Abstract:
The dataset contains distribution and abundance data for rays in the Gulf of Mexico collected through aerial surveys and satellite telemetry. Aerial survey data includes the date, time, latitude and longitude where rays were observed, and number and species of rays observed during 32 surveys which took place from 2008 to 2011. Satellite telemetry data contains data for 11 cownose rays that were fitted with Smart Positioning or Temperature satellite transmitters between March and November 2011. The satellite telemetry data includes information about the cownose rays that were tracked, including the location they were caught, disk length, disk width, weight, sex, the number of days that the satellite tag remained attached to the ray, the calculated total distance traveled by each ray while fitted with the tag, and the calculated mean and maximum rate of movement for each ray while fitted with the satellite tag. The data from ARGOS that was used to calculate total distance and rates of movement for the tagged cownose rays is included in this data set and includes location date, satellite that received the signal, latitude, longitude, number of messages received and data ARGOS used to calculate the error ellipse for each location.
Suggested Citation:
Ajemian, Matthew, and Sean Powers. 2014. Fine-scale Ray habitat use, distribution and abundance, satellite telemetry and aerial survey, Northern Gulf of Mexico, 2008 to 2012. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7PN93KF
Purpose:
To assess potential impacts of DWH incident on rays by comparing distribution and abundance of rays from aerial surveys in completed in 2008-2009 with those completed in 2010-2011 and to delineate fine scale habitat use and movement patterns of cownose rays in the Gulf of Mexico using satellite telemetry.
Data Parameters and Units:
{Excel File: MAjemian_BP_SGER_aerial _survey_data_rays.xlsx [Survey Design Worksheet.] PROJECT: project for which the survey was funded; YEAR: year; MONTH: Month where 1 = January and 12 = December; DATE: MM/DD/YYYY; ROUTE: designates the three separate routes used in each survey see supplementary material for more information; TRANSECTS: the number of North-South transects flown and their distance in nautical miles; DISTANCE: total distance of transects flown in nautical miles; WEATHER: General weather conditions if reported; ANGLE?: Angle (in degrees) over with observer scanned from viewing window on aircraft; ALTITUDE1: Altitude (feet) of the aircraft from which the aerial survey was completed; SWATH_MI: Swath of observer sighting coverage in miles; SWATH_KM: Swath of observer sighting in coverage in kilometers; SWATH_NM: Swath of observer sighting coverage in nautical miles. [Transects Tables Worksheet.] Date: MM/DD/YYYY; ROUTE: designates the three separate routes used in each survey see supplementary material for more information; Transect: the transect that the observation took place on; ID: Unique ID generated by combining Julian Date and transect number; Length (mi): Length of transect in miles; Length (km): Length of transect in kilometers; Altitude (ft): Altitude (feet) of the aircraft from which the aerial survey was complete; Swath (mi): swath of observer sighting coverage in miles; Swath (km) swath of observer sighting coverage in kilometers; Area (sqmi): Area covered by transect in square miles; Area (sqkm): Area covered by transect in square kilometers;: [Observations Worksheet.] Time: PROJECT: project for which the survey was funded; YEAR: year; MONTH: Month where 1 = January and 12 = December; DATE: MM/DD/YYYY; TIME: ROUTE: designates the three separate routes used in each survey see supplementary material; TRANSECT: the Transect that the observation took place on; TIME: 24 – Hour Military Time; SPECIES: Species of Ray Observed; COUNT: Count of individuals for the species at the given time and space; COUNT1: Count of individuals by given time and space and default value of 1 when no value was given for an actual count; COUNTCODE: Binary text code given to data to indicate whether a count