Hammerhead shark caught for a population survey. Photo: Claudia Friess / Ocean Conservancy

While most people out on the water are trying to avoid sharks, I’m on a boat that’s looking for them. We’re trying to find out which shark species are doing well and which ones are in trouble.

The answer: it’s complicated. But one important piece of evidence is the information collected on scientific surveys of population abundance, like the one I’m on right now.

It’s my third year as a volunteer on the science crew with the National Oceanic and Atmospheric Administration. I am currently on the NOAA ship OREGON II, a 170-foot research vessel with its home port in Pascagoula, Miss.

This is the first leg of the annual shark and red snapper bottom longline survey. The survey is conducted in the U.S. Gulf of Mexico from South Texas to the Florida Keys and along the East Coast up to Cape Hatteras, N.C. That’s a total of four legs lasting two weeks each.

Our job is to go from station to station deploying a mile-long line (the longline) with 100 baited circle hooks on it, then haul back the line after an hour of soak time and process everything that is caught. We fish in depths between 60 and 240 feet.

But boat time is not cheap, so we fish around the clock to make the most of these valuable days at sea. My crew fishes from midnight to noon, and the day crew fishes from noon to midnight.

When we catch a small shark, we bring it on board, and when we catch a big shark, we use a crane-operated cradle to lift the shark out of the water and line it up alongside the boat. Regardless of the size of the shark, the most important thing is to control the head. If you do that, you won’t get bitten.

We measure and weigh each shark as well as record species and sex. Most species also have genetic samples taken and get tagged. Then we throw them back overboard. Sometimes we also catch non-shark fish, most often the highly sought-after red snapper.

By far the most common shark we catch is the Atlantic sharpnose shark, a small species that only reaches about 43 inches in total length. Other species we see are blacktips, blacknose and sandbar sharks.

Often, the bigger sharks get caught because they have eaten a smaller shark (usually a sharpnose) that had previously been caught on the hook! And then there is the occasional treat: a hammerhead or a tiger shark. Unfortunately, these beautiful fishes have become quite rare.

Aside from collecting biological data on the species we catch, the most valuable part of surveys like these is that it’s designed to track the status of these shark populations over time. Each year, the gear is fished the exact same way, and stations are surveyed randomly, which allows researchers to calculate an annual catch rate for each species.

Over time, if the catch rate increases, that indicates the population is going up. Conversely, if the catch rate decreases, that is evidence that the population is declining.

This research is important to helping increase the knowledge for these vital ocean species. The more we know, the more we can help protect them. So these surveys are much more than a regular fishing trip; they’re generating valuable data for the conservation and management of top ocean predators that are so vital to healthy, functional ocean ecosystems.

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