Layer: SEAMAP_Trawl_Stations (ID: 0)

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Description: Southeast Area Monitoring and Assessment Program (SEAMAP) Summer and Fall Groundfish Surveys (1987 - 2018) 40 foot trawls with 1.63 inch mesh are used to map the distribution of stations at which trawls were taken. The summer and fall surveys were established respectively in 1982 and 1985 to assess the seasonal, spatial and inter-annual variation in abundance of benthic fauna, determine population size/age structures of collected fauna and quantify associated environmental data. Under the auspices of SEAMAP, the surveys are/were completed through a cooperative effort by the National Marine Fisheries Service (NMFS), Southeast Fisheries Science Center (SEFSC) and the states of Texas (TX), Louisiana (LA), Mississippi (MS), Alabama (AL) and Florida (FL). Data collected during these surveys provide critical fishery-independent indices of relative abundance, estimates of bycatch and life history information for many species identified under Federal Fishery Management Plans. Spatial coverage of the surveys initially ranged from Brownsville, TX to Mobile Bay, AL in waters from 9 to 110 m (5 to 60 fm) with sampling conducted by NMFS, TX, LA, MS and AL. In 2007, SEAMAP received supplemental funding that allowed FL in 2008 to begin experimental bottom trawl surveys over the West Florida Shelf. Based on the success of the FL trawl program,SEAMAP surveys were expanded GOM-wide in 2010 to include the area from Mobile Bay, AL to Key West, FL. SEAMAP standard trawl operations conducted by NMFS, LA, MS, AL and FL utilize a 12.8 m (42 ft) semi-balloon trawl towed at 2.5 kt. Research permit exemptions do not require trawls to be equipped with either turtle excluder devices (TEDs) or bycatch reduction devices (BRDs). Trawl operations conducted by TX utilize a 6.1 m (20 ft) trawl. Trawl operation codes are assigned to tows that are aborted or experience irregularities during operations. All species of fishes and invertebrates from trawls are identified, enumerated, and weighed. The majority of trawl operations conducted during the summer and fall surveys by NMFS, LA, MS and AL were unified under a common sample design in 1987. Trawl stations were allocated by a stratified random design in 23 depth strata (5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, 20-22, 22-25, 25-30, 30-35, 35-40, 40-45, 45-50 and 50-60 fathoms), 5 combined statistical zones (between 88° and 97° W longitude, statistical zones from west to east: 21-20, 19-18, 17-16, 15-13 and 12-10) and 2 strata based on time of day (i.e. day or night). Trawls were towed perpendicularly to the depth contours and cover the entire depth stratum at each station. Single tows were for a maximum of 55 minutes; for some stations, a series of consecutive tows were necessary to cover a given depth stratum, with a minimum individual tow across each stratum of 10 minutes and a maximum tow of 55 minutes.In the fall of 2008, NMFS changed their method of selecting sampling sites. The states adopted this change beginning in 2010. Stations are now randomized within shrimp statistical zones and effort weighted by the spatial area of the statistical zone. Tows were standardized to 30 minutes and the day/night stratification dropped. In 2013, the sample design was further modified to include a depth stratification of 5 - 20 fathoms and 20 – 60 fathoms and sampling effort weighted by the spatial area of each statistical zone and depth stratification. Trawl operation conducted by TX were not incorporated into the unified sampling design due to differences in station selection and the use of a non-standard SEAMAP trawl. In October 2014, SEAMAP decided to no longer fund TX trawling efforts. However, TX trawl surveys are still conducted as part Texas Parks and Wildlife marine resource monitoring programs.Trawl operation, effort and catch information were extracted from the Gulf States Marine Fisheries Commission (GSMFC) SEAMAP Database (public_SEAMAP.zip Version 05-13-2019) obtained from their online SEAMAP access portal (Gulf States Marine Fisheries SEAMAP Online Access). Trawl operations conducted during the SEAMAP Summer and Fall Shrimp/Groundfish Surveys by NMFS, LA, MS, AL and FL from 1987 to 2018 without operation codes indicating irregularities during operations were extracted for analysis. In cases where multiple tows were needed to cover a depth stratum in the original unified design, only the first tow is utilized for this analysis. Trawls not taken as part of the unified sampling design or during special projects were also eliminated. Locations of trawls are used to map the distribution station at which sampling occurred.

Copyright Text: David Hanisko, Research Fisheries Biologist, National Marine Fisheries Service, Jeff Rester, SEAMAP Coordinator, Gulf States Marine Fisheries Commission, Adam Pollack, Fisheries Biologist III, Riverside Technology, Inc. National Marine Fisheries Service

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LON ( type: esriFieldTypeDouble, alias: LON )
LAT ( type: esriFieldTypeDouble, alias: LAT )
SURVEY ( type: esriFieldTypeString, alias: SURVEY, length: 254 )
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