was actually given (COUNT) or if a count was not given and a default value of 1 was used (DEFAULT); LAT: Latitude in Decimal Degrees; LONG: Longitude in Decimal Degrees; DEPTH_M: Bottom depth of water (in meters) at sighting location of rays} {Excel File: MAjemian_BP-SGER_SatelliteData.xlsx [TagTable Worksheet] AnimalID: Animal identification number represents the Nth deployment of a SPOT5 transmitter, 4 attempts made in previous studies therefore starts at the 5th deployment; Species: CNR = cownose ray; Tag Date: MM/DD/YYYY; Season: SP = spring, SU = summer, F = fall; Location: Generalized Descriptive Location along Alabama coast where the animal was caught, where PB = Pelican Bay, WEDI = West End of Dauphin Island, PI-FB = Pelican Island Front Beach, Public Beach = Public Beach at Dauphin Island, KC-FB = Katrina Cut Front Beach between west and east ends of Dauphin Island, Perdido = Perdido Beach on the Alabama-Florida border; DW: Disk Width, the distance between pectoral fin (wing) tips measured ventrally in millimeters from the animal laid flat on a measuring board; DL: Disk Length, the distance from snout to cloaca measured in millimeters from the animal laid flat on a measuring board; W: weight in kilograms; Sex: M= Male, F=Female; PTT ID: Platform Transmitter Terminal equivalent to transmitter ID; External Tag ID: External tag identification number; LAT: Latitude of the release location of the animal after SPOT5 attached in decimal degrees; LON: Longitude of the release location of the animal after SPOT5 attached in decimal degrees; Est. Detach Date: Date (MM/DD/YYYY) which SPOT5 tag was determine to have detached from the animal; Days at Liberty: Time (days) between release and estimated tag detach date; Total Distance: Cumulative Sum of step lengths (distance between successive position estimates) for position that had location class of 1 to 3 where location class is an estimation of location accuracy where 3 is the most accurate (±250 meters) and 1 is the least accurate (± 500 to 1500 meters); Mean ROM: Rate of Movement ( total distance traveled/number of days at liberty) in kilometers per day; Max ROM: Maximum rate of movement, the maximum rate at which the ray moved between two successive position estimates in kilometers per day; Total Distance: Mean daily Sum of step lengths (distance between successive position estimates) for position that had location class of 1 to 3 where location class is an estimation of location accuracy where 3 is the most accurate (±250 meters ) and 1 is the least accurate (± 500 to 1500 meters); [Tag Data worksheet] PTT: Platform Transmitter Terminal equivalent to transmitter ID; Satellite: Satellite used to detect PTT where MB= METOP-B, NM = NOAA-N’, MA=METOP-A, NN=NOAA-19, NM = NOAA-17, NL=NOAA-16 and NK=NOAA-15; Location date: location date and time of signal in GMT, MM/DD/YYYY; Location class: an estimation of location accuracy where 3 is the most accurate (±250 meters ) and 1 is the least accurate (± 500 to 1500 meters); Latitude: In decimal degrees; Longitude: In decimal degrees; Number of messages: Number of messages received from the SPOT5 to the PTT at location and time; Nbr of messages >-120 dB: Number of messages received from the SPOT5 tag to the PTT greater than -120 decibels; Best Level: The best signal strength, ARGOS DIAG format file, in decibels; Pass Duration: duration of the satellite pass over the PTT in minutes; Error Radius: error associated with the position estimate in meters in the shape of an ellipse; Semi-major axis: Length in meters of the semi major axis of the position error ellipse; Semi-minor axis: Length in meters of the semi minor axis of the position error ellipse; Ellipse orientation: expressed as an angle with the North going towards the East, the orientation of the error ellipse; GDOP: the Geometric dilution of precision is a measure of the effect of the geometry of the satellite beacon configuration on location accuracy, as a general rule a smaller value yields a more accurate position; Message date: date the message was received via satellite.
