The sun was just breaking over the calm coastal waters as Dr. Diego Cardeñosa’s team loaded their nets and tagging gear onto the boat. Days spent tracking scalloped bonnethead sharks (Sphyrna corona) usually meant long hours of patient searching, but recently something unexpected kept surfacing in their data. Alongside the familiar hammerheads, the team began spotting more Pacific smalltail sharks (Carcharhinus cerdale) than ever before. Quiet and elusive, these lesser-known predators seemed to be appearing in the same shallow bays and estuaries, hinting at a possible connection between the fates of two very different species.
“Coastal ecosystems such as mangroves, estuaries, and shallow bays are vital nurseries for countless species. Small hammerheads, including bonnetheads, scalloped bonnetheads, and scoopheads, as well as smalltail sharks and even species we’re only beginning to understand all rely on these habitats during critical stages of their life cycle,” said Cardeñosa over e-mail about what was unfolding in the Cachuda Project. “When these ecosystems are lost, it isn’t just a single species that vanishes; entire communities of marine life collapse together.”
The Pacific smalltail shark is a lesser-known member of the requiem shark family (Carcharhinidae). For nearly 60 years, it was thought to be the smalltail shark (Carcharhinus porosus), but in 2011 it was recognized as a distinct species. It inhabits the eastern Pacific from the Gulf of California to Peru and is an opportunistic predator, feeding on rays, small fish, and invertebrates. Adults have even been observed preying on the young of other shark species, including hammerheads! Conservation-wise, the Pacific smalltail shark is listed as Critically Endangered by the International Union for Conservation of Nature, with populations declining due to overfishing — particularly from gillnet and longline fisheries — and habitat degradation. Despite its ecological importance, the species has not been formally evaluated under the U.S. Endangered Species Act.
The overlap between these two species’ habitats highlights a critical opportunity: protecting the scalloped bonnethead could have ripple effects, providing indirect conservation benefits to the Pacific smalltail and other small coastal sharks that share these vulnerable ecosystems. A kind of unintentional gift to other species sharing the same home. This is what scientists call “collateral conservation,” and as Cardeñosa explains, it means “that when we protect one species, especially a ‘flagship’ animal, other species nearby also benefit. It’s like buying one ticket but getting multiple entries, the effort you invest in saving small hammerheads also helps other small, lesser-known sharks and rays that don’t usually get the spotlight.” In this case, protecting nursery grounds, feeding areas, and coastal habitats for hammerheads may also provide a lifeline for smalltail sharks, bonnetheads, and even other species we’re only beginning to get to know better.
The Pacific smalltail shark doesn’t get the headlines hammerheads do. It lacks the dramatic look, the iconic fins, the media appeal that draws cameras and conservation campaigns. Yet its story is just as urgent. Its decline has been steep, driven largely by coastal gillnet and small-scale fisheries that sweep through shallow bays and estuaries where these sharks live. Unlike hammerheads, smalltails are seldom targeted for attention, and their populations can slip toward collapse quietly, almost unnoticed. In some areas, Cardeñosa notes, they have almost vanished, leaving gaps in the ecosystem that few people even realize are missing. Their scarcity underscores a harsh reality: many species fade into obscurity long before they reach the public’s radar, even when their ecological role is crucial.
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“When we protect a species like the scalloped bonnethead, we’re not just helping that one shark, we’re safeguarding the entire ecosystem it depends on. Hammerheads often share nursery grounds, feeding areas with many other species. If we protect those spaces, the benefits spill over to other small coastal species that rely on the same habitats,” Cardeñosa says. Of course, focusing on a flagship species comes with a risk. Resources and attention can become concentrated on the “star” species, potentially leaving others behind. But with intentional planning, that doesn’t have to happen. “Flagship species are powerful tools for mobilizing resources and public support, but it’s our job as scientists and conservationists to ensure those benefits extend to lesser-known species as well. That’s why we design projects around protecting entire habitats or key locations where conservation gains ripple out broadly, rather than focusing narrowly on a single species.”
Coordinated international cooperation has been crucial in protecting hammerheads because they migrate across national boundaries and rely on multiple countries to protect their populations effectively. Science-based management — from tagging programs to population modeling — has provided the evidence needed to implement fishing regulations and establish marine protected areas. Protecting critical habitats, especially nurseries where juveniles grow and learn to hunt, has been another key factor in their recovery. These lessons are just as relevant for smaller, lesser-known shark species as they too need protected areas where they can safely reproduce and grow, robust fisheries management to prevent overexploitation, and careful monitoring to understand population trends and threats. The difference? Smaller sharks rarely capture public attention or funding, making it easier for them to be overlooked. The real challenge lies in ensuring that conservation strategies are designed to benefit entire habitats and communities, not just the famous species. By integrating these smaller sharks into the broader framework of habitat protection and sustainable management, Cardeñosa believes they can create ripple effects that safeguard multiple species at once.
Genetic diversity adds another dimension to the story. “Genetic diversity is like a species’ insurance policy,” Cardeñosa explains. “It gives populations the ability to adapt to change, whether that’s fishing pressure, disease, or climate change. Without genetic diversity, even if numbers recover temporarily, a species can remain fragile and collapse again.” In practical terms, this means that two populations of the same species can respond very differently to the same threat depending on the range of genes they carry. A genetically diverse population has more options for survival, from resisting new diseases to tolerating warmer or more acidic waters. Thankfully, advances in genetic testing (like techniques such as DNA sequencing and population genomics) have allowed scientists to track gene flow between populations, identify isolated or at-risk groups, and even uncover previously unrecognized species — as has been the case for a number of sharks that were once thought to be something that closely resembled them. This data informs conservation decisions in a way sheer numbers cannot; for example, protecting a habitat that hosts multiple genetically distinct populations ensures we are safeguarding the evolutionary potential of the species, not just the individuals currently present. In a rapidly changing ocean, genetic insights are no longer optional but essential for building resilient shark populations that can withstand the pressures of fishing, habitat loss, and climate change over generations. That’s why it’s so important to bring these technologies to research teams and conservation programs around the world: making genetic testing accessible globally ensures that populations in remote or under-resourced regions can be monitored and managed effectively, giving even the most overlooked or isolated species a fighting chance to survive.
Out on the water, the scientists prepare their tagging gear, knowing that every fin they tag tells a story about the hidden connections between these two (and possibly more!) species. By continuing to track both predators, they hope to uncover just how intertwined their lives really are — which nursery areas they share, how their movements overlap, and where conservation efforts could benefit multiple species at once. But while the data is still unfolding, there are steps everyone can take right now. Supporting local conservation groups, choosing sustainable seafood, and sharing stories about lesser-known sharks helps protect these species today, even before the scientists fully understand the complex web that connects them. Every post, every conversation, and every community effort contributes to a broader network of protection, giving hidden species a chance to thrive.
The team’s encounters with Pacific smalltail sharks at the Cachuda Project are a small but encouraging sign. It’s proof that thoughtful conservation can create ripple effects through coastal ecosystems, giving multiple animals a fighting chance to survive in an ever-changing ocean. By focusing on habitats, not just individual animals, we shift our perspective from isolated species to entire ecosystems. When we conserve habitats, we’re not simply saving a single animal, we’re preserving the complex interactions and ecological processes that sustain life across the ecosystem. In many ways, this is a reminder that in nature, saving one often means saving many.
