scholarly journals Whale Shark Aggregations in the Northern Gulf of Mexico

2013 ◽  
Author(s):  
Eric Hoffmayer ◽  
Jennifer A McKinney ◽  
James S. Franks ◽  
Jill Hendon ◽  
William B Driggers III
Keyword(s):  
Gulf Of Mexico ◽  
Whale Shark ◽  
Shelf Edge ◽  
Potential Prey ◽  
Effective Technique ◽  
Specific Location ◽  
Northern Gulf Of Mexico ◽  
Whale Sharks ◽  
Directed Research ◽  
Juvenile Males

Background: The Northern Gulf of Mexico Whale Shark Research Program was initiated in 2003 to increase our knowledge of whale shark occurrence and distribution within the region. A primary goal was to obtain sightings data from “citizen scientists” to guide directed research. Whale sharks are typically solitary animals, but are known to aggregate in areas of high prey abundance. Methods: Whale shark sightings data reported from 2003 to present were compiled. Aggregations were defined as more than one whale shark, and large aggregations were defined as 10 or more sharks, observed at a specific location at the same time. Efforts were made to encounter aggregations to determine size and sex assemblage of the sharks, and to collect plankton samples to identify potential prey. Results: To date we have over 600 whale shark sightings reports and four research encounters of large aggregations. Whale shark aggregations represented 31% of reported sightings, 25% of which were large aggregations between 10-150 individuals. All of thereported large aggregations occurred during summer, almost exclusively along the continental shelf edge, with 41% occurring at Ewing Bank. Three out of the four scientific encounters occurred at Ewing Bank (2009, 2010, 2013). Aggregations were dominated by immature males that were primarily feeding on Euthynnus alletteratus eggs. Conclusions: The use of sightings data provided by “citizen scientists” has proven to bean inexpensive and effective technique for identifying whale shark aggregation locations in the northern Gulf of Mexico. Aggregation assemblages appear to consist of largely juvenile males that were feeding on tuna eggs. Similar to other regions, it is unknown if whale sharks in the northern Gulf of Mexico primarily consist of juveniles or if juveniles simply dominate these large feeding aggregations.

scholarly journals Whale Shark Aggregations in the Northern Gulf of Mexico

2013 ◽  
Author(s):  
Eric Hoffmayer ◽  
Jennifer A McKinney ◽  
James S. Franks ◽  
Jill Hendon ◽  
William B Driggers III
Keyword(s):  
Gulf Of Mexico ◽  
Whale Shark ◽  
Shelf Edge ◽  
Potential Prey ◽  
Effective Technique ◽  
Specific Location ◽  
Northern Gulf Of Mexico ◽  
Whale Sharks ◽  
Directed Research ◽  
Juvenile Males

Background: The Northern Gulf of Mexico Whale Shark Research Program was initiated in 2003 to increase our knowledge of whale shark occurrence and distribution within the region. A primary goal was to obtain sightings data from “citizen scientists” to guide directed research. Whale sharks are typically solitary animals, but are known to aggregate in areas of high prey abundance. Methods: Whale shark sightings data reported from 2003 to present were compiled. Aggregations were defined as more than one whale shark, and large aggregations were defined as 10 or more sharks, observed at a specific location at the same time. Efforts were made to encounter aggregations to determine size and sex assemblage of the sharks, and to collect plankton samples to identify potential prey. Results: To date we have over 600 whale shark sightings reports and four research encounters of large aggregations. Whale shark aggregations represented 31% of reported sightings, 25% of which were large aggregations between 10-150 individuals. All of thereported large aggregations occurred during summer, almost exclusively along the continental shelf edge, with 41% occurring at Ewing Bank. Three out of the four scientific encounters occurred at Ewing Bank (2009, 2010, 2013). Aggregations were dominated by immature males that were primarily feeding on Euthynnus alletteratus eggs. Conclusions: The use of sightings data provided by “citizen scientists” has proven to bean inexpensive and effective technique for identifying whale shark aggregation locations in the northern Gulf of Mexico. Aggregation assemblages appear to consist of largely juvenile males that were feeding on tuna eggs. Similar to other regions, it is unknown if whale sharks in the northern Gulf of Mexico primarily consist of juveniles or if juveniles simply dominate these large feeding aggregations.

