The Powerful Effects of Baby Sharks in the Ocean

Not all sharks live up to the reputation of the great white in Jaws. In fact, very few do. But in the ocean, even baby lemon sharks instill brief but powerful moments of fear in smaller fish. 

That fearsome presence lies at the core of research by Betsy Stoner, Wilder Teaching Professor and associate professor of Natural and Applied Sciences at Bentley. Here, she shares how these moments influence ocean food chains and fish development — and why it matters to people and businesses. 

Why is it important to understand the role that sharks play within marine food chains? 

This project is about the ecology of fear. In other words, we know that predators like sharks control prey populations by directly eating them — which influences marine food webs — but we are increasingly learning that sharks also scare prey just from their presence.  

This fearsome presence influences which prey stick around in an area. Even if a shark is swimming by and not eating prey, the prey will detect the shark's presence and swim away. This has incredibly important effects on marine food webs (who eats whom), with cascading effects on marine ecosystem health. 

Why did you choose to specifically study the interaction between baby sharks and reef fish? 

We often hear about adult sharks and the role that they play in creating a landscape of fear for prey, but we don’t know if baby sharks have the same kind of effect. In other words, are baby sharks also scary to fishes like adult sharks are? To our knowledge, this really hadn’t been explored before.  

All of this came about because I was studying jellyfish in shallow-water hard-bottom ecosystems in The Bahamas, and realized that when baby sharks swam through, all the critters scattered. It got my collaborators and I thinking about whether baby sharks are fearsome in the same way the grownups are. 

What are your main findings, and why do the insights matter?  

The main research findings show that, yes, baby sharks do scare reef fishes, but only for a moment. Reef fishes recover and swim back through as soon as a shark swims away. Our research indicates that there is not much of a lasting effect from fishes being scared by baby sharks.  

Why does this matter? Reef fishes and baby sharks both live and use tidal creeks as nursery habitats (where baby fishes grow) — habitats that are critical for fish development but often are destroyed by human activities, like cutting down mangroves for development. 

Our study highlights that baby sharks and reef fishes need these habitats to survive. Baby sharks can help regulate reef fish populations just by their presence — ensuring that these nursery habitats stay healthy and functional for years to come. 

Did anything about the research surprise you? 

I was surprised that so many reef fishes don’t seem to mind the presence of baby sharks — at least after the initial ‘surprise’ of seeing a baby shark swim by.  

We did compare how reef fishes would respond to a predator (like our sharks) to a non-threatening animal of similar size (a green turtle that is an herbivore) to ensure that any difference we saw was related to the fact that a predator — and not just a large animal — had the effect on fish behavior.  

It turns out that reef fishes did flee more from the shark than the turtle. However, overall, reef fishes didn’t care much about baby sharks being around. We aren’t really sure why this is, though we have some hypotheses that we will study in the future. 

Do sharks get a bad rap? 

They sure do. When we think of sharks, many of us think of the giant and terrifying shark from the Jaws movie or have a fear of being attacked by a shark if we swim in the ocean. The reality is that sharks are generally timid and don’t want to be around people. In fact, we are statistically more likely to get crushed from a falling vending machine than a shark attack, but these vending machine “attacks” don’t make the news! 

The other reality is that sharks are being massively overharvested. Over 100 million sharks a year are killed for their meat, fins or oil with many killed unintentionally from fisheries. Sharks are the guardians of our oceans, and we need them to keep ecosystems healthy. Without sharks, we are dealing with ecosystems that are less resilient to global change. 

Thinking about this behavior as an analogy for workplace culture, do you think workplace culture can mirror a marine ecosystem — like the role sharks play in shaping everything around them?  

This is a fun question! Though I would defer to my Management and Organizational Behavior colleagues on this one, I would say that in a marine ecosystem, sharks are in some ways like really effective managers. Just as a top predator doesn’t need to constantly hunt in order to influence an ecosystem, an effective leader doesn’t need to micromanage or overly influence employees to foster a positive workplace culture.  

The presence alone of an effective manager can be felt in the healthy environment that they have worked to create — one where employees want to engage, collaborate and take risks.

What originally inspired your interest in marine life? 

My deep love for the oceans and marine life began when I was 4 or 5 years old.  

Despite growing up in landlocked Syracuse, NY, every year we went on family trips to Florida, where I would always play with marine critters that I found. On one trip, we were doing a family beach cleanup and our feet were covered with sticky oil from an oil spill. I remember thinking that we had an imperative to protect the critters that I loved from these human-driven dangers, but also to protect ourselves and ensure the future vitality of our ocean resources.  

What stuck with me is that I learned about how incredibly dependent we all are on our oceans: Every other breath we breathe is thanks to the ocean. It impacts virtually every aspect of our lives, whether we live near the coast or not.  

As an aside, my dad was a hydrogeologist who owned a company in Syracuse that would buy and clean polluted land to sell for redevelopment. So, I also grew up thinking about all the ways that business can be a huge force for good in affecting environmental change. I’ve sought to devote much of my work to finding out how we can create positive connections between various stakeholders, including business, and the oceans that allow all of us to live.

See how Betsy Stoner uses virtual reality experiences to immerse Bentley students into different marine ecosystems.

Experts are predicting a “sharky summer” with early sightings of baby great whites. What should swimmers know — and what does this trend say about the state of the ocean? 

In New England, while it may seem like white shark populations have increased, this is a reflection of the fact that they are following food — mainly seals, whose populations have seemingly increased since the Marine Mammal Protection Act took effect in the 1970s — and dealing with warming waters from ocean warming that white sharks are trying to avoid. So, an apparent increase in white sharks or a “sharky summer” really reflects their increased movements in the area.  

Related to our exposure to sharks, the general advice I tell folks is to avoid swimming during what I call “shark thirty,” which is dawn or dusk. This is when shark hunting is more likely to occur. I would also avoid getting into the water when conditions are turbid, such as murky water following rainstorms. 

In New England, an even more helpful practice would be to avoid beaches where seals are usually present, as this is the food that white sharks are after. I also have invested in a good pair of polarized sunglasses to better see what is happening in the water! 

Sharks are always in the water — even if you can’t see them. That said, the statistical likelihood of being bitten by a shark is low; you are more likely to be electrocuted by a toaster oven. But it is always helpful to practice water awareness and be on the lookout for sharks.