Marine Science & public safety in coastal areas: White Sharks and S. California.
When we talk about sharks, we always think about the different shark attacks on surfers around the world, and movies that have shown this animal as a great danger. But, what can we do to understand the behavior of this species and avoid these attacks? How can marine science help us in improving our shark-human relationship? Last month, I attended a webinar called "Shark Science and Safety" where scientists talk about their research on White Sharks in South California, and how this data can be shared with the community for public safety regarding sharks encounters. I found this information very useful and important, and that is why I want to share it with all of you. But, first, let's talk about our biggest star: the White Shark.
The White Skark (Carcharodon carcharias) is a shark species reaching at least 6 mts length in its adult phase. It has gray-brownish skin color on the dorsal part of its body, more clear by its sides, and white on its belly (ventral side). It also has black eyes and its first dorsal fin has a triangular shape. In front of its pectoral fins, and in the back of its head, we can see its gill slits. These openings allow gills to exchange oxygen and carbon dioxide between the shark’s blood and the water.
White Shark (Carcharodon carcharias). Picture: Cram Foundation
The White Shark is a wide-ranging species, especially in temperate waters of North West Atlantic, Mediterranean Sea, southern Africa, southern Australia, New Zealand and North East Pacific. Regarding its social behavior, the White Sharks are usually solitary, but they can be reunited in groups of ten or more individuals near a feeding ground. As this specie prefers continental waters, it is possible to find them in shore lines, off rocky shores and into enclosed bays, harbors or estuaries.
Regarding its reproduction, they are cannibal oophagus live-bearing sharks. This means that while the embryos is inside is mother’s uterus, it starts eating non fertilized eggs. Gestation period length is not well known, but scientists agree that it must be between 1 or 2 years. The new borns length is between 1 or 1,6 mts and females reach its sexual maturity between 12 and 16 years old, whereas males reach is at 10 years old. While they are newborns and juveniles they live by the coast in what is call nursery areas. As you can see, the White Shark has a low growth rate, which makes it vulnerable to fishing as its population do not recover fast if its depleted.
White Sharks play an important role in the ecosystem. This animal is a top predator, thus controls the population of its preys. It has a broad prey spectrum, from vertebrates to invertebrates such as cephalopods, mussels, crustaceans. Regarding its vertebrate prey, it relies on rays, seals, birds, reptiles and fishes.
Picture: Cram Foundation
Southern California White Shark population has decreased since the mid 1950s due to many reasons. One of them was because the shark fishing industry, as well as seal hunting, White Shark’s main prey. However, on 1994, California Council protected White Shark population, as a consequence, the population of White Sharks at South California start to grow. For the last 10 years, there are 5 times more White Sharks than there were before.
At the same time, Southern California is one of the most populated areas, with around 20 million people. Indeed, more people are relying on coastal areas and beaches for recreation and water sports. Even though encounters with White Sharks have been increasing because both species (humans and sharks) share the same area, there is no evidence that shark attacks have been increasing significantly. Every year, only two to five sharks have attacked a human. As both species share the same area, it is crucial to know why sharks are near the shore lines, how is their behavior and how marine science data can guide us to share our ocean in a safety way.
Last month, the Shark Lab of the California State University, Long Beach (CSULB) hosted a webinar call “Shark Science and Shark Safety Webinar” in which they share how shark science can be shared with life guards and the community in order to make better informed decisions regarding its safety at the coastal zone. The webinar is posted on YouTube, and here we would like to point out some of the info they share with all of us!
Dr. Chris Lowe is Shark Lab’s director at the CSULB, their mission is to “study physiological and behavioral ecology of marine animals, emphasizing the effect of human activity on the ocean, to utilize and develop innovative technology to answer challenging questions important for the conservation and restoration of depleted populations”.
Thanks to their research, Southern California coast can be described as a nursery ground for White Sharks. Between April and October, we can find White Sharks’ new born and juveniles at nursery grounds in Santa Barbara, Santa Monica, Long Beach/Huntington Beach & Dana Pt/St Onofre. The scientists believe these areas are nursery grounds because the coastal zone is safer to juveniles as there are less predators, it has a great availability of food, such as Sting Rays and also the temperature of coastal waters is warmer than off shore. What is more, through their research, they have realized that this nursery ground changes over time. For example, if one year, Santa Barbara was the nursery ground that gather most of the white shark juveniles, the following year, another area will be the one that gather the most.
Also, White Shark juveniles had a migration pattern guided by the sea surface temperature. As the surface temperature gets colder, they travel to the south, looking for warmer waters. They can even reach to New Mexico. When spring starts to come, they return into the Southern California area.
A PhD student in the Shark Lab studied how far from the shore line sharks are. He found that, White Shark’s juvenile can be found at around 90 m from the wave break point. Sometimes surfers can be outside the wave break point waiting for waves, so there is a greater chance to share the area with sharks, and as a result a greater chance that humans may be encounter White Sharks.
Studying how sharks behave are really important to read its body language and know how to act when we encounter one. Dr. Lowe recommends that when we encounter a shark “you should always track it, keep your eyes on it, turn your surfboard for it. A predator [like sharks] that relies on stealth, knows the gig is up if it knows it’s being watched.” Even if you do not have your face in the water, the movement of the board through its direction makes the shark think it is being observed and that means it might get bored and stop chasing you. And also, if you lost sight of the Shark, always look behind you. When a Shark moves away after an encounter, they loop around and will become behind you. So, look at your back.
What is more, when sharks are experiencing an active swim, moving fast, around in circles, going back and forward, that’s a behavior you may consider and move back to the beach. It doesn’t mean the shark is going to attack you, but it’s a behavior they have when they are looking for food, maybe some prey is near you, so it’s good to back off and don’t be in danger.
The Lab Shark at the moment is developing different initiatives in which they use data to informed life guards about Shark presence on the beach and how the community can look to their safety and shark’s one. This are some of the initiatives:
1. They have developed new technology that while it is collecting data for scientific research, it can also share real time data with life guards. They are developing a buoy that will detect the signal of a shark they’ve tagged and will send a text alert to the safe-guard about its presence. Right now, they are trying this technique with four buoys out along the coast of Santa Barbara and one in Long Beach. This information gives lifeguards data about Sharks movement, so they can make informed and safety decision.
Shark Lab's buoy. Picture: Shark Lab Instagram.
2. Another tool is environmental DNA on water samples. Lafferty et al 2018, have discovered the ability to detect sharks DNA from a water sample. They are now trying to collaborate with Laferty et al, in order to answer how long will the DNA last, how far away can we detect DNA, can they estimate the number of sharks and if it really means that a Shark has been at the area when the sample was taken. And if it works, there is a plan to integrate this technique into real-time sampling and recognition of White Shark presence along beaches at life guards headquarters.
3. The Shark Lab have designed a flyer in English and Spanish in which they informed about sharks behavior, identification and which actions may be taken for the safety of both species. This is the flyer we all must read and be ocean smart!!
Picture: CSULB Shark Lab
If you are interest in learning more about Shark Lab research, you can visit its website here, or follow its Instagram here. Also, if you are interested in watching the webinar in Youtube, here is the link.
Compagno, L.J.V., Marks, M.A and Fergusson, I.K (1997) Threatened fishes of the world: Carcharodon carcharias (Linnaeus, 1758) (Lamnidae). Environmental Biology of Fishes 50: 61-62.
Lafferty, K.D., Benesh, K.C., Mahon, A.R., Jerde, C.L and Lowe, C.G (2018) Detecting Southern California’s White Sharks With Environmental DNA. Front. Mar. Sci. 5:355. doi10.3389/fmars.2018.00355