scholarly journals Seasonal habitat use of whale sharks in the northern Gulf of Mexico, USA 2003 - 2013

2013 ◽  
Author(s):  
Jennifer A McKinney ◽  
Eric R Hoffmayer ◽  
Jim S Franks ◽  
Jill M Hendon ◽  
William B Driggers
Keyword(s):  
Home Range ◽  
Gulf Of Mexico ◽  
Habitat Use ◽  
Whale Shark ◽  
Shelf Edge ◽  
Northern Gulf Of Mexico ◽  
Use Patterns ◽  
Core Habitat ◽  
Whale Sharks ◽  
Satellite Tagging

Background: Reports of whale sharks (Rhincodon typus) in the northern Gulf of Mexico (GOM) date back to the 1930s. In 2003, the Northern Gulf of Mexico Whale Shark Research Program was established and began making directed efforts to document the regional occurrence, seasonal distribution and habitat preferences of whale sharks. Methods: Whale shark sightings data (WSS: 1989 – present; n=644) and tagging geoposition data (TD: 2009-2012; n=450) were used in seasonal kernel density (KD) analyses to delineate home range (95%) and core habitat (50%) use areas in the northern GOM. Kernel density estimation of distribution is a statistically robust manner of handling data sources with differing sampling designs (anecdotal vs. directed). Habitat use patterns from the two datasets were used to identify critical use areas. Results: In the study area, whale shark home range was 276,000 km2 (WSS) to 369,000 km2 (TD) in size, with 52,000 km2 (WSS) to 62,000 km2 (TD) being core habitat. Whale shark habitat use varied seasonally, with the largest home range occurring during summer (WSS: 213,000 km2) and fall (TD: 221,000 km2). Tag data revealed more winter habitat (75,000 km2) than the sightings dataset (41,000 km2), which was shifted further offshore to slope waters. Significant use patterns occurred along the continental shelf-edge, encompassing shelf-edge banks south of Louisiana, and near the mouth of the Mississippi River. Conclusions: The combination of sightings data and satellite tagging data represents an effective methodology for assessing seasonality of occurrence, distribution, and habitat use of whale sharks. Shelf-edge bank habitats were most commonly used by whale sharks in the region. Satellite tagging data provided additional evidence of connectivity between multiple jurisdictions, which lends support for international management of the species.

scholarly journals Seasonal habitat use of whale sharks in the northern Gulf of Mexico, USA 2003 - 2013

2013 ◽  
Author(s):  
Jennifer A McKinney ◽  
Eric R Hoffmayer ◽  
Jim S Franks ◽  
Jill M Hendon ◽  
William B Driggers
Keyword(s):  
Home Range ◽  
Gulf Of Mexico ◽  
Habitat Use ◽  
Whale Shark ◽  
Shelf Edge ◽  
Northern Gulf Of Mexico ◽  
Use Patterns ◽  
Core Habitat ◽  
Whale Sharks ◽  
Satellite Tagging

Background: Reports of whale sharks (Rhincodon typus) in the northern Gulf of Mexico (GOM) date back to the 1930s. In 2003, the Northern Gulf of Mexico Whale Shark Research Program was established and began making directed efforts to document the regional occurrence, seasonal distribution and habitat preferences of whale sharks. Methods: Whale shark sightings data (WSS: 1989 – present; n=644) and tagging geoposition data (TD: 2009-2012; n=450) were used in seasonal kernel density (KD) analyses to delineate home range (95%) and core habitat (50%) use areas in the northern GOM. Kernel density estimation of distribution is a statistically robust manner of handling data sources with differing sampling designs (anecdotal vs. directed). Habitat use patterns from the two datasets were used to identify critical use areas. Results: In the study area, whale shark home range was 276,000 km2 (WSS) to 369,000 km2 (TD) in size, with 52,000 km2 (WSS) to 62,000 km2 (TD) being core habitat. Whale shark habitat use varied seasonally, with the largest home range occurring during summer (WSS: 213,000 km2) and fall (TD: 221,000 km2). Tag data revealed more winter habitat (75,000 km2) than the sightings dataset (41,000 km2), which was shifted further offshore to slope waters. Significant use patterns occurred along the continental shelf-edge, encompassing shelf-edge banks south of Louisiana, and near the mouth of the Mississippi River. Conclusions: The combination of sightings data and satellite tagging data represents an effective methodology for assessing seasonality of occurrence, distribution, and habitat use of whale sharks. Shelf-edge bank habitats were most commonly used by whale sharks in the region. Satellite tagging data provided additional evidence of connectivity between multiple jurisdictions, which lends support for international management of the species.

