Data Sets Relevant to Identification of Essential Fish Habitat (EFH) on the Gulf of Mexico Continental Shelf and for Estimation of Effects of Shrimp Trawling Gear
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Our objectives were: to identify data describing habitats, shrimp trawling, and other human activities on the Gulf of Mexico continental shelf; to incorporate such data into a GIS format; and to provide preliminary experimental designs for assessment of effects of shrimp trawling on EFH. We developed 57 data layers describing habitat (benthic organism densities, sand/silt/clay, digitized sediment and biotic community maps), structures (bathymetry, State/Federal waters, safety fairways, oil and gas, artificial reefs, bottom obstructions), and fishing (patterns of shrimp fishing effort, experimental trawling sites/catches, closed waters). Best opportunities for experimental trawling in closed waters lie in southern and northwest Florida (permanent closures) and in Texas (seasonal closures). Experiments in open waters need to account for seasonal closures, ambient shrimping effort, and variations in sediments and their associated benthic communities. Cross-Gulf replication is necessary to provide a fishery-wide assessment of gear impacts. Most opportunities for replication exist at depths of 18-27 m for both sand and mud habitats. Moving to waters only as deep as 46-55 m forces experiments to become more regional and less Gulf-wide in nature. Benthic data are most dense off south Texas and Mobile Bay, less dense off Florida, and are largely absent off west Louisiana and north Texas. Non-extractive or no-take marine reserves could be used to study effects of complete cessation of trawling on habitats and fauna (estimating recovery rates of ecosystem components, conducting fishery-free gear impact studies). We present only a few options - data sets are available on CD.