Coastal Scientist Finds Large Shark Populations Are Taking A Dive

Oct 24, 2014

Tiger shark caught in 2008

The population of large sharks have dropped significantly since the 1980s, posing a serious concern for fisheries and ecosystem management.  This week on the Down East Journal, we speak to Coastal Scientist Dr. Joel Fodrie about his award winning research and the impact the decline of large sharks is having off the coast of North Carolina.  

On October 9th, beachgoers at Cape Lookout were shocked when more than a hundred brown and sandbar sharks went into a feeding frenzy just feet away from where they were standing.  Fortunately, Donnie Griggs who frequents Cape Lookout was filming and later it was posted to YouTube by Brian Recker.  The video went viral.  It’s received over 5 million views and captured media attention around the country.   Assistant Professor of Fisheries Ecology Dr. Joel Fodrie has seen the video and says this time of year, Cape Lookout is popular feeding ground for sharks.

"This happened to be an amazing convergence of food and the sharks to whip them into a frenzy.  I hope that people are just impressed by what nature has to offer to enrich our lives here on the coast.”

Tiger shark caught in 2001

While populations of small sharks, like the ones seen in the video are plentiful, it’s becoming increasingly rare to catch large sharks off the coast of North Carolina and elsewhere. Dr. Fodrie observed a significant decline in the number of large shark species over the past three decades using data from fishing tournaments in the Gulf of Mexico since the early 20th century. 

“When all three statewide tournaments that we collected data from, shark sizes increased from the early 1920s and 30s all the way up to the 1980s. And in the mid-1980s the size of sharks that were winning these tournaments declined rapidly and for the last 30 years, the size of sharks winning these tournaments are about one quarter the size of the sharks that won in the 70s and 80s.”

At one time, the large sharks in the Gulf weighed in at nearly 900 pounds and were 10-15 feet in length.  Now the sharks that are caught are typically 250 pounds and seven to eight feet long.  According to Dr. Fodrie, the commercial fishing industry started ramping up off the Gulf Coast during the late 1970s and in less than a decade, annual weight landing numbers dropped and recreational fishing numbers charted a decline in the size of large sharks caught during tournaments.  Dr. Fodrie was surprised to discover how quickly large shark numbers began to dwindle.

"We learned that these shark populations are very susceptible to overfishing. They tend to be longer lived, they tend to have low reproductive rates, long population doubling times.  So I think it gives us an idea on how sensitive they are to the stress of fishing at too high a rate.”

The first 60 years of the tournaments, huge bull sharks and tiger sharks predominated the winner boards.  But a shift occurred in the 1990s and Dr. Fodrie says the species of sharks winning the tournaments changed to hammerheads, blacktips, and much smaller than average bull sharks. 

Tiger shark caught in 1990

“In the last ten years, sometimes a 225 lb shark will win the tournament, and that’s a big fish, it’s a fish that would scare me out of the water.  And there are pictures in papers of kids just in awe of these fish.  And what those kids don’t realize and what I didn’t appreciate as much is just thirty years ago, there were fish four times that size.  There were literally fish that could bite that 225 lb fish in half. I think it gives us some perspective on what the ocean could sustain.  And it gives us a goal and it gives us a marker when we see that size fish regularly, we’ll know the system is at one point or that we still have some ways to go.”

Bull sharks, one of the species that Dr. Fodrie found documented in tournament records, can be found locally in the sounds of eastern North Carolina and can grow up to 10 1/2 feet.  Tiger sharks, which are found offshore, can reach 12 feet in length.  But it’s rare to find sharks that large off our coast. 

Tiger shark caught in 1988

 These big sharks play a key role in bringing balance to the ecosystem.  They feed on smaller sharks and stingrays, keeping populations in check.  Even though Dr. Fodrie’s study focused on the Gulf of Mexico, the decrease in large sharks also affects North Carolina’s coast.

“One well published example is, in losing the large coastal sharks, things like cow nosed ray populations have exploded.  Cow nosed rays eat scallops and now we see an additional challenge to maintain our scallops in the state of North Carolina.”

Dr. Joel Fodrie recently won "Best Paper of 2013" from the American Fisheries Society for his research on the decline of large sharks.  To see photographs of the massive fish caught in Gulf Coast tournaments, visit our website, publicradioeast.org. 

Credit: YouTube/Brian Recker