Utila Whale Shark Research

Utila, Honduras

Utila Whale Shark Research

Utila, Honduras
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Hoffmayer E.R.,National Oceanic and Atmospheric Administration | Holmberg J.,Wild Me | Graham R.T.,MarAlliance | Driggers W.B.,National Oceanic and Atmospheric Administration | And 6 more authors.
PLoS ONE | Year: 2017

The predictable occurrence of whale sharks, Rhincodon typus, has been well documented in several areas. However, information relating to their migratory patterns, residency times and connectivity across broad spatial scales is limited. In the present study photo-identification data is used to describe whale shark population structure and connectivity among known aggregation sites within the Western Central Atlantic Ocean (WCA). From 1999 to 2015, 1,361 individuals were identified from four distinct areas: the Yucatan Peninsula, Mexico (n = 1,115); Honduras (n = 146); northern Gulf of Mexico, United States (n = 112), and Belize (n = 49). Seasonal patterns in whale shark occurrence were evident with encounters occurring in the western Caribbean Sea earlier in the year than in the GOM. There was also a significant sex bias with 2.6 times more males present than females. Seventy sharks were observed in more than one area and the highest degree of connectivity occurred among three aggregation sites along the Mesoamerican Reef. Despite this, the majority of resightings occurred in the area where the respective sharks were first identified. This was true for the WCA as a whole, with the exception of Belize. Site fidelity was highest in Mexico. Maximum likelihood modelling resulted in a population estimate of 2,167 (95% c.i. 1585.21–2909.86) sharks throughout the entire region. This study is the first attempt to provide a broad, regional population estimate using photo-identification data from multiple whale shark aggregations. Our aim is to provide population metrics, along with the description of region-scale connectivity, that will help guide conservation action in the WCA. At a global level, rapidly growing photographic databases are allowing for researchers to look beyond the description of single aggregation sites and into the ocean-scale ecology of this pelagic species.


Fox S.,Utila Whale Shark Research | Foisy I.,Utila Whale Shark Research | De La Parra Venegas R.,Chooj Ajauil AC | Galvan Pastoriza B.E.,Chooj Ajauil AC | And 5 more authors.
Journal of Fish Biology | Year: 2013

There were 479 reported whale shark Rhincodon typus encounters between 1999 and 2011 at the island of Utila, which forms part of the Meso-American Barrier Reef System (MBRS) in the western Caribbean Sea. The majority of R. typus were found to feed on small bait fish associated with various tuna species. Ninety-five individual R. typus, ranging from 2 to 11m total length (LT), were identified through their unique spot patterns. A significant male bias (65%) was present. There was no significant difference between the mean±s.d. LT of female (6·66±1·65m) and male (6·25±1·60m) R. typus. Most R. typus were transient to Utila, with 78% sighted only within a single calendar year, although some individuals were sighted in up to 5years. Mean residency time was modelled to be 11·76days using maximum likelihood methods. © 2013 The Fisheries Society of the British Isles.

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