Decades Long Survey Tracks Shark Populations Off NC Coast

Jul 13, 2018

Sharks are brought aboard, measured, tagged, and have a small fin clip taken for genetics research. Within a minute or two of being brought on board the animal is released back into the water.
Credit Mary Lide Parker/ UNC Research

One of the longest running shark surveys in the world is taking place off the coast of North Carolina.  For the past 45 years, researchers at the University of North Carolina’s Institute of Marine Sciences have been catching and tagging a variety of shark species in an effort to determine the health of the ocean and measure changes in shark populations.

“It provides us a really unique opportunity to study these sharks.  A lot of these sharks are long lived, they’re around for quite a while so it can take decades to really understand what their populations are doing and so that is one of the unique things about our survey.”

Martin Beneavides, a Ph.D. candidate at the University of North Carolina’s Institute of Marine Sciences in Morehead City heads up the offshore research trips which take place every two weeks between April and November.   

Credit Jared Brumbaugh

“I’m looking at two main things.  I want to look at seasonal patterns, how the sharks change throughout the year in terms of the number of sharks and the different types of sharks that are out here. And then I’m also looking at size changes within each shark species, whether sharks are getting smaller, getting larger, remaining the same.”

The surveys are conducted at locations two miles and seven miles off the coast of Shackleford Banks.  The crew aboard the M/V Capricorn assists the researchers with bating 100 hooks and attaching them a longline, which stretches for nearly a mile.  After the longline is allowed to “soak” in the water for an hour, the crew reels in the cable using a winch. 

“Any sharks caught get identified, tagged and released.  We of course take any data we can on them such as size, in some cases, we’ll take fin clips so we can use their DNA to try to figure out more specific details about them.”

The longline surveys collect information on about half of the more than 45 species of sharks that are found off our coast.  The most common shark they catch, Beneavides said, is the Atlantic sharpnose, which grows to be three feet in length.

Credit Jared Brumbaugh

“This shark is one that actually increased throughout the 45 years of the survey.  When we first started surveying the North Carolina shark populations, it was very rarely caught.  Maybe five individuals per year.  Now, we get, for example, on our last survey, we got over 15 of them in one set.”

As sharpnose sharks increase in population, data from the surveys shows blacknose shark numbers have been declining.  Researchers noticed a significant decrease in large bull and tiger sharks in the 70’s and 80’s due to overfishing.

“It should concern us if we see changes, especially negative changes and we should be trying to figure out what it is that is allowing for some of these populations to rebound so that we can put better regulations in place to allow us to have better regulations in place that will allow us to have healthier ocean ecosystems.”

During a shark survey on June 27th, a total of 25 sharks were caught, the highest daily catch in the study’s 45-year history.  A sign for optimism, Beneavides says, is that they’re starting to see some shark species that were declining making a comeback.

 “I think the state of shark populations is a good sort of pulse we can take of how the ocean is doing in general.” 

Credit Mary Lide Parker/ UNC Research

Credit E. Woodward, UNC Institute of Marine Sciences

Credit Mary Lide Parker/ UNC Research

Credit Jared Brumbaugh