scholarly journals Seasonal Occurrence, Horizontal Movements, and Habitat Use Patterns of Whale Sharks (Rhincodon typus) in the Gulf of Mexico

2021 ◽  
Vol 7 ◽  
Author(s):  
Eric R. Hoffmayer ◽  
Jennifer A. McKinney ◽  
James S. Franks ◽  
Jill M. Hendon ◽  
William B. Driggers ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Habitat Use ◽  
Continental Shelf ◽  
Site Fidelity ◽  
Seasonal Occurrence ◽  
Whale Shark ◽  
Shelf Edge ◽  
Rhincodon Typus ◽  
Aggregation Site ◽  
Whale Sharks

In the northern Gulf of Mexico (GOM), whale sharks (Rhincodon typus) form large aggregations at continental shelf-edge banks during summer; however, knowledge of movements once they leave aggregation sites is limited. Here we report on the seasonal occurrence of whale sharks in the northern GOM based on over 800 whale shark sightings from 1989 to 2016, as well as the movements of 42 whale sharks tagged with satellite-linked and popup satellite archival transmitting tags from 2008 to 2015. Sightings data were most numerous during summer and fall often with aggregations of individuals reported along the continental shelf break. Most sharks (66%) were tagged during this time at Ewing Bank, a known aggregation site off the coast of Louisiana. Whale shark track duration ranged from three to 366 days and all tagged individuals, which ranged from 4.5 to 12.0 m in total length, remained within the GOM. Sightings data revealed that whale sharks occurred primarily in continental shelf and shelf-edge waters (81%) whereas tag data revealed the sharks primarily inhabited continental slope and open ocean waters (91%) of the GOM. Much of their time spent in open ocean waters was associated with the edge of the Loop Current and associated mesoscale eddies. During cooler months, there was a net movement southward, corresponding with the time of reduced sighting reports. Several sharks migrated to the southwest GOM during fall and winter, suggesting this region could be important overwintering habitat and possibly represents another seasonal aggregation site. The three long-term tracked whale sharks exhibited interannual site fidelity, returning one year later to the vicinity where they were originally tagged. The increased habitat use of north central GOM waters by whale sharks as summer foraging grounds and potential interannual site fidelity to Ewing Bank demonstrate the importance of this region for this species.

Cephalopods in the potential prey field of sperm whales (Physeter macrocephalus) (Cetacea: Physeteridae) in the northern Gulf of Mexico

2013 ◽  
Vol 49 (21-24) ◽  
pp. 1267-1280 ◽  
Author(s):  
Heather Judkins ◽  
Scarlett Arbuckle ◽  
Michael Vecchione ◽  
Lance Garrison ◽  
Anthony Martinez
Keyword(s):  
Gulf Of Mexico ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Potential Prey ◽  
Northern Gulf Of Mexico

scholarly journals Oceanographic influences on a global whale shark hotspot in southern Mozambique

2014 ◽  
Author(s):  
Christoph A Rohner ◽  
Scarla J Weeks ◽  
Anthony J Richardson ◽  
Simon J Pierce ◽  
Marites M Magno-Canto ◽  
...  
Keyword(s):  
Time Series ◽  
Coastal Waters ◽  
Prey Availability ◽  
Sea Surface ◽  
Height Anomaly ◽  
Coastal Current ◽  
Whale Shark ◽  
Shelf Edge ◽  
Upwelled Water ◽  
Whale Sharks

