Hakai Magazine

The skull and brain of one of the four salvaged blacktip sharks, post-dissection. Photo by David Shiffman
The skull and brain of one of the four salvaged blacktip sharks, post-dissection. Photo by David Shiffman

The Scientific Afterlife of Sharks

When four sharks died in Florida, their corpses were split among a dozen research projects.

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by David Shiffman

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A few months ago, a local SCUBA diver called our lab to tell us that he’d found some fishing gear abandoned on the seafloor. It wasn’t the fishing gear he thought we’d want, but what was attached. Stuck in the longline’s hooks were four adult blacktip sharks, their bodies lifeless.

Throngs of animals are currently rotting at the bottom of the sea as the victims of “ghost fishing”—caught by derelict traps and nets that continue to fish long after they’re abandoned. But the SCUBA diver wanted to know if we would take these sharks in and give them a second life as subjects for scientific research.

The shark conservation lab where I work at the University of Miami had no need for the blacktips, as our research is entirely based on catch-and-release, non-lethal methods. But we agreed to put out a call to other labs. What we got was a feeding frenzy as hungry researchers from all over the world jumped at the chance to get valuable samples.

Overnight, we heard from 13 researchers who wanted pieces of the sharks. A comparative neurologist wanted their brains. Another scientist took their vertebrae so that she could count the rings—as one might with the cross-section of a tree—to determine the sharks’ ages. A toxicologist took the livers to measure pollution exposure, and the hearts and gills will be used in a comparative study of shark circulatory systems. The reproductive tracts will help researchers understand how long it takes sharks to reach maturity and the number of offspring they have each year. This will, in turn, help determine how quickly populations can recover from overfishing. All told, these four dead sharks will benefit a dozen research projects in the United States, the United Kingdom, Canada, and Australia.

Scientists estimate that more than a quarter million sharks are killed every day by commercial fishing, and essentially none of them are used for research. What’s more, shark researchers have no organized system for coordinating the gathering and sharing of samples. We had to find the recipients for our blacktips through Facebook, Twitter, and email listservs.

In the future, more coordination among researchers, and between fishermen and the scientific community, could lead to fewer sharks dying for research, more data from sharks that are already being killed, and improved conservation for some of the most threatened and misunderstood animals on Earth. But in the meantime, the reality of scientific research poses a dilemma for a conservation-minded researcher.

I like to call the global shark crisis “the worst environmental problem you’ve never heard of.” One in four shark and ray species are considered threatened with extinction by the IUCN Red List, and scientists have observed population declines of 90 percent or more in several species.

To protect these animals we need to understand their biology, their behavior, and their life history. And to do that, we need to study sharks—real sharks. Many scientific studies require tissue samples or measurements, some of which are impossible to gather from a living shark. So, sometimes, protecting sharks means having to kill sharks.

While opportunistic sample gathering—as with our four salvaged blacktip sharks—can help reduce the number of sharks killed, too strong an aversion to taking sharks can also leave research projects without enough samples.

The number of sharks sacrificed for research “is kept to a minimum for ethical reasons,” says marine biologist James Sulikowski. “However, low sample sizes are not ideal, and they usually provide more questions than answers. In addition, making assumptions without proper data can lead to disastrous outcomes.”

Changing attitudes and new scientific methods including satellite telemetry and non-lethal diet analysis mean that fewer sharks are now being sacrificed for science says Christopher Lowe, the President of the American Elasmobranch Society.

“Dwindling shark populations have certainly driven more scientists to consider whether lethal sampling is needed to answer certain questions and to search for alternative approaches,” says Lowe. “While it’s good that we’ve developed new methods and technology to answer more questions that requires killing fewer sharks, there are some questions that unfortunately require killing some sharks to gather certain data that are absolutely essential for improved management and conservation.”