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Great White Sharks (Carcharodon carcharias) play an important
role in the ocean ecosystem. They help maintain the food web as an apex predator. Although White Sharks aren’t endangered, they are
listed as vulnerable. Understanding where White Shark nurseries are located
allows for fisheries managers and government agencies to protect the young
sharks from unintended bycatch. Scientists know very little about the migration routes of White Sharks,
which makes it difficult to locate the exact location of these shark nurseries.
There are very few known locations of these nurseries, such as off the coast of California
and Mexico. However, with the expansion of research technology, scientists are
able to satellite tag White Sharks and follow their migratory routes. This
tagging technology has allowed researchers to discovered new White Shark nurseries
along the coast of New York. Gaining a fuller understanding of these nurseries
will allow for stronger conservation efforts for White Sharks.
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| Great White Shark. Photo by Elias Levy. Creative Commons Flickr |
Shark nurseries are historically
defined as regions where young are born or reside as they grow towards
maturity. Based on data that is available, scientists have come up with three
criteria that must be met for an area to be called a shark nursery: (1) sharks
are more commonly discovered in the area than other areas; (2) sharks remain in
the area or return for extended periods; and (3) the area is repeatedly used
across years (Heupel et al. 2007). The habitat of these nurseries tend to be
found in shallow waters, and are assumed to have higher food abundance or lower
predation risk compared to adult habitats (Dahlgren et al. 2006).
Thanks to the advancement of
satellite tags, scientists are able to see where and when White Sharks migrate
and how long they stay in that particular area. According to Chris Lowe, a
professor at California State University, Long Beach, a White Shark nursery is
located off the coast of Santa Monica Bay, California. His research shows that
this is a hotspot for many juvenile White Sharks. These areas provide
protection from larger animals as well as an abundance of prey (Martichoux 2017).
With the help of satellite tags, a
new nursery site was discovered off the coast of Mexico: Bahia Sebastian
Vizcaino. Bahia Sebastian Vizcaino is a warm lagoon off the coast of Baja
California (Domeier and Nasby-Lucas 2013). This location is an ideal area for a
nursery because it is able to support a large population of newborns and juveniles.
Once this location was confirmed as a White Shark nursery, the Mexican
government, with the help of international researchers, implemented a complete
ban on all fishing in these nursery habitats and the mandatory release of
incidental catches. Implementing this ban has allowed for the young White Shark
populations to thrive without the threat of gillnets or longlines catching
them. Although the fishing of these
sharks is illegal, local fisherman still end up with unwanted sharks in their
gear in nearby waters. To help reduce the number of sharks that are killed
every year by improper catch-and-release methods, researchers have gone out and
educated the locals on the regulations and how to properly and safely remove
live White Sharks from their gear without killing them (Oñate-González et al. 2016).
Over the past several decades,
White Sharks in the Atlantic have been declining, but today they are on the
rise. Off the coast of Long Island, New York, a huge discovery was made. The
first ever North Atlantic White Shark nursery was located. Chris Fischer of
Ocearch says this may be the most important discovery that has ever been made
on the ocean. It is believed that young White Sharks spend the first 20 years
of their life in this area. This discovery of the Atlantic nursery allows for
the government to protect and understand more about White Shark juveniles. With
the new discovery of this nursery, scientists have been able to tag the pups in
the Long Island waters. They hope that by doing this, the pups will give them a
better understanding of how essential these waters are for their survival (Daley
2016).
The advancement of technology
allows for researchers to see real-time movement of these sharks. Ocearch is a
research organization that tags sharks and watches their movements in the
ocean. Research like this that is available to everyone allows for a larger
understanding of sharks. Ocearch allows for non-scientists to interact with
shark research and watch their favorite sharks as they move throughout the
ocean. The image below shows a snapshot of Ocearch real-time White Sharks.
Based on the sharks that have been tagged, other possible
White Shark nurseries include locations such as off the coast of Australia and
South Africa. Future research will include a focus on what exactly happens in
these nurseries. There is a lot of information on adult White Sharks, but
gaining knowledge on the young will allow for stronger management and
conservation plans for the population. Now that we know where they are located,
we need to know how they are used.
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| Nursery areas discovered for Great White Sharks along southern California and Baja California. Monterey Bay Aquarium. |
It is thought that White Sharks
spend their first 20 years in these nurseries (Daley 2016). It’s important that,
when these nurseries are discovered, governments do everything they can to
protect the area. Making shark nurseries a marine protected area (MPA) would
allow for stronger conservation and management methods. MPAs are bodies of
water that are protected by the government. These come in a variety of forms
and have multiple purposes (NOAA 2017). MPAs help conserve, manage and protect
marine waters. It is crucial to prioritize management plans such as MPAs when
we locate areas such as shark nurseries (Dahlgren et al. 2006). The majority of
shark nurseries have a no fishing ban over the region. This allows for the
newborn sharks to mature without the threat of over fishing and the impact of
humans (Oñate-González et al. 2016).
White Sharks play an important
role in the ocean ecosystem as an apex predator. Identifying shark nurseries
and documenting the specific geographic areas that are essential for the
preservation of threatened or endangered species are important steps for the
conservation and sustainable long-term management of shark populations (Oñate-González et al. 2016). Based on the known locations of the White Shark nurseries,
we can assume that they look for areas that are well protected along the coast
and that are abundant in prey. Making known shark nurseries into MPAs would
allow for the pups to mature without any threats such as gillnets, longlines,
and overfishing. Understanding all aspects about White Shark nurseries will
allow for stronger conservation efforts in the future.
References
Dahlgren, C. P.,
G. T. Kellison, A. J. Adams, B. M. Gillanders, M. S. Kendall, C. A. Layman, J.
A. Ley, I. Nagelkerken, and J. E. Serafy. 2006. Marine nurseries and effective juvenile habitats: concepts
and applications. Marine Ecology Progress
Series 312: 291-295.
Daley, J. 2016. Rare
Great White Shark Nursery Discovered Off the Coast of New York. Smithsonian.
Web. Available: https://www.smithsonianmag.com/smart-news/great-white-shark-nursery-discovered-near-new-york-180960278/
, August 2016
Heupel,
M., Carlson, J., & Simpfendorfer, C. 2007. Shark nursery areas: Concepts,
definition, characterization and assumptions. Marine Ecology
Progress Series 337: 287-297.
LaScala-Gruenewald, D. 2017. International partnership confirms a new Baja nursery area for white sharks. Conservation and Science at the Monterey Bay Aquarium. Available online at https://futureoftheocean.wordpress.com/2017/03/30/international-partnership-confirms-a-new-baja-nursery-area-for-white-sharks/ , 03/30/17.
Martichoux, A. 2017. Great white shark 'nurseries' discovered off Southern California coast. SFGATE. Web. Available: https://www.sfgate.com/local/article/Great-white-shark-nursery-discovered-off-Southern-11281529.php , July 2017
NOAA. What is a
marine protected area? National Ocean Service website, https://oceanservice.noaa.gov/facts/mpa.html,
10/10/17.
Ocearch. 2018. Global
Shark Tracker. Screenshot. Available online at http://www.ocearch.org/#Home Accessed
April 1 2018.
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