Climate change could shift the kinds of fish swimming in your favorite childhood fishing hole – and maybe for the better.
Avid fisherman Mike Allen has his line out in the Gulf of Mexico for snook, a fish that wasn’t in his backyard 15 years ago. His sunglasses reflect a more tropical coastline in Cedar Key, filled with new organisms that now call the region home.
He puts snook in a new category emerging from climate change: a term experts have been calling “neo-natives.” In Florida and around the world, these organisms are native to a region but expanding to nearby areas because of climate shifts such as warmer temperatures or fewer hard freezes.
“It’s not like all the effects of climate change are bad,” said Allen, a fisheries professor and director of the University of Florida’s Nature Coast Biological Station in Cedar Key.
“Range shifts are happening all across flora and fauna,” said Allen, who recommends against calling such species “invasive.”
The federal government defines invasive species as “an alien species whose introduction does or is likely to cause economic or environmental harm, or harm to human health.” However, neo-native species are simply shifting to nearby areas because they can. They haven’t hitched a ride in ballast water or grown too large for a fish tank – they’ve just moved into a suitable new home because climate change made it possible.
In recent years, scientific papers and news reports have been filled with devastating stories about marine life such as coral reefs that are struggling to survive warming . But some marine species are taking special advantage of climate change, using waterways to quickly expand their ranges. The following species fall into the “neo-native” category – a list that will continue to expand as the world warms.
Snook
The pastel-colored and salty fishing town of Cedar Key is known for its clams and charm. Now, it’s got a game fish in its waters that Allen said wasn’t here 15 years ago.
Recreationally and economically, this is great news for Cedar Key. Increased tourism means more money for small businesses in the historic fishing village, and it gives residents a new fish to cast for.
Environmentally, though, it’s a different and more complex story.
Allen said the snook’s movement into the waters near Cedar Key will have implications for the food web, as the black-striped predators compete with red drum and spotted sea trout.
“Those negative effects we don’t fully understand,” said Allen.
While some fishermen might love that snook are in the waters now, Allen points out that a warming climate also means a higher risk of sea rise and increased storm intensity - which means more danger and costs for the people who call Cedar Key home.
However, some residents have started curating a neo-native species to help protect against the adverse effects of climate change. As more mangroves move into the area, people increasingly appreciate their benefits.
Mangroves
John Schleede, one of the island’s clam farmers, has known the mud-flat scent of a clam boat since he was eight years old. His family moved to Cedar Key 28 years ago to work in the clam business.
“Mother nature rules the roost in this game,” said Schleede, who’s been battling the fluctuating clam economy since Hurricane Idalia. But he’s got an additional natural defense against hurricanes and stronger storm surges: mangroves.
Schleede said if he had to keep one thing in front of his property, it would be mangroves. They hadn't always been there.
Julie Walker, a professor of biology and environmental studies at St. Mary’s College of Maryland, researches the effects of climate change on mangroves and how it has allowed them to sprawl along the north coast of Florida. She calls the salt-loving trees a “climate barometer” – crediting mangroves’ lack of cold tolerance for indicating when the last major freeze occurred.
The mild-warm climate of recent years has allowed them to move farther north than ever before, changing the ecosystem. Walker explained that as mangroves shift, they encroach into salt marshes and grasses that are more cold-tolerant, changing habitat structure.
In good news though, a study done by Walker shows that key species are adaptable to different landscapes introduced by mangroves.
“These mangroves indicate what is going on with our climate,” she said. They also attract other other neo-native species like the mangrove box jellyfish.
Mangrove Box Jellyfish
While the words “box jellyfish” might keep some people out of the water, biologist Angela Witmer assures that the much less dangerous mangrove box jelly has a mild sting it uses only to stun microorganisms.
Well-known Chironex fleckeri, the deadly box jellyfish that lives in Australia and elsewhere around the Pacific, is considered the most venomous marine animal, according to NOAA. The lesser-known box jelly moving north in Florida is Tripedalia cystophora, one of the smallest jellies in the world. An adult grows up to be about the size of a grape.
Witmer, an associate professor of biology and oceanography at Palm Beach Atlantic University, found the mangrove box jelly in the intracoastal near MacArthur Beach State Park in southeast Florida while conducting other research.
Originally from the Caribbean, the mangrove box jellyfish is one species that Witmer believes will “move with the mangroves.” However, the Caribbean jelly seems to mind its own business eating microorganisms called copepods and coexisting without harming the ecological balance.
“They haven’t appeared to have detrimental invasive qualities,” said Witmer, bolstering the case that these are “neo-native” rather than “invasive.” She explains their Florida success to their similar habitat in the Caribbean.
Witmer says one thing is for sure - we’ll start seeing them more because of climate change. They’ve made their way through John D. MacArthur Beach State Park, and now have been found as far north as Tampa Bay.
Roseate Spoonbill
Jerry Lorenz, state research director for Audubon Florida, has been studying birds for 35 years. In preparation for his retirement, he jokes that he will be able to continue to study the tropical roseate spoonbill when he returns to his home state of Kentucky.
Lorenz has been working in the Florida Keys since 1989 and was instrumental in recognizing the roseate spoonbill as an indicator species. An indicator species is a scientific term used to describe species that reflect the health of their surrounding environment.
The only places that spoonbills nested were Florida Bay in the Florida Keys and some off-coast Tampa Bay islands.
But now, Lorenz said, the spoonbill is moving northward with warmer temperatures.
Since 2005, spoonbills have moved beyond Tampa Bay, and in 2010 scientists like Lorenz started to notice more dramatic change. He said that because of the local 8-inch sea-level rise in Florida Bay, “the water doesn’t get low enough for spoonbills to effectively forage enough in the Florida Keys.”
There is good news though, for the spoonbills. Lorenz said they are doing great elsewhere in Florida and beyond, in states like Georgia, South Carolina, Arkansas, and North Carolina. He even mentioned a spoonbill sighting in Québec, Canada.
Mahi Mahi
Deep sea fishing charters may have to adopt a new approach to Mahi Mahi if they want to keep catching the beautiful blue-green game fish.
“Fishermen in South Florida aren’t catching Mahi Mahi the same way we used to,” said Lela Schlenker, a researcher specializing in pelagic fish; those that live in the open ocean.
“But North Carolina’s fishers are doing great with catching them,” she said - adding to the list of neo-native species expanding into northern waters.
Schlenker said that as temperatures warm, the icon of Florida menus and marine waters may spend less time in South Florida and remain deeper in the water column to keep cooler.
Her tagging data shows their movement is highly influenced by temperature. Temperature is a major driver for things like prey abundance and predator avoidance. It also helps determine how much dissolved oxygen is in the water. To maintain a comfortable environment, Mahi Mahi bump the thermostat by changing their depth.
However, marine organisms face an obstacle in adjusting to Florida’s temperatures. If a species lives on the Atlantic coast, it can move up the coast to find cooler water. But if it lives in the Gulf of Mexico, Schlenker said it may have to go south around the tip of Florida to move northward, adding to the challenges of ecosystem adaptation.
What Matters More?
With neo-natives moving about in our environment, species protection becomes more complicated.
A spoonbill does not emit a carbon footprint. Instead, it now struggles to find water shallow enough for its chicks to create their own tiny three-clawed footprint. But when that same spoonbill takes habitat and resources from another bird further north, which species should we prioritize to protect?
Understanding the impact of neo-native species and their role in climate change is ethically new for scientists and conservationists. Convincing a lucky fisherman that their favorite catch is moving to their fishing hole is no easy task. While the snook may be on the hook, the warming climate around them may hold more troubling challenges.