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Top predators play a key role in maintaining the health of open ocean ecosystems. Understanding how they relate to their environment is fundamental in order to monitor their populations and the state of the marine environment. White sharks, among others, have been tracked using Argos satellite telemetry, and their path compared with ocean eddies and meanders to study where they can feed in not-so-rich areas of the ocean.

How white sharks navigate with respect to ocean features

White sharks (Carcharodon carcharias) are among the top predators of the ocean (“Jaws”, in the movie, is supposed to be a white shark – albeit a gigantic one). Such a predator is often detected in the open ocean. There, phytoplankton, considered as the base of the food chain, is rather scarce, and mostly concentrated in eddies or meanders. These structures, about 50 to 200 km wide, are also known as “mesoscale” features to physical oceanographers.

Diving patterns 

Two white sharks were fitted with surface Argos position tags, so as to have precise locations that made it possible to co-locate them with mesoscale features with sufficient accuracy. One of them also had a pop-up archival tag recording diving behavior allowing to link different diving patterns to different locations. Both sharks were located preferentially within eddies and meanders. In particular, they spent more time in the core of “anticyclonic” eddies (warmer than the surrounding ocean) than in their reverse version (colder). The double-tagged shark also showed a different diving behavior in the two kind of eddies, diving at 1000 m- 200 m (known as the “mesopelagic” or “twilight zone”) around the time of sunrise and sunset in the anticyclonic eddies more often. These patterns could be linked with the higher energetical need energy to regulate body temperature in a colder surrounding.

Protective measures

This type of knowledge can be used to better understand the behavior of animals, prioritize regions of the ocean that are particularly important for their foraging behavior, inform models and policies to design sustainable fishery policies and effective marine protected areas.

One of the sharks’ track overlaid on sea surface height anomalies from altimetry satellites (Credits Applied Physics Laboratory, University of Washington) (note that such maps can now be plotted for the last year using the “Met-Ocean” feature on Argos web)
One of the sharks’ track overlaid on sea surface height anomalies from altimetry satellites (Credits Applied Physics Laboratory, University of Washington) (note that such maps can now be plotted for the last year using the “Met-Ocean” feature on Argos web).

 

Photo: One of the tagged white shark (Credits OCEARCH)

References

  • Peter Gaube, Camrin D. Braun, Gareth L. Lawson, Dennis J. McGillicuddy Jr, Alice Della Penna, Gregory B. Skomal, Chris Fischer & Simon R. Thorrold, 2018: Mesoscale eddies influence the movements of mature female white sharks in the Gulf Stream and Sargasso Sea, https://doi.org/10.1038/s41598-018-25565-8

Links

20.03.2019 Flash news Argos buoys to help in clean-up efforts in the Atlantic Ocean after the Grande America

The CEPPOL (http://ceppol.fr/fr/), the French Navy’s Practical center of expertise for pollution control, uses Argos buoys to track pollution when an oil spill occurs at sea. This has been the case in the Atlantic Ocean since March 13, following the sinking of the Italian ship, Grande America, which emptied 2,200…

18.03.2019 Flash news Argos, satellite telemetry solution for new low-cost European WAVY drifters

The Argos system made it possible to relay the first in-situ observations of the open ocean by satellite in the early 1980s and continues to be a relevant technology for ocean science today, especially given that the new Kinéis constellation will launch 20 Argos-compatible nanosats starting in…
One of the tagged white shark (Credits OCEARCH)

25.02.2019 Animal tracking applications White sharks in eddies and meanders

Top predators play a key role in maintaining the health of open ocean ecosystems. Understanding how they relate to their environment is fundamental in order to monitor their populations and the state of the marine environment. White sharks, among others, have been tracked using Argos satellite telemetry, and their path…
whale

15.02.2019 Animal tracking applications Argos celebrates World Whale Day

Whales are some of the most fascinating creatures on Earth. They inhabit all of the world’s major oceans, including the Arctic, the Antarctic and the tropical waters of the Atlantic, Pacific and Indian oceans. From the blue whale, which is the world’s largest, to the elegant narwhal, these enigmatic marine mammals attest…
narwhal

15.02.2019 Animal tracking applications Understanding the impact of human activity on narwhals in the Arctic

Wide-scale changes are taking place in the Arctic, with warmer temperatures leading to shrinking summer ice coverage.  More ice-free water means easier access for vessels and industrial operations, such as exploration for oil and gas, shipping, sand dredging and fisheries. Faced with these changes, how can we protect vulnerable Arctic marine…
Magellanic penguins, including one with an Argos tag on its back, and one Humboldt penguin (credits Antarctic Research Trust)

15.02.2019 marine animals Shedding new light on South American penguins home range

Humboldt and Magellanic penguins live in the southern tip of South America. On the Pacific coast, they benefit from the high productivity of the Humboldt Current but are also threatened by artisanal fisheries. They are thus considered as either vulnerable or near threatened, and conservation measures should be taken. Their…
A drifting CO2 measuring buoy just before deployment (Credits JAMSTEC)

31.01.2019 Oceanography and meteorological applications Measuring CO2 in faraway regions of the ocean

The ocean is one of the most important carbon sinks on Earth. Thus, accurate estimation of CO2 uptake by the ocean is important for predicting global climate change. Automated buoys with data collected by Argos satellite telemetry make it possible to measure CO2 over the whole ocean during long periods,…

24.01.2019 Flash news Argos system contributes to Argo program milestone

Last month, the international Argo program reached a very important milestone: Over 2 million ocean profiles have been collected by Argo since 1999, greatly improving the understanding of the world’s oceans. The Argos satellite telemetry system has contributed to this success, by relaying 70% (1.5 million) of these precious ocean…
An eel in the sea with a pop-up tag. Credits G. Simon, Perpignan University

17.01.2019 Animal tracking applications Eels, long-range travellers

Eels, threatened by pollution, virus and parasites, overfishing, habitat loss and climate change have seen their population drop in the past decades. Their life and behaviour are studied to better understand the causes of this decrease. Their migration – when adults cross the Atlantic to the Sargasso Sea to reproduce…

08.01.2019 Animal tracking applications Argos system contributes to French National Action Plan to protect Marine turtles in the Caribbean

In the French West Indies, five turtle species are threatened. This includes the hawksbill turtle, green turtle, leatherback turtle, loggerhead turtle and olive Ridley turtle. Three of these species are tracked closely by national and local authorities. Protecting wildlife with Argos The Argos system is one of the prinicipal technologies…