Study first to show tiger sharks' travels and desired hangouts in the
Gulf of Mexico
Using satellite telemetry, FAU Harbor Branch scientist and team document
core habitat use

Date:
July 15, 2020
Source:
Florida Atlantic University
Summary:
From 2010 to 2018, scientists tagged 56 tiger sharks of varying life
stages to track their movements via satellite. Movement patterns
varied by life stage, sex, and season. Some of their core habitats
overlapped with locations designated by NOAA as Habitat Areas
of Particular Concern and also were found near 2,504 oil and gas
platforms. Findings may help inform studies into potential climate
change, oil spills, and other environmental impacts on tiger shark
movement in the Gulf of Mexico.



FULL STORY ==========================================================================
Like other highly migratory sharks, tiger sharks (Galeocerdo cuvier)
often traverse regional, national and international boundaries where they encounter various environmental and humanmade stressors. Their range
and habitat use in the Gulf of Mexico, a complex marine environment significantly impacted by the Deepwater Horizon Oil Spill in 2010,
has been understudied and remains unknown.


========================================================================== Using sophisticated satellite telemetry, a study is the first to provide
unique insights into how tiger sharks move and use habitats in the Gulf
of Mexico across life-stages. Data from the study, just published in
PLOS ONE, provide an important baseline for comparison against, and/or predicting their vulnerability to future environmental change such as
climate variability or oil spills.

For the study, Matt Ajemian, Ph.D., lead author and an assistant research professor at Florida Atlantic University's Harbor Branch Oceanographic Institute, and a team of scientists examined size and sex-related movement
and distribution patterns of tiger sharks in the Gulf of Mexico. They
fitted 56 tiger sharks with Smart Position and temperature transmitting
tags between 2010 -- following the Deepwater Horizon Oil Spill -- and
2018 -- spanning shelf waters from south Texas to south Florida and
examined seasonal and spatial distribution patterns across the Gulf of
Mexico. The tags transmitted whenever the fin-mounted tags broke the
sea surface, with orbiting satellites estimating shark positions based
on these transmissions. Ajemian also analyzed overlap of core habitats
among individuals relative to large benthic features including oil and
gas platforms, natural banks, and bathymetric breaks.

"While all life stages of tiger sharks are known to occur in the
Gulf of Mexico, detailed habitat use has never been quantified,"
said Ajemian. "This is rather striking as this marine system faces
numerous humanmade stressors, complex tri-national management,
and indications of size reductions in recreational landings for
large sharks." Results showed significant ontogenetic and seasonal
differences in distribution patterns as well as across-shelf (i.e.,
regional) and sex-linked variability in movement rates. Prior studies
into tiger shark horizontal movements in the western North Atlantic
Ocean have been restricted primarily to males or females separately, in disparate locations. By simultaneously tracking many males and females
of varying life stages within the same region, the researchers observed
sex and size-specific differences in distribution and movement rates,
as well as associations with large-scale habitat features. For example, researchers found evidence of tiger shark core regions encompassing
the National Oceanographic and Atmospheric Administration designated
Habitat Areas of Particular Concern during cooler months, particularly
by females. These are specifically bottom features of the Gulf that
rise up from the edges of the continental shelf, and include places
like the Flower Garden Banks National Marine Sanctuary. Additionally,
shark core regions intersected with 2,504 oil and gas platforms, where
previous researchers have observed them along the bottom.

The scientists note that future research may benefit from combining
alternative tracking tools, such as acoustic telemetry and genetic
approaches, which can facilitate long-term assessment of tiger shark
movement dynamics and help identify the role of the core habitats
identified in this study.

"This research is just a first glimpse into how these iconic predators
use the Gulf of Mexico's large marine ecosystem," said Ajemian.


========================================================================== Story Source: Materials provided by Florida_Atlantic_University. Original written by Gisele Galoustian. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Matthew J. Ajemian, J. Marcus Drymon, Neil Hammerschlag, R. J. David
Wells, Garrett Street, Brett Falterman, Jennifer A. McKinney,
William B.

Driggers, Eric R. Hoffmayer, Christopher Fischer, Gregory W. Stunz.

Movement patterns and habitat use of tiger sharks (Galeocerdo
cuvier) across ontogeny in the Gulf of Mexico. PLOS ONE, 2020; 15
(7): e0234868 DOI: 10.1371/journal.pone.0234868 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200715142333.htm

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