake Ontario for almost 100 years, even though the Welland Canal opened to shipping in 1829. They caused severe damage to several Lake Ontario fish populations including ciscoes, lake trout and walleye but did not migrate further upstream into Lake Erie until 1921, two years after the Welland Canal was deepened to allow larger ships into the Upper Lakes, and when the supply of sizeable prey species in Lake Ontario had been sufficiently reduced.
By 1936 they were reported in Lake Michigan, the following year they showed up in Lake Huron, and were in Lake Superior in 1946 . Lake trout, cisco and walleye were hit hard because lampreys feed only on large fish, adults greater than 17 inches in length. Lake trout reach that size in about four years, but do not become sexually mature until they are six or seven years old; most are either weakened or killed by lampreys before they are old enough to reproduce. As fish populations plummeted, the lamprey population soared, increasing 20- to 50-fold per generation throughout the 1940s and '50s. The population peaked in 1961, and the following year commercial fishing of lake trout was prohibited. By that time there were hardly any lake trout anyway, and even the lamprey had turned to other species, and similar declines started showing up in burbot, lake whitefish, suckers, lake herring and even large chub.
Attempts to control lampreys began in Lake Superior in the 1960s, in order to try to preserve genetic pools of lake trout that could be hatchery-reared and used to re-seed populations in the other Great Lakes. Various methods were tried, including the release of neutred males and electrocution huge electrical probes were inserted into the water at dam sites along freshwater streams known to be spawning beds for lampreys. The most successful control was a chemical larvacide called 3-trifluormethyl-4-nitrophenol (TFM for short), developed by Vernon Applegate, a U.S. Fish and Wildlife biologist at the Hammond Bay Biological Station in Michigan. TFM is toxic to all fish, but fish have livers that can filter it out. TFM was first sprayed on spawning streambeds in 1962, and by 1966 the lamprey population had been reduced to 5 percent of its former size.
The population remained low for several years. The Lakes were restocked with lake trout fingerlings in the hope that they would reclaim their original dominance, and in some lakes the strategy seemed to be working. Studies in the 1990s suggested the lake trout population was large enough for stocking to be no longer necessary; in Lake Michigan, it was thought to be exceeding historical levels. Then sea lamprey numbers began to climb again, probably as a result of improvements to the St. Marys River, between Lake Superior and Lake Huron, undertaken in the 1970s to make the river a more hospitable habitat for lake trout and other salmonids.
The lamprey population in the Upper Lakes now is nearly as large as it was in the early 1960s, and there seems no effective way of controlling it. Stocking lake trout in Lake Superior was halted in 1996 because it was basically just feeding lampreys: from 1995 to 1999, lampreys killed 500 tonnes of lake trout every year. In Lake Huron, only 17 percent of the lake trout population survive each year; 10 percent die naturally, 19 percent are caught by commercial and sport fisheries, and 54 percent are killed by sea lampreys. Like death and taxes, sea lampreys will apparently always be with us.
Table of ContentsPrologue
1 The Freshwater Seas
2 Foundation Stones
3 The Boreal Forest
4 The Great Lakes-St Lawrence Forest
5 The Carolinian Forest
6 Special Habitats: Wetlands, Alvars, and Urban Forests
9 The Future
Appendix: Scientific Names
Illustration and map credits