Pete Sheridan and Jennifer Doerr

There are very few areas of the U. S. Gulf of Mexico continental shelf that are closed to the shrimp fishery, which operates primarily from shoreline to 90 m (50 fm) depths. There is a window of opportunity, however, to study the short-term effects of the cessation of shrimp trawling on benthic habitats. In 2000, Texas Parks and Wildlife Department enacted a seasonal closure of nearshore waters  to all shrimp trawling of the southern Texas coast between Corpus Christi Fish Pass and the US-Mexico border. The Southern Shrimp Zone (SSZ) encompasses waters from the shoreline out 9.3 km (5 nmi) during the period December 1 until the opening of the brown shrimp season, usually during July 1-15 each year. There is a complimentary Northern Shrimp Zone (NSZ) extending from Corpus Christi Fish Pass to the Texas-Louisiana border, but daytime trawling is permitted out to 5.6 km (3 nmi). This 7-month SSZ closure permits several types of experimental analyses of the effects of trawl gear, including an initial assessment of the “recovery” of benthic communities and habitats during this first period of zero fishing effort.

Texas coastal area targeted for surveys of benthic communities on trawled and non-trawled bottom.

During 2001, a survey was conducted to measure potential effects of the first closure of the SSZ on nearshore continental shelf habitats and benthos. The SSZ was closed on 1 December 2000 and re-opened on 1 July 2001. During 18-22 June 2001, benthos and sediment samples were collected from two areas on the northern end of Mustang Island centered on Corpus Christi Fish Pass: an SSZ block 18.5 km (10 nmi) long and 9.3 km (5 nmi) wide, and an adjoining NSZ block of the same dimensions. A GIS database was used to develop random stratified sampling sites based on sediment characteristics of each block. Sampling sites were located via vessel-mounted global positioning systems. Divers collected benthos and sediment cores from 32 sites in each block. Results from this study will be available during summer 2002. During summer and fall 2002, the SSZ and NSZ blocks will be examined by underwater videography and diver transects to determine the distribution and abundance of epibiota (soft corals such as sea pens, sea whips, and sea pansies) which can be damaged or uprooted by shrimp trawls. Beginning with the SSZ closure in December 2002, experimental trawling effort will be applied at several intensities along transects in the closed area for the duration of the closure. These transects, as well as transects receiving ambient effort in the adjoining NSZ, will be monitored for faunal changes using underwater video and diver-retrieved benthic cores. These data will constitute some of the first available for assessing impacts of shrimp trawling to essential fish habitat in the Gulf of Mexico.