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Crystal clear, deep blue waters surround the Lakshadweep islands. The waters are so transparent you could see a green turtle chomping on seagrass a whopping fifty feet away. These tiny islands peek out above the Laccadive sea, just about four hundred kilometers off the coast of the Indian state, Kerala. The islands are made of calcium, built from twelve thousand years of coral growth. Many islands are uninhabited but for swaying coconut trees. Peaceful lagoons churn only during the monsoon rain. It’s the picture of calm above the waves, but beneath them? Coral reefs teem with life.
Dr. Rucha Karkarey has been working in these islands for over a decade, describing and understanding life under the water. “Back when I started, just a handful of people were doing underwater work,” she says. “Most of the work was in fisheries, doing boat surveys, that kind of thing.”
It was during an underwater survey that Rucha made a discovery that would change the course of her career – and the way that fish biologists viewed one particular group of fish. They were visiting a new site, having marked it out on a map earlier. A while into the survey, they witnessed a massive shoal of fish. It wasn’t a simple barracuda or tuna, famous for their huge shoals. It was an aggregation of the squaretail grouper, which Rucha calls the “leopard of the sea”.
The square tail grouper is a rare reef inhabitant. They’re piscivores, and eat other fish. Ecosystems usually have very few predators. You need a lot of prey to just sustain one. This is why every level on the food chain has fewer individuals than the one below it. On most reefs, you’d be lucky to spot one or two groupers – just like a forest can’t host more than a handful of leopards.
It’s also a bottom dwelling fish. They prowl reefs from below, swimming up to capture unsuspecting prey. They use the complex corals to hide their movement, like “a leopard using foliage”, Rucha remembers fondly, smiling.
The most striking similarity are its spots. Usually, the fish is pale brown, and dotted with black splotches. Unusually, the square tail grouper can also change colors! Sometimes, it turns entirely black. They’re also territorial, defending patches of the reef from other groupers.
Those two characters made what Rucha found even more surprising. Thousands of groupers, crammed into one reef. It was like “a thousand leopards on an area the size of a football field”.
The sight stunned Rucha and her team. Although they had heard about aggregations in documentaries and textbooks, seeing it live was an entirely different experience. It was unexpected, as grouper aggregations hadn’t been reported from India before. The island above was sparsely inhabited with a population of 200 residents, many who were posted there temporarily from other islands. The region was occasionally fished, but for tuna in the open sea, which took place far from the shore.
“We were at the right place at the right time,” Rucha recalls the day. The aggregation begins around the new moon, taking place every month from November to February. They managed to visit the reef on one of the twenty five days in the entire year when the aggregation took place. “We just dropped everything, all our data collection, everything we were supposed to do. The sight impacted me so much that I’ve devoted my entire research career to this.”
Dr. Karkarey had already begun her PhD on fish behavior when she encountered the aggregation, and had to beg her supervisor to make the sight a part of it. Even at the outset of her PhD, she knew groupers were an incredible family of fish. They live an astonishing 20+ years, which is rare for a bony fish. Their long lifespans and memories make them surprisingly resilient.
The reefs of Lakshadweep have undergone tremendous challenges, due to climate change and coral bleaching. Reef fishing has begun, adding to the pressures that the reefs face. The complex structures are breaking apart, reducing the cover that the groupers rely on to hide and feed.
“Surprisingly, they seem to be coping well,” Rucha says, describing the groupers “Many of them don’t seem to be dying younger. They respond with changing their feeding and mating behaviors, learning over time. Their long lifespans may have something to do with their ability to cope with change.”
There’s still so much to uncover about grouper aggregation. It seems the same groupers come back to the same reefs, year after year.
“There’s one fish we’ve seen two years in a row. He has a little spot across his mouth that doesn’t change when he changes colors. It looks like a mustache, and we call him Murugan.”
It’s possible each grouper can be individually identified, much like leopards, using their spots. “It’s an excellent way to incorporate AI into ecology”, Rucha proposes “If there’s someone willing to help me figure out how to automate recognition of individual groupers, I’d love that!”
As much as technology gives us a way to move forward, Rucha also highlights the importance of consolidating the knowledge that already exists.
Ways of knowing
“About ten minutes after we saw the aggregation, my field collaborator, Umni kind of got to his knees on the seabed,” Rucha narrates. “I wasn’t sure what was happening. He had his palms up and then I realized he was praying.”
Umni has worked with Rucha for many years now, and she finds him an invaluable source of knowledge. Right before the aggregation, Umni welcomed a newborn son.
I hope in thirteen years this aggregation still exists, and I can bring him here to show him.” Umni told Rucha.
Corals and fishing are part of the rich cultural tapestry of the Lakshadweep islands. Older buildings were made of coral debris that washed up on the sandy beaches. It’s an ethical quandary that Dr. Karkarey still struggles with. Fishing is central to life on the islands, but continues to affect the coral reef community. Certain kinds of fishing are more unsustainable than others, and there may be a middle ground.
Rucha believes that part of engaging in sustainable fishing practices is to involving local communities with fish in more than one way.
“Most people, the way they engage with the fish is only when it’s dead.” Rucha notes. “It’s only on the plate, and they don’t see anything other than that.”
Recently, she’s been branching out into filmmaking. It’s a way to involve local communities in the stories of fishes before the plate. Documentaries have been a vital way that Rucha herself has engaged with the marine world. She notes that films like My Octopus Teacher and the Blue Planet series were part of her journey too.
“The response has been very positive. People didn’t even know things as incredible as the aggregation took place”.
It’s definitely a change from the way people have practiced ecology so far, and not the only one Rucha has been a part of.
Fish behavior, like many other spaces in ecology, hasn’t been the most inclusive. It’s a field that many women have been excluded from, and part of it is the challenges that come with life on the boat.
“It was definitely hard.” Rucha remembers “You’re on a boat trip for eight, nine hours and we had to do things like jump into the water to pee. One of my colleagues couldn’t change her tampon for nine hours and she got a UTI. It was entirely avoidable!”
Now in a position to make change, Dr. Karkarey has been improving field practices to make them more inclusive.
“We have these little foldable changing rooms now,” she says. “You can get into and out of your wetsuit on the boat without anyone seeing. I used to feel bad to ask for accommodations, and as a student especially you’re so afraid of taking up space and inconveniencing others”
Although marine biology is a field full of challenges, it can also be immensely rewarding. Mentors like Rucha are paving the way to making a better, more inclusive field that’s still making fascinating discoveries about the underwater world.
Flesch Kincaid Grade Level: 7.7
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