BULLETIN OF MARINE SCIENCE, 83(1): 197–215, 2008 197 Bulletin of Marine Science © 2008 Rosenstiel School of Marine and Atmospheric Science of the University of Miami MOTE SYMPOSIUM INVITED PAPER LIFE HISTORY, HISTORY, HYSTERESIS, AND HABITAT CHANGES IN LOUISIANA’S COASTAL ECOSYSTEM James H. Cowan, Jr., Churchill B. Grimes, and Richard F. Shaw ABSTRACT Perhaps the most perplexing aspect of the highly engineered and artiicial Missis- sippi River deltaic ecosystem is lack of evidence that ish production has decreased. Louisiana accounts for ~75% of the ishery landings in the U.S. Gulf of Mexico and 60%–80% of the nation’s total annual coastal wetland loss, the human-caused rea- sons for which are well documented. Continued alteration, degradation, and loss of Louisiana’s estuarine and wetland habitats makes knowledge of the relationship be- tween habitat stability, and its efects on nursery-ground function and ish produc- tion, critical. As a result of this issue in Louisiana and elsewhere, concepts of ecosys- tem management and sustainable development have become part of state, national, and international dialogue about adaptive environmental management. Formula- tion and implementation of long-term, sustainable coastal policies and integrated management strategies demand a better understanding of (1) habitat and ecological stability and associated functional responses to both episodic and chronic insults, especially given the limited vitality of already-stressed coastal ecosystems, and (2) the compounding and complex efects of multiple impacts superimposed on issues associated with shifting baselines and climate change. A number of investigations have demonstrated relationships between isheries yields and the high nutrient loads, freshwater inputs, shallow depths, large areas of tidal mixing, coastal vegetated area, surface area of lagoon-estuarine systems, and resulting high productivities that are typical of estuaries and estuarine plume ecosystems (see Deegan et al., 1986; Nixon, 1988; Iverson, 1990; Sánchez-Gil and Yáñez-Arancibia, 1997; Yáñez-Arancibia et al., 2004). As a result of these relation- ships, and despite the small aggregate spatial extent of estuaries (< 1% of the global marine area), a fraction exceeding 50% of U.S. ishery yields have historically been derived from estuarine or estuary-dependent species (Gunter, 1967; McHugh, 1967; Houde and Rutherford, 1993; Vidal-Hernandez and Pauly, 2004). In the Gulf of Mex- ico (hereafter the Gulf), the fraction is considerably higher (Houde and Rutherford, 1993); estuary-dependent species dominate in large and valuable commercial and recreational catches (e.g., gulf menhaden, Brevoortia patronus Goode, 1878 support the second largest U.S. ishery by weight, and penaeid shrimps support the ifth larg- est by value; shrimp landings alone are valued at $400–$500 million per year). A signiicant fraction of the harvested secondary production in the western Gulf’s “fertile crescent” (Mississippi River mouth to the northern tip of the Yucatán Penin- sula) is derived from estuarine ecosystems, including areas on the shallow shelf inlu- enced by estuarine plumes (Darnell, 1990; Christensen and Pauly, 1993; Sánchez-Gil and Yáñez-Arancibia, 1997; Chesney and Baltz, 2001; Day et al., 2004). Characteristic of these estuaries are high river discharge rates, large freshwater surpluses, and low water residence times (Deegan et al., 1986). Much of the production and subsequent trophic transfer may therefore occur outside the physical boundaries of the estuar- ies, i.e., in association with plumes of fresh water over shallow continental shelves. hese contrasting sources—estuary and shelf—of trophic delivery to the ishery for-