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What’s next for Air Jaws? Research Priorities for The Great White Shark

Since the beginning of Discovery Channel’s Shark Week, viewers have been mesmerized by the great white shark (Carcharodon carcharias). The great white shark coverage outshines the rest with television specials like the Air Jaws series filling many of the week’s time slots. There are numerous unanswered questions about its ecology, physiology, and relationship with humans. To address the unanswered questions about great white sharks the authors polled 43 experts to determine what topics are priorities for great white shark research.

Article

Huveneers, C., Apps, K., Becceri-Garcia, E. E., Bruce, B., Butcher, P. A., Carlisle, A., … & Daly-Engel, T. (2018). Future research directions on the ‘elusive’white shark. Frontiers in Marine Science, 5, 455.

Background

Since the beginning of Discovery Channel’s Shark Week, viewers have been mesmerized by the great white shark (Carcharodon carcharias). The great white shark coverage outshines the rest with television specials like the Air Jaws series filling many of the week’s time slots. Based on the amount of time allotted to this species you would think researchers know almost everything about this hypercarnivore. However, despite all of the Shark Week specials, media attention, and films, great white sharks are very mysterious. There are numerous unanswered questions about its ecology, physiology, and relationship with humans. Great whites are inherently hard to study due to their low abundance and pelagic habitats. To address the unanswered questions about great white sharks the authors polled 43 experts to determine what topics are priorities for great white shark research.

Study Goals

Forty-three respondents were separated into four affiliated groups: government employees (33.3%), university academics (28.6%), Ph.D. students (16.7%), and post-doctoral fellows (2.4%). Looking at the respondents from additional angles there were other divisions. The majority of respondents (81.4%) were research scientists, while only 9.3% were managers. A large portion of the respondents were male (74.4%) and the majority of all experts (60.4%) had been working with white sharks for more than 10 years. The Eastern Pacific Ocean had the greatest representation (42.9%); while, the Western Atlantic had the least (4.8%). The survey responses were divided into the top 10 priorities from three groupings and sorted based on the priority each research question was given in that category.

Fig. 1 The top 10 research priorities for great white sharks and the percentage of experts that voted for each priority.

Organismal Biology:

 What is the size and status of white shark populations? – Great white shark population sizes and trends are very important for implementing management strategies. There is some evidence that overall great white sharks have low to moderate population sizes, are vulnerable to exploitation, and have undergone declines historically. While it is easy to make general statements like these, the authors note that population studies on great whites are often data limited which can lead to undefined or vague conclusions. The result is that more work is required using interdisciplinary or integrated approaches that combine multiple methods to reduce uncertainty.

What are the key parameters necessary to quantify the reproductive output of white sharks? – In the case of reproduction, researchers know that great white embryos eat unfertilized eggs in the womb and may even rely on an oil-rich “milk” produced by the mother. There are also rough estimates available for average litter size and gestations period for this species. However, our understanding of great white reproduction is poor at best. In general, great white shark reproductive biology is a pressing issue for this species and according to the authors represents a pressing research concern.

Ecology:

Ecology is an interesting aspect of white shark research. Many of the questions are intertwined and can be uniquely covered together. For white sharks the pressing ecological questions are:

  1. What Are the Mechanisms (Biotic and Abiotic) Driving the Distribution, Movements, and Migrations of White Sharks?
  2. What Are the Critical Habitats of White Sharks and How Do They Change with Ontogeny?
  3. Where and How Frequent Are White Sharks Outside Their Key Known Hotspots?
  4. How Can We Improve Our Understanding of White Shark Diet to Infer Drivers of Movements and Habitat Preferences, and Flexibility in Trophic Role?
  5. How Will Climate Change Impact White Shark Populations?

Fig. 2 Known white shark aggregations (pink) and other confirmed habitats (blue) using tracking data. Experts are shown as torsos in are of focus.

For some aggregations or areas where great white sharks gather in concentrated groups researchers have been studying the mechanisms driving these gatherings for years (if not decades). In some locations such as the Mediterranean and South America there are numerous records of white sharks but these populations are hardly studied. The environmental and ecological mechanisms that drive movements to and from these locations are still a mystery. All of these questions are also subject to change depending on the life history of the shark.

