What 50 Years of Shark Surveys Have Revealed
Courtesy VASMAP, Batten School and VIMSA great hammerhead shark being pulled up via gurny onto the deck for a workup.
As a shark conservation scientist, one of the most common questions people ask me is, “How are shark populations doing?” To answer this question, it’s important to understand two types of fishery surveys: fishery-independent and fishery-dependent. Fishery-dependent population surveys gather data from fishermen’s catches. These data are valuable because there are many more fishermen on the water than marine biologists. However, they are limited because fishermen fish with the intent to catch as much as possible, which means they regularly change their methods to achieve higher yields. This makes sense economically but limits the scientific value of the data.
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In contrast, fishery-independent surveys are designed to use the same methods, which are scientifically more rigorous. “They provide an unbiased characterization of many different things, particularly changes in the abundance of fish populations over time,” Dr. Robert Latour, a professor at the Virginia Institute of Marine Science (VIMS) at William and Mary. “Since the survey is performed the same way during every research cruise, any changes in what you catch are due to something going on with the population, not changes in how we’re fishing.”
Kristen SharpeA juvenile sandbar shark collected in a coastal inlet along Virginia’s Eastern Shore.
History of VIMS Shark Research Program
Dr. Latour runs the shark longline survey at VIMS. Founded in 1973, two years before “Jaws” was released, the VIMS shark survey is the longest-running fisheries-independent shark population study in the world. The program was founded by Dr. Jack Musick, a legend in the field of shark science, who passed away in 2021.
During that time, the program has graduated 50 Ph.D. students who now work all over the world and has produced numerous research papers and reports on shark biology and conservation.
Courtesy Voight "Bubba" HoggeScientists on deck anxiously await the opportunity to interact with the largest shark caught and successfully worked up on the VIMS Longline Survey in its 50-year history, a 13' 2.5" female tiger shark.
Some of the study’s early work contributed to raising alarm about shark overfishing, which led to the establishment of various U.S. shark conservation measures in the 1990s. Excitingly, in certain species. “At least in the Southeastern United States, some shark populations are recovering. We’re seeing some signs of improvement,” Dr. Latour said.
So far, the program has caught over 8,000 sharks. Once the VIMS research team catches the sharks, a variety of measurements and samples are collected and shared with colleagues around the world. One studied sandbar shark was caught in 1996 and recaptured in 2023, which remains the world record for a recapture of a tagged shark. The biggest individual shark they’ve caught was a 13-foot tiger shark!
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Courtesy Ben DavisAfter a full workup, sharks are outfitted with tags before being released. Later recapture reports by anglers will provide information about the individual shark’s movement and growth rate.
To celebrate their 50th anniversary, the VIMS shark program released a free online app that lets anyone explore their data. You can also learn more about the program’s history in this YouTube video, and you can follow them on Instagram.
