Wednesday, May 23, 2012

Desperate Alewives and Cod without Rivers

Noaacod1In the often-sad history of fisheries management, few tragedies are more prominent than the decline of the North Atlantic cod.  Cod once were phenomenally abundant—so much so that many believed their populations were inexhaustible—but collapsing populations in both Canadian and American waters proved that conventional wisdom wrong.  For the fishing communities of New England and the maritime provinces, the consequences were devastating.  The aftershocks continue to the present day.  Rebuilding cod and other groundfish populations remains a struggle, and battles over fishing restrictions still rage.

Recently, a team of researchers at Bowdoin and Bates Colleges and the University of Southern Maine  began exploring a new angle on fisheries restoration.  Traditional fisheries regulation in New England, as in most U.S. waters, has focused primarily on regulating the number of fish caught.  Habitat protection is less frequently the focus, particularly if the habitat is somewhere other than the fishing grounds at issue.  But this research team’s working hypothesis is that a key step toward bringing back New England’s marine fisheries may be restoration of the region’s freshwater rivers.

AlewifeAt first blush, that statement may seem odd, for cod and other groundfish live their entire life cycles in the ocean.  Some of their prey, however, are another story.  New England’s lake and river systems once poured literally millions of diadromous fish into nearshore waters, and those fish—salmon,eels, shad, and, most abundantly, river herring—formed part of the base of the marine food chain.  But beginning in the nineteenth century, a combination of logging drives, pollutant discharges, and dams decimated those populations, transforming not just freshwater ecology but also the adjacent oceans.  That loss of food may have been an important contributor to the groundfisheries' near-demise.

Edwards-before-afterThe logging drives have ended, and, thanks to the Clean Water Act, water quality, though still problematic in places, is vastly improved. Hundreds of dams remain, and they create significant impediments to the recovery of diadromous fish populations, but that, too, is starting to change.  In the 1990s, the Federal Energy Regulatory Commission ordered the removal of the Edwards Dam on the Kennebec River (pictured at left; photos from  Several other dam removals have followed, with the Penobscot River Restoration Project—perhaps the most ambitious dam removal project in the country—beginning to remove structures this year.  At a minimum, these projects create great opportunities for studying the ecology, economics, and politics of dam removal, and the Bowdoin-Bates-USM research team is already working to take advantages of those opportunities.  Perhaps, also, those dam removals will be a step toward the restoration of an iconic fishery.

For more on the rivers, fish, and research, check out this (Emmy-nominated) documentary.

Watch Desperate Alewives on PBS. See more from Sustainable Maine.

 - Dave Owen

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