Friday, November 27, 2009

Historic Abundance and the Shifting Baseline

Photo from Dave Vedder

Throughout much of their historic range, wild salmon and steelhead abundance is only a fraction of its former size. As we implement recovery measures it is important that we understand the magnitude of abundance, and diversity that once existed in our watersheds. With little knowledge of historic habitat condition, and abundance of salmonid species, most agency estimates are based on our limited understanding of how precontact watersheds looked and how present day habitat conditions relate to drive productivity and abundance. Contrasting this approach is work by Bill McMillan and Nick Gayeski of the Wild Fish Conservancy which relied on historic cannery and catch records to paint a picture of what we've lost. While somewhat limited in its geographical scope, their work is the most comprehensive and accucrate estimate of historic abundance available, at least in the watersheds with canning records available. Their report details historic returns that border on unimaginable to present day anglers, with tens of thousands of wild steelhead returning to many systems and declines in the neighborhood of 80-98% in most areas. While their findings are discouraging, accurate estimates of historic abundance allow us to more effectively advocate for real recovery in wild salmon and steelhead populations around the region. Salmonid fish evolved in dynamic systems, prone to periodic disturbance and massive localized declines. Human impacts in the last century represent only the latest in a long series of disturbances. Fortunately salmon and steelhead are extraordinarily resilient, over the last 10,000 years salmon and steelhead have recolonized most of their present range from ice free refugia following the recession of pleistocene glaciers. Barring catastrophic extinction through most of their range, fish will undoubtedly recover their historic abundance at some point in the future. However, without honest accounting on the extent of loss and ambitious, science driven recovery measures we will certainly not see anything close in our lifetimes.

Check out McMillan and Gayeski's article at the Wild Salmon Center's website

A summary of the paper by Pete Soverel in Osprey Vol. 54

No comments: