Fishery habitat in estuaries of the U.S. Gulf of Mexico: a Comparative Assessment of Gulf Estuarine Systems (CAGES)

The total estuarine area potentially available for exploitation by fishery species was highly variable among the 24 estuaries ranging from around 15,000 ha in Perdido Bay to over 600,000 ha in Breton-Chandeleur Sounds, with this area generally largest in systems from northern Texas through Louisiana. The most abundant estuarine habitat was generally Estuarine Emergent Marsh, following a spatial pattern similar to the total estuarine area with the highest values in Louisiana estuaries. Although areas of Estuarine Aquatic Beds were identified, confidence in these results were relatively low, due to limitations of the remotely sensed data. Marsh edge was measured in a variety of ways using both C-CAP and NWI data, and edge was greatest in Louisiana estuaries. Flooding of the marsh edge also was high in most of the 13 estuaries examined; lowest values were from Louisiana marshes just east of the Mississippi River.

We used the USGS Estuarine and Coastal Drainage Areas to identify estuarine boundaries for analysis. Habitats within estuarine systems were identified using data from NOAA's Coastal Change Analysis Program (C-CAP) and the USFWS National Wetland Inventory (NWI). Our analysis centered on estuarine emergent marsh, and in addition to the amount of marsh in each system, we identified the amount of marsh edge. Analyses were conducted using ESRI ArcView 10.2 software with the Spatial Analysis Extension and the Polygon Neighbors tool. We also estimated the amount of time that the marsh edge was flooded in 2013 for 13 of the estuaries.

The total estuarine area potentially available for exploitation by fishery species was highly variable among the 24 estuaries ranging from around 15,000 ha in Perdido Bay to over 600,000 ha in Breton-Chandeleur Sounds, with this area generally largest in systems from northern Texas through Louisiana. The most abundant estuarine habitat was generally Estuarine Emergent Marsh, following a spatial pattern similar to the total estuarine area with the highest values in Louisiana estuaries. Although areas of Estuarine Aquatic Beds were identified, confidence in these results were relatively low, due to limitations of the remotely sensed data. Marsh edge was measured in a variety of ways using both C-CAP and NWI data, and edge was greatest in Louisiana estuaries. Flooding of the marsh edge also was high in most of the 13 estuaries examined; lowest values were from Louisiana marshes just east of the Mississippi River.

The estuaries we examined appear to vary greatly in their capability to support coastal fishery populations based on their nursery habitat. Estuaries near the Mississippi River Delta have the greatest potential for providing essential nursery support for fishery species, and these estuaries do support high abundances of the young of fishery species based on survey data from long-term monitoring programs of Gulf coast states (Brown et al. 2013). The characteristics that these estuaries have in common include large areas of emergent marsh and marsh edge habitat, high rates of flooding at the marsh edge, and elevated nutrient inputs from the Mississippi and Atchafalaya Rivers. Seagrass and SAV are also important for fishery species, but our ability to quantify the area of this habitat in GoM estuaries is limited by available remote-sensing technology.

To assess variability in overall estuarine area within watersheds, the amount of different fishery habitats in each estuary, and some habitat characteristics that may be important in supporting fishery species.

T.J. Minello, P. Caldwell, and L.P. Rozas 2017. Fishery habitat in estuaries of the U.S. Gulf of Mexico: a Comparative Assessment of Gulf Estuarine Systems (CAGES). U.S. Dept. Commerce NOAA Tech. Memo. NMFS-SEFSC-702, 48 p.

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