Geoscience Reference
In-Depth Information
This pattern appears early, first during the Roman period, when highly valued oysters were depleted in Itali-
an waters two thousand years ago and subsequently had to be imported from the North Sea. The oyster fishery
there finally succumbed to centuries of overexploitation in the early 1900s. On this side of the Atlantic, a sim-
ilar loss of the once-extensive oyster beds in Chesapeake Bay occurred in the late 19th century.
Heike Lotze of Dalhousie University in Halifax, Nova Scotia, is a world leader in the emerging field of mar-
ine historical ecology and has demonstrated that the pattern of land-to-shore-to-deep-sea exploitation has been
repeated many times. She has meticulously documented the ecological decline of the world's largest intertidal
system, the Wadden Sea, which has one of the most complete records of human exploitation, dating to the
Neolithic.
As early as five thousand years ago, the local tribes were making the transition from hunting and gathering
to a settled life of farming and fishing. Marine fish gradually became more important as a staple for these
coastal people, replacing marine and land mammals, coastal birds, and molluscs. Then, during the Middle
Ages, subsistence fisheries evolved into commercial enterprises, driven by market demand from the European
inland, where freshwater and anadromous fish stocks like salmon had already been wiped out. By 1800, local
haddock, sturgeon, and oyster stocks had been depleted by half, and eventually European sturgeon, Atlantic
salmon, shad, sea trout, and the European oyster were driven to extinction in the Wadden Sea. By 2000, the
only commercial fishery resources left were shrimp and blue mussels.
This pattern of exploitation and depletion, sometimes ending in extinction, was common to the coastal eco-
systems around Europe and by the end of the Middle Ages had driven fishers to the offshore regions in the
North Sea and Iceland. Eventually, the loss of local nearshore resources led European fishers to the North
American side of the Atlantic, where the patterns—a kind of domino effect—have been repeated on a more
compressed timescale but with no less devastating results.
Lotze has applied her probing methodology to this side of the Atlantic with an in-depth analysis of the
Quoddy Bay region of southwestern New Brunswick, in the outer Bay of Fundy. Enriched by the outflow of
the Saint John and St. Croix River watersheds and driven by marine upwellings, this is one of the most pro-
ductive coastal regions in eastern North America. As the noted oceanographer A.G. Huntsman once observed:
“Nowhere else in the world (this may be questioned) are there waters to compare with those of Passama-
quoddy Bay and vicinity, where such vast quantities of fish are taken yearly from a small area.” Aboriginal
people of the Quoddy Tradition gave it its name, which means “Bay of Pollack.” These early residents dined
on a cornucopia of marine species, including fishes (cod, pollack, herring), invertebrates (clams, blue mussels,
sea urchins), mammals (gray and harbor seals), and a variety of marine birds (common loon, brant, even great
auk). While they exploited a diversity of organisms from all trophic levels of the food web over two to three
thousand years, their subsistence economy did not result in depletion or extinction of a single species. The
consequences of European colonization, however, were in sharp contrast.
The changes to the marine environment came from all directions: “top-down” through exploitation,
“bottom-up” from nutrient loading leading to oxygen depletion (or eutrophication), and “side-in” by habitat
destruction and pollution. Exploitation began with whaling and a seasonal cod fishery in the 16th and 17th
centuries but upon settlement of the region in the 18th century quickly expanded to include most marine spe-
cies, of which herring and lobster were among the most important. The decline of groundfish species in the
1960s and 1970s—and their eventual commercial collapse in the 1990s—led to a practice that has been called
“fishing down,” whereby fishing is first directed at long-lived, fish-eating species such as cod and then, when
they have been depleted, to ever-lower trophic levels: first to plankton-eating fishes such as herring and then,
as in the Quoddy region, to invertebrates such as shrimp and crab, and finally, in the 1980s and 1990s, to rock-
weeds, the primary producers. In effect, this amounts to a sequential mining of marine resources—going ever
lower in the food chain and stripping out each level of the system—which ultimately can lead to major
changes in the structure of the marine food web itself.
