Outside the Pacific Northwest, places that still have abundant salmon are fighting to keep it that way. Bristol Bay in Alaska is home to the most valuable salmon fishery in the world. Bad news for salmon: a massive deposit of gold and copper was found in the headwaters and one of the biggest open pit mines in the world has now been proposed for. An Olympian struggle has ensued between residents and the proposed developers.
Graph models reveal historic Chinook and steelhead metapopulations as falling between “classic” or “Mainland-island” metapopulation structure, that is, having moderate connectivity and either roughly equal population sizes (“classic”) or highly variable population sizes (“Mainland-island”). Remember that key criteria for metapopulations are discrete habitat patches and some limited dispersal between patches, criteria that would be characterized as moderate connectivity. The modeled dam scenario consistently reduced connectivity between populations leading to a “nonequilibrium” metapopulation state. “Nonequilibrium” is not a good thing: with less connectivity, vulnerable populations are less likely to get reinforcements. In contrast, in the hatchery scenario, the high straying rates for hatchery fish led to increased connectivity. The resulting structure might be described as “patchy” or “panmitic” with so much flow between populations that the metapopulation acts as one big population with everyone in step. A model that combined dams, hatcheries and habitat degradation, our current state of affairs, displayed metapopulation structure with low connectivity and variance in population size, again the “nonequilibrium” state.
1. Ben Knight. http://ourbristolbay.com/photo-gallery.html
3. from Schindler et al. (2010)
4. from Hilborn et al. (2003)
5. from Fullerton et al. (2011)
6. Steve Cowgen, Michael Milstein. The Oregonian. http://blog.oregonlive.com/news_impact/2008/10/dam.jpg
2. Hilborn, R., T.P. Quinn, D.E. Schindler, and D.E. Rogers. 2003. “Biocomplexity and Fisheries Sustainability.” Proceedings of the National Academy of Sciences 100 (11): 6564.
3. Moore, J.W., M. McClure, L.A. Rogers, and D.E. Schindler. 2010. “Synchronization and Portfolio Performance of Threatened Salmon.” Conservation Letters 3 (5): 340–348.
4. Rogers, L.A., and D.E. Schindler. 2008. “Asynchrony in Population Dynamics of Sockeye Salmon in Southwest Alaska.” Oikos 117 (10): 1578–1586.
5. Schindler, D.E., R. Hilborn, B. Chasco, C.P. Boatright, T.P. Quinn, L.A. Rogers, and M.S. Webster. 2010. “Population Diversity and the Portfolio Effect in an Exploited Species.” Nature 465 (7298): 609–612.