Virginia and Maryland Sea Turtle Research and Conservation Initiative Aerial Survey Sightings, May 2011 through July 2013

Virginia Aquarium Foundation - Susan G. Barco & Gwen G. Lockhart
Riverhead Foundation for Marine Research & Preservation - Robert A. DiGiovanni Jr. & Allison M. DePerte

The data provided were collected as part of the the Virginia and Maryland Sea Turtle Research & Conservation Initiative - funded by the National Marine Fisheries Service Species Recovery Grants program No. NA09NMF4720033.

Previous sea turtle abundance estimates reported in the Virginia portion of the Chesapeake Bay where developed using aerial surveys without correcting for seasonal differences and availability bias. More recent surveys yielded estimates of availability throughout the turtles' residency periods using radio transmitters and satellite telemetry. These estimates where significantly different then previous surveys and changed over time. This project was conducted in order to quantify turtles surfacing time for the purpose of calculating seasonal and annual differences in availability, conduct aerial surveys in a manner that will allow for the calculation of perception bias, and compare estimates generated during previous projects.

Aerial surveys were conducted along the coastal waters and bays of Virginia and Maryland. This project is broken into two survey periods. The survey platform was a De Havilland twin otter DHC‐6 modified for observational research. The aircraft was configured so as to have two forward observers and a data recorder on their own communication system and have a second team consisting of a belly observer and one additional observer (either port or starboard) along with a data recorder. The separation of the communications systems enables the two teams to function independently thereby functioning as two individual surveys. Groups of sea turles, marine mammals, and other marine mammals were recorded. This method was developed in order to calculate a perception bias using mark recapture techniques. This dataset is the filtered version – meaning all the duplicate sightings have been removed. All records are marked as observed by only team one, only team two, or by both. There is only one record for each sighting even if the animal was sighted by both teams. The raw dataset, with all sighting from both teams, is available by request from the Virginia Aquarium & Marine Science Foundation.

Overview

This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)	Description
oid	Unique ID number (generated by OBIS-SEAMAP)
objectid	Row ID assigned by VAQF ArcGIS
obs_count	Best estimate of group size
obs_date	Date of sighting
obs_time	Time of sighting in local time zone
sp_obs	Species name recorded
sp_tsn	Taxonomic Serial Number added by OBIS-SEAMAP
strata	Survey block: A to E
survey	Number of survey
transect	Recorded transect line: Series/LineNumber
series	Set of lines used during survey
linenumber	Number of transect line
team	Observer team: 1 = front, 2 = rear, 3 = both
line	Line ID
sightingnumber	Sighting number as recorded
duplicatesightingnumber	Recorded sighting number of duplicate sighting
obs	Initials of observer
angside	Side of sighting: R = right, L = left (only recorded if ObsPosition = C)
dist_m	Perpendicular distance (meters)
swimdir	Swim direction
obsposition	Position of observer in plane: L = left, R = right, C = centre (belly window)
latitude	Latitude in decimal degrees
longitude	Longitude in decimal degrees
speed	Speed of plane
direction	Direction of plane (degrees)
altitude	Altitude of plane (meters)
beaufort	Beaufort sea state
turbidity	Turbidity: 0 = clear, 1 = moderately clear, 2 = turbid, 9 = unknown
cc	Cloud cover: 0 = no clouds, 1-99 = %age of cloud cover
glarefrom	Glare from front of plane
glareto	Glare to front of plane
glareseverity	Severity of glare: 0 = none, 1 = slight, 2 = moderate, 3 = excessive
quality	Subjective quality: 1 = excellent, 2 = good, 3 = moderate, 4 = fair, 5 = poor, 0 = over land or off effort
transectid	Transect identifier based on Survey-LineNumber
sightingid	Unique identifier of sighting: Survey-Team-SightingNum
dupid	Unique identifier of duplicate sighting
speciesgroup	Species group of sighting
transect_label	TransectLabel Transect identifier based on Season-Year-LineNumber
ang	Angle from horizon
newteam	Observer team: 1 = front, 2 = rear, 3 = both
transectetid	Transect identifier based on TransectYearMonthDay
sst_c	Sea surface temperature (Celsius)
sst_f	Sea surface temperature (Fahrenheit)
geom	Geometry field added by OBIS-SEAMAP