DOI: 10.5061/dryad.fqz612js1
title: Data from: Regional movements of satellite-tagged whale sharks Rhincodon typus in the Gulf of Aden

description: To gain insight into whale shark (Rhincodon typus) movement patterns in
 the Western Indian Ocean, we deployed eight pop-up satellite tags at an
 aggregation site in the Arta Bay region of the Gulf of Tadjoura, Djibouti
 in the winter months of 2012, 2016 and 2017. Tags revealed movements
 ranging from local-scale around the Djibouti aggregation site, regional
 movements along the coastline of Somaliland, movements north into the Red
 Sea, and a large-scale (&gt;1000 km) movement to the east coast of
 Somalia, outside of the Gulf of Aden. Vertical movement data revealed high
 occupation of the top ten meters of the water column, diel vertical
 movement patterns and deep diving behaviour. Long-distance movements
 recorded both here and in previous studies suggest that connectivity
 between the whale sharks tagged at the Djibouti aggregation and other
 documented aggregations in the region are likely within annual timeframes.
 In addition, wide-ranging movements through multiple nations, as well as
 the high use of surface waters recorded, likely exposes whale sharks in
 this region to several anthropogenic threats, including targeted and
 bycatch fisheries and ship-strikes. Area-based management approaches
 focusing on seasonal hotspots offer a way forward in the conservation of
 whale sharks in the Western Indian Ocean. 
description: Satellite tags
 were deployed on whale sharks in the Arta Bay region of the Gulf of
 Tadjoura (11.57°N, 42.77°E; Fig. 1) in January and/or December in 2012 (n
 = 2), 2016 (n = 3) and 2017 (n = 3; Table 2). Sharks<i>
 </i>were visually located by boat-based searches from a 6 m long
 skiff with a single outboard engine and then approached slowly. Sharks
 larger than 3.5 m were targeted (1) to satisfy a minimum size for tagging
 and (2) due to the assumption that only sharks of a certain size migrated
 from the Gulf of Tadjoura study site. Free-divers entered the water from
 the vessel to tag and measure sharks, as well as take photo-ID images.
 Tags were deployed by a pole-spear with a welded plate and rubber buffer
 to prevent insertion greater than 8-10 cm. 2012 tags were leadered with a
 ~15 cm length of 45 kg nylon filament covered with several layers of heat
 shrink tubing and attached via a titanium flat anchor M dart (Wildlife
 Computers) and placed at the base of the first dorsal fin, on the left
 side. 2016 and 2017 tags were connected to a large titanium anchor
 (Wildlife Computers) via a 50 cm stainless steel tether. Tether lengths
 were selected to allow the anchor to be placed 8-10 cm below the skin and
 leave space to let the tag lie flat against the body surface in the case
 of the former, and to facilitate breaking the air-surface barrier for
 transmission during deployment for the latter. Individual sharks were
 measured (total length, TL) by one of two methods; 1) by using visual
 observation and comparing the shark to an object of known size, and/or 2)
 by an intense photogrammetric laser measurement campaign using the methods
 as described in Jeffreys et al. (2013). Photo-ID images were also taken of
 the left and right flanks of tagged individuals and matched with the
 existing Djibouti database using the public domain pattern-recognition
 software I<sup>3</sup>S (Interactive Individual Identification
 System; Van Tienhoven et al. 2007). All fieldwork was approved by, and
 conducted with the knowledge of, the Ministry of Environment, Djibouti and
 local authorities in Arta. All procedures followed standard international
 guidelines for tagging whale sharks and staff were trained by experts in
 the field (D. Rowat and M. Meekan; Wilson et al. 2006, Robinson et al.
 2017). Pop-up
 satellite archival transmitting (PSAT) tags (6 x MK10, 2 x MiniPAT;
 Wildlife Computers, Inc., WA, USA) recorded light levels, depth and
 ambient temperature and were programmed to remain attached for 100 days
 (2012), 120 days (2016) or 153 days (2017), or programmed to detach if
 recording depths greater than 1800 m or a constant depth reading (± 1.0 m)
 for more than one week. The tags recorded depth and temperature data in
 predefined bins every six hours for transmission, with depth bin size
 varying slightly between 2016 and 2017 deployments (0-2, 2-5, 5-10, 10-25,
 50-100, 100-200, 200-300, 300-400, 400-500, &gt;500 and 0-10, 10-50,
 50-100, 100-250, 250-500, &gt;500 respectively). Histogram sampling
 was offset by three hours so that depth and temperature data were
 collected for local day (6:00-12:00 and 12:00-18:00) and night
 (18:00-00:00 and 00:00-6:00) periods. The 2012 tags recorded and archived
 depth data at five-minute intervals, which were subsequently summarized
 into the 2016 bins. A Wilcoxon rank sum test was used to compare median
 day- and night-time depths for time-series data from the two 2012
 tags.  Location data
 and/or processed archived data were transmitted and retrieved through the
 Argos satellite system when the tags detached. Detachment of the tag from
 the shark was identified by a combination of near-continuous high quality
 Argos transmissions for the first few hours of each day and depth
 summaries from histograms consistent with surface records (Hearn et al.
 2013). The tags deployed in 2016 and 2017 also transmitted data when
 sharks swam at the surface, and, in addition, housed a Fastloc global
 positioning system (GPS) for acquiring location information.
  
description: Data were extracted from the raw tag data using the Wildlife
 Computers Data Analysis Program 3.0 (available at https://wildlifecomputers.com/support/downloads/). Please refer to the PDF at https://static.wildlifecomputers.com/Spreadsheet-File-Descriptions-1.pdf for more detail on each file.  Data from sharks 104072 and 104073 are provided in one file.