Coastal aggregations of whale sharks Rhincodon typus around the world are generally seasonal and driven by prey availability. At a major aggregation site in southern Mozambique, whale sharks are, somewhat unusually, present and seen feeding throughout the year. We investigated potential oceanographic mechanisms that may regulate prey availability on the narrow regional shelf and hence account for this year-round whale shark hotspot. We used regional aerial surveys to show that the highest density of whale sharks (29 sharks 100 km-1) was near Praia do Tofo (23.85˚S, 35.55˚E). To investigate how the regional oceanography influences the enrichment of shelf waters, we used 5- and 9-year time series of hourly underwater temperature, and 10-year time series of remotely-sensed sea surface temperature, chlorophyll-a concentration and sea surface height anomaly data. We found that upwelling of cool, nutrient-rich water was common in the region throughout the year and describe three mechanisms, all of which are likely to stimulate productivity: (1) Shelf-edge upwelling and subsequent elevated plankton biomass in coastal waters north of Praia do Tofo, driven by the interaction of southward-propagating mesoscale eddies with the narrow shelf. In situ temperature data show that this interaction frequently leads to intense upwelling, up to 7.5˚C daily amplitude, throughout the year, but is most pronounced in spring/summer. (2) Divergent upwelling south of Praia do Tofo driven by the current flow along the shelf edge as it diverges from the coastline. This upwelling can occur throughout the year and is similar in intensity, but less frequent, than the shelf-edge upwelling. (3) Vortex-driven upwelling by the Delagoa Bight lee-eddy, which may increase phytoplankton biomass in the Bight and also force a northward coastal current that transports recently-upwelled water towards Praia do Tofo. We hypothesise that whale sharks aggregate in coastal waters around Praia do Tofo throughout the year because these upwelling mechanisms contribute to year-round productivity in the region.

scholarly journals Oceanographic influences on a global whale shark hotspot in southern Mozambique

2014 ◽  
Author(s):  
Christoph A Rohner ◽  
Scarla J Weeks ◽  
Anthony J Richardson ◽  
Simon J Pierce ◽  
Marites M Magno-Canto ◽  
...  
Keyword(s):  
Time Series ◽  
Coastal Waters ◽  
Prey Availability ◽  
Sea Surface ◽  
Height Anomaly ◽  
Coastal Current ◽  
Whale Shark ◽  
Shelf Edge ◽  
Upwelled Water ◽  
Whale Sharks

Coastal aggregations of whale sharks Rhincodon typus around the world are generally seasonal and driven by prey availability. At a major aggregation site in southern Mozambique, whale sharks are, somewhat unusually, present and seen feeding throughout the year. We investigated potential oceanographic mechanisms that may regulate prey availability on the narrow regional shelf and hence account for this year-round whale shark hotspot. We used regional aerial surveys to show that the highest density of whale sharks (29 sharks 100 km-1) was near Praia do Tofo (23.85˚S, 35.55˚E). To investigate how the regional oceanography influences the enrichment of shelf waters, we used 5- and 9-year time series of hourly underwater temperature, and 10-year time series of remotely-sensed sea surface temperature, chlorophyll-a concentration and sea surface height anomaly data. We found that upwelling of cool, nutrient-rich water was common in the region throughout the year and describe three mechanisms, all of which are likely to stimulate productivity: (1) Shelf-edge upwelling and subsequent elevated plankton biomass in coastal waters north of Praia do Tofo, driven by the interaction of southward-propagating mesoscale eddies with the narrow shelf. In situ temperature data show that this interaction frequently leads to intense upwelling, up to 7.5˚C daily amplitude, throughout the year, but is most pronounced in spring/summer. (2) Divergent upwelling south of Praia do Tofo driven by the current flow along the shelf edge as it diverges from the coastline. This upwelling can occur throughout the year and is similar in intensity, but less frequent, than the shelf-edge upwelling. (3) Vortex-driven upwelling by the Delagoa Bight lee-eddy, which may increase phytoplankton biomass in the Bight and also force a northward coastal current that transports recently-upwelled water towards Praia do Tofo. We hypothesise that whale sharks aggregate in coastal waters around Praia do Tofo throughout the year because these upwelling mechanisms contribute to year-round productivity in the region.

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