The Fishery Value of Salt Marsh Restoration Projects
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We assessed the benefits of different wetland restoration techniques for fishery resources by comparing habitat complexity, fishery support, and construction costs among five salt marsh restoration projects in Galveston Bay, Texas. The restoration projects included marsh terracing at Galveston Island State Park (GISPT) and Pierce Marsh Preserve (PMPT), mound construction at Jumbile Cove (JC), and marsh island construction north of Galveston Island along Interstate Highway 45 at 1-45 East Marsh (I45EM) and I-45 West Marsh (I45WM). The projects were located in shallow estuarine waters and used bottom sediments or upland soils to construct intertidal areas that were planted with smooth cordgrass Spartina alterniflora. We used a Geographic Information System (GIS) and high-resolution aerial photography to classify areas into land (marsh vegetation) and water and applied fishery density models to assess fishery support. These models were developed to describe fine-scale distribution patterns for brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus across shallow estuarine habitat types (emergent marsh and shallow open water) of the Galveston Bay estuary. Restoration sites ranged in size from 6.9 ha (I45EM) to 68.2 ha (GISPT). Construction costs ranged from $362,250 (GISPT) to $74,200 (I45EM). Costs standardized to 1 ha for comparison among projects were $40,608 (I45WM), $11,875 (JC), $10,685 (I45EM), $8,771 (PMPT), and $5,310 (GISPT). The I45WM project contained the greatest percentage of marsh vegetation (68%), whereas the two terracing projects had the smallest percentage (PMPT = 18%, GISPT = 19%). More of the constructed marsh in the terracing projects, however, was vegetated marsh edge (located within 1 m of the marsh shoreline) than in other projects (PMPT = 29%, GISPT = 25%, I45EM = 20%, JC = 11%, I45WM = 9%), and this habitat type supports the greatest densities of fishery species. Based on our modeling analysis, overall fishery support was greatest for the two 1-45 projects, followed by the PMPT terracing project. Estimates of standing crop (number of animals) standardized to 1 ha ranged between 22,246-30,863 for brown shrimp, 21,773-33,139 for white shrimp, and 17,240-24,927 for blue crab. The two terracing projects and I45EM had higher fishery-benefit:cost ratios (ratio of standardized net fishery value to standardized project cost) than the other projects. Although marsh terraces composed of small cells supported the highest nekton populations, terraces constructed of medium cells were more cost-effective than terraces composed of either small or large cells. Based on our modeling results, all five restored sites supported relatively high populations of fishery species compared to prerestoration conditions. However, restoration sites did not support populations equivalent to a reference marsh system. Restoration projects should maximize the area of marsh vegetation and create a high degree of water-marsh interspersion to provide the most benefit for fishery species.