Ontogeny is the term for changes that species go through in habitat use, diet, and other life history characteristics as they age. Scientists current understanding of critical great white shark habitat and diet is the result of fisheries records and tracking research. There have been many new modeling techniques that allow research to predict ideal habitats for sharks. However, this type of suitable habitat modelling has not been done for most great white shark subpopulations. The authors also note that the majority newer modelling approaches and tracking research favors older great whites while juveniles are a mystery. In general, bridging the gap in critical habitat and behavior for great white sharks at all life stages is an immediate research direction for managing this species.

Species movements in the ocean and on land are driven by the need to reproduce, feed, and find suitable habitats. The previous six questions have focused on these issues in relation to modern populations in the current environment and have described necessary research directions for current environmental conditions. However, the environment is undergoing a rapid change and the ocean is projected to warm several degrees over the next century. The authors noted that the great white shark is relatively temperature tolerant and moves over great distances allowing for sharks to swim to warmer or cooler water as necessary. However, smaller white sharks that rely on coastal waters for nursery habitat will be more susceptible to environmental changes. With the level of uncertainty this climate change creates researchers can only predict what will happen based on modeling and similar events in the fossil record. As covered by the respondents these approaches should also cover the impacts of climate change on prey species which is likely to have a greater impact on white sharks in the future.

Socio-economics, Conservation, and Management:

How Can We Quantify and Alleviate Current Threats to Adequately Manage White Sharks and Ensure Their Conservation? – Many of the known white shark populations are covered by some form of protection. Despite country level regulations to protect white sharks, many often cross jurisdictional boundaries and travel into international waters during their travels complicating management. Many of these sharks use waters frequented by commercial fisheries at some point in their life increasing the risk of capture. In order to better understand these interactions further research on commercial bycatch mortality and post-release mortality across different life history stages is necessary.

Fig. 3 Yearly publications about white sharks for each region.

Can We Reliably Assess and Significantly Reduce Human–Shark Interactions, and Influence Public Perception of Shark Bite Risks? – Globally, shark bites and white shark bites in particular are extremely rare. However, when bites do occur there is generally a public push to enact policies to reduce human – shark interactions ranging from initiatives to educate the public on avoiding such incidents to outright culls or the targeted killing of sharks. Policies such as culling are often ineffective at reducing shark bites and harmful to the overall shark population. Additionally, several varieties of personal shark deterrents have been created to reduce bites but there has been limited testing on how effective these devices are. Long term documentation of shark attacks has provided some insight into the ideal conditions leading up to a bite allowing researchers to better provide public education on how to mitigate such events. Despite these measures, future work will be necessary to find the most efficient method of changing the publics perception of white sharks and mitigating the occurrence of shark bites.

Figure 4. The number of annual publications focusing on white sharks.

What Are the Socio-Economic Benefits and Ecological Effects of Wildlife Tourism? – To put it bluntly shark diving is a major tourism industry (US $314 MILLION) and cage diving with great white sharks contributes significantly. Following educational initiatives, white shark cage diving can further conservation mentalities by providing real-time interactions with the animals. However, how effective this industry is at maintaining or fostering conservation attitudes in participants is poorly studied. Following a conservation mentality, the authors of the article also noted that in South Africa and Australia cage diving has been shown to change white shark residency, activity, behavior, and habitat use. Cage-diving has even been claimed to result in white sharks associating humans with food and increases in shark bites as a result. Yet any evidence of causation between bites and cage diving has not been studied and represents a future direction. Similarly, the lack of aggregations that are not exposed to tourism has made it difficult to examine the impacts of cage diving on individual shark fitness. Both of these represent important priorities for future white shark research.

Final Thoughts

Covering a detailed survey of so many different experts on research directions is difficult. Each respondent likely has different research questions and priorities in mind. Some of them may not have been included in this article. However, the goal of this article was not to cover EVERYTHING white shark related. It was to establish the 10 most pressing research questions related to great whites. The star of Shark Week has so many remaining questions about its biology, ecology, and relationship to humans that my curiosity has been piqued and hopefully yours has as well.

 

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