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This study reflects on diverse ecosystem factors affecting fish relationships in estuarine ecosystems across multiple decades. Observations show consistency in relationships despite significant food web changes, with unclear mechanisms. Despite challenges in testing mechanisms and limited funding, continued data collection is vital for future research.
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X2 reflects many ecosystem factors Physical Habitat changes Water Quality Contaminant effects Larval dispersal Adult migration and spawning X2
X2 X22 X12 X32
Fish- X2 Relationships From Kimmerer 2002 1967-87 1988-2000 1982-2000 (DS) All Years
X2 observations Fish:X2 Relationships maintained across 35 years of data Massive change in food web had little impact on relationships Mechanisms remain unclear and probably diverse
Future Directions • Research strategy under development (CBDA grant to Kimmerer and Bennett) • Limited ability to test mechanisms • Reduced funding likely to restrict studies • Discussion with local biologists suggest that, for many possible mechanisms, variability is likely important (Estuarine Ecology Team July 2004)
Conclusions • X2 seems to be working to protect aquatic resources from reductions in estuarine habitat quality • Protecting both mean and variance of X2 seem important • Unlikely that more effective ways to protect resources will be found soon • Continued data collection is vital for meaningful review
Main references • Kimmerer, W.J. 2002. Physical, biological, and management responses to variable freshwater flow into the San Francisco estuary. Estuaries 25:1275-1290 • Jassby, A.D., W. J. Kimmerer, S.G. Monismith, C. Armor, J.E. Cloern, T.M. Powell, J.R. Schubel, and T.J. Vendlinski. 1995. Isohaline position as a habitat indicator for estuarine populations. Ecological Applications 5:272-289