Methods:
A. Aerial Survey Data Sets Dauphin Island Sea Lab Red Drum Aerial Survey (2008-2010) Red Drum Aerial Survey: Aerial transect surveys were conducted with a Piper Apache PA-23 aircraft. The design covered the northern central Gulf of Mexico from the shoreline to 20 nmi south (29°51′N) on eastern transects and out to 60 nmi south (29°19′N) on western transects to cover the Chandeleur Islands. The longitudinal coverage extended from the Chandeleur Islands in the west (88°59′W) to Pensacola, FL, in the east (87°19′W) (13 surveys). Two observers wearing polarized sunglasses conducted the survey by scanning the water to identify organisms from an average altitude of ~213m. When fish were spotted, the observer singled to the pilot to circle the object to confirm species identification, record GPS location, and take photographs of the fish school. These aerial surveys lasted approximately 8 hours and were conducted in two 4-hr flights with a fuel stop in between flights. (from Powers et al., 2012. Age composition and distribution of red drum (Sciaenops ocellatus) in offshore waters of the north central Gulf of Mexico: an evaluation of a stock under a federal harvest moratorium. Fish. Bull. 110: 283-292.) Dauphin Island Sea Lab Sargassum Aerial Survey (2010-2012) Sargassum Aerial Survey: These are strip-transect aerial surveys. Ten equally spaced transects were established (the 9th transect in the eastern section was dropped during the project due to time constraints). Each transect started at the shoreline and extended perpendicularly to approximately 100 km offshore. Ten aerial surveys (5/28, 6/4, 6/9, 6/16, 6/23, 7/14, 7/21, 8/18, 9/8, 10/20) were conducted after the DWH in 2010. Follow up flights were also flown in 2011 (7 flights, 7/22, 7/26, 8/17, 9/9, 9/15, 9/21, 9/28). A twin prop Piper Geronimo was used for each flight and flown between 215–300 m elevation depending on ceiling restrictions imposed by the unified command and Federal Aviation Administration (FAA) during the DWH explosion. Surveys were conducted on days where sea state was equal to or less than 4 on the Beaufort wind force scale. Two observers were seated in the rear of the aircraft and recorded the latitude and longitude (via GPS) of targets within 85° under the plane wing. The altitude for each aerial survey varied according to changing FAA restrictions; therefore, the detectable area ranged from 2.44–3.48 km, depending on the flight altitude. (from: Powers et al. 2013. Novel pathways for injury from offshore oil spills: Direct, sublethal and indirect effects of the Deepwater Horizon oil spill on pelagic Sargassum communities. PLoS ONE 8(9).) Analyses of aerial surveys included: 1) before and after DWH incident densities 2) before and after DWH incident distribution 3) Associations of rays with oil/gas platforms B. Satellite Telemetry Satellite linked radio transmitters (platform transmitter terminals or PTTs) were used to monitor the geographic movements of 11 cownose rays in the Gulf of Mexico in 2011 and 2012. Transmission from PTTs were detected and processed by the ARGOS Data Collection and Location System (ARGOS DCLS). Wildlife Computers Smart Positioning or Temperature (SPOT) 5 tags were used to transmit animal location at the surface to orbiting ARGOS satellites. Due to detachment issues in the past, we attempted to tether the SPOT5 tags to the rays using a variety of attachment techniques. The first was a modification of a monofilament suture around the ray’s tail, which proved to retain for at least 30 days in previous captive experiments. To increase the strength of the suture, we substituted monofilament with braided stainless steel wire and passed this material through a polyethylene tube. The suture was then crimped to a stainless steel sleeve above the tail anterior to the dorsal fin and covered with shrink tubing to prevent any frayed wire from contacting the ray’s skin. Despite our efforts to increase tag retention with tail sutures, rays only retained tags using this technique from 1 – 7 d. Fortunately, the detached tags were recovered by beachgoers and returned to the DISL for further deployments. One tag had shown signs of detachment via the entire suture being pulled out while another showed failure at the double-barrel swivel (supplied by the manufacturer) connecting the suture to the tag tether. To increase track time it was then decided to attempt previous techniques (i.e. double-dart bridles) which have shown a range of retention from 17 – 155 d. Moreover, a stronger 700 lb test swivel (SPRO, Inc.) was added to prevent detachment at this location. However, rays fitted with tags using double-darts still detached early and were estimated to retain their tags from 1 – 16 d. Three additional individuals were tagged in November 2011 with a spiralcular harness technique, which appeared to increase retention time.
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