Close Encounters with Sharks | Zoya Tyabji
The decline of shark populations due to human intervention is a cause for great concern. In this week’s post Zoya Tyabji (Inlaks Ravi Sankaran Programme, 2018) highlights their significance in aquatic ecosystems and threats they face today.
1. What inspired you to study sharks?
I have held a fascination for the marine realm for as long as I remember. However, studying sharks was something I stumbled upon. I was working on a project to study coral reef resilience in the Andaman Islands. Our work was based in the Marine National Park where we dived to collect data. During this time, I was surprised that we did not encounter a single shark. We read about the important and integral part that sharks play in ecosystems, especially in coral reef ecosystems, and it just perplexed me that text book theories didn’t match practical empirical knowledge, and that these animals were not included while studying the resilience of an entire ecosystem!
This made me contemplate about the fate of sharks and their ecological role in ecosystems. I interacted with many locals and fisher communities of the islands, who remarked on their steep population declines in the last few years due to overfishing, and a visit to the fish-landing site confirmed the same and introduced me to the complexities of conserving them. The fate of an animal that was so misunderstood due to its negative image caused by movies like Jaws; mysterious, since we don’t even know what species exist in our waters; and their vulnerability in the face of overfishing and anthropogenic disturbances, inspired me to study them.
2. How do sharks contribute to the ecosystem? Or what makes sharks so integral to the ecosystem?
Scientific studies have indicated that many large shark species act as ‘apex predators’, they have few natural predators and thus help regulating and maintaining the balance of the food web. Apex predators not only affect population dynamics by consuming prey, but they also control the spatial distribution of prey through intimidation which can cause species to alter their habitat and activity level. For example, a study (Heithaus et al. 2014) showed that the presence of tiger sharks influenced the activity level of green turtles, in turn affecting the grazing of seagrass. Thus, it causes a top-down control in lower trophic levels. Further, since sharks have a varied diet, they may prevent one species from monopolising a limited resource, thus indirectly leading to an increase in diversity of species.
However, sharks are diverse animals, with more than 500 species recorded. Further, variable life history characteristics are seen between species and regional differences within species. Many shark species are also meso-predators, that is, they are preyed upon, especially during their juvenile stages, and are predate during their adult stages. In most parts of India, we still lack basic information, such as the species present in our waters, and thus, how they contribute to the local ecosystems. Further, with the alarming rate our oceans and seas are changing, and overfishing in the nature of these changes, we need to readdress the role of these species in our ecosystem. However, the overfishing of these species can cause cascading effects that can result in economically and ecologically devastating consequences which we might be unaware of.
3. What are the main dangers to sharks today and what are the preventive methods you employ to ensure they do not go extinct?
Overfishing is one of the most global threats to sharks today, along with habitat-degradation, resource exploitation, etc. In India, sharks are often caught as by-catch with a few targeted shark fishing ongoing. While there exist seasonal bans and ten species of sharks and rays listed under the Indian Wildlife (Protection) Act, 1972, the fact that we still lack basic information, such as the species found in our waters, their life history characteristics, their stock catches, etc., which severely hampers their effective conservation.
A few preventive measures would be to generate baseline information and monitor stock populations and population trends. Also, to direct conservation efforts on a holistic approach based on the baseline information, in particular on the ecology of sharks, socio-economics of fishers and fishing pressures (including gear selectivity, stock structures, etc.). Lastly, to ensure that policies are science-based, to work with and not against stakeholders, especially the fisher community, and to implement the National Plan of Action for sharks.
4. Have you ever had a close encounter with a shark?
While scuba-diving in Indonesia in 2017, I was suspended in the blue, awestruck by the psychedelic colours that the reef threw at us – I was imagining how my friends and colleagues would conduct fish transects here, as the diversity and abundance was baffling. And then, by chance, I happened to look down into the unending depths – and saw something cut through the water gracefully with its white flank and black tips. It was a blacktip reef shark and my first live shark ever!
After sampling over a thousand dead sharks harvested by fishermen at fish-landing sites (which is what my work entails), I had seen my first live shark underwater! The shark was a contrast to the reef in its simplicity of colours and conveyed power and grace as only an apex predator and a keystone species. The moment was a fleeting one, but powerful enough to motivate me to get back to sampling dead sharks in the Andamans in the hope that I can make a difference and enjoy sightings like this one in future during the course of my work there.
Thanks to the Ravi Sankaran Inlaks grant I got my second opportunity to interact with live sharks in 2019 where I had several encounters with them. The mixing of a cold current and warm current in South Africa, render their marine diversity to be high and unique. Sixty percent of the sharks in South Africa are endemic with some unbelievably fascinating sharks, from a bioluminescent shyshark that glows under black light, to the sixgill cowshark which is one of the most ancient species, to the great white shark, an apex predator. During the internship, we were taught how to handle sharks, thereby ensuring the safety of both parties. We also learnt various methods to catch them, along with various tools and techniques to answer pertinent ecological questions about them.
I am hopeful that I can apply what I learnt in India and have close and safe encounters with them in India’s waters though.
5. Is there anything that you have learnt during your research that has surprised you or made you rethink your understanding of marine life?
I started studying sharks with sheer curiosity and a perception that it was an animal that needed saving through top down approach of strict protection and management measures. However as I spent more time studying sharks at the fish-landing site, my interactions with fishers changed my perception and convinced me that it was a holistic approach of mix of top-down and bottom-up that we needed to take, one that certainly involves the animal, but we also need to turn around and listen to local communities that depend on the fisheries for their livelihood. It is a multi pronged approach of understanding species-specific life history characteristics of sharks, socio-economics and fishing gear selectivity to achieve conservation.
