In January 2024, Jenny Staletovich was kayaking through Florida’s Lower Keys when she saw a worrying sight. A smalltooth sawfish was flapping erratically in the mangroves, almost like it was possessed. Five days later, it was dead. And for people in Florida, this was becoming a worryingly common sight. Ever since November, people had spotted the usually docile fish writhing and swimming in aimless circles before spiraling down to the seafloor, never to be seen again. What was going on? Let's investigate what’s been killing these endangered sawfish, and other sea animals around the world.
Sawfish Turning Up Dead In Florida Waters
Before we get into the real juicy stuff, you need to know a little about sawfish. They come in five species: dwarf, largetooth, green, knifetooth, and smalltooth. All five are big, but some species reach a whopping 23 ft - that’s longer than a great white shark! Their name comes from those massive blade-like hooters they have, known as rostrums, which they use to sense and stun prey as well as defend themselves against predators like sharks and crocodiles.
But back in 2024, smalltooth sawfish in the Florida Keys had far bigger problems than sharks and crocs. There were over 100 reported cases of them mysteriously thrashing about in the water, with 54 giving up the ghost entirely by July of that year. These mysterious events couldn’t have come at a worse time. The species is severely endangered, with only 450 females alive in the sea today, and we’re the culprits! Accidental capture in fishing nets and the relentless destruction of their habitat has left them in a very bad way. As a result, sawfish were the first fish species to be listed under the USA’s Endangered Species Act in 2004, which granted them special protections. These conservation efforts had led to a healthy bump in their numbers, until this disaster hit.
And it’s not just sawfish who were kicking the bucket. In the fall of 2023, divers and fishermen in the Keys spotted around 40 other species of fish, like snapper, snook, and grouper, all showing off this crazy behavior before swimming down to their doom too. It was like some kind of fish-pocalypse!
Things got so bad that it started to affect people’s livelihoods. Panicking health officials warned Florida residents not to eat any fish that had been taken from waters where infected animals had been found. Meanwhile, fishing guides had their trips cancelled by worried tourists fearing they’d be poisoned. Yet, nobody knew what the heck was going on. By April 2024, enough was enough. Scientists launched an emergency effort to help the endangered smalltooth sawfish. Good citizens were encouraged to report any sightings of spinning animals to the Florida Fish and Wildlife Conservation hotline, a kind of 911 for sawfish. When one was reported, a team would travel by boat to try and catch the sick animal. Then they’d take its measurements and blood samples, and tag it so if it lived it could be traced. On April 5th, the first proper rescue was attempted when a poorly 11 ft sawfish was spotted in Cudjoe Bay. The specimen was whisked away to the Mote Marine Laboratory in Sarasota. There, it was treated and monitored, with hopes that it could be released back into the wild. Unfortunately, despite showing some signs of recovery and receiving round the clock care, the animal’s condition worsened and it sadly passed 20 days later.
Indeed, the mass mortality of an endangered species like this had never been witnessed in recorded history. In response, in July the state of Florida gave up $2 million to fund research. At this point, there was massive pressure on scientists to quickly come up with an answer. One ecologist called Ross Boucek stated, the enigma was like having: “a final exam you forgot about and never studied before, and you have two hours to learn everything.”
To find out what was causing this crazy conundrum once and for all, scientists dove into the middle of the Keys and collected samples of water and sea plants, checking things like oxygen levels, pH, temperature, bacteria, pollutants, and chemicals. But after all this painstaking research, they found nothing! At least, not anything definitive. But that’s not to say they didn’t uncover some fiendishly compelling hints that could point us to the answer to this enigma.
Theories
One of the first leading theories was something called red tide. This strange natural phenomenon occurs when certain species of algae grow uncontrollably, producing harmful toxins that can decimate marine life. There are over 300 species of red tide algae, and despite the name they can change the water to all sorts of colors, including green, orange, and red.
Guess where these little blighters reside? That’s right, the Gulf of Mexico, right by the Florida Keys! More specifically, a toxic algae species called Karenia brevis lives in the water all year round at low concentrations. But when conditions such as temperature, nutrient levels, and wind are just right, Karenia flourishes, which is not good. The algae produces a potent neurotoxin called brevotoxin, which damages nerve cells and could well cause the sawfish to lose their sense of direction and end up in that wild death spin.
Red tide can happen naturally, with evidence showing that pre-Columbian Americans knew of the toxic bloom. However, in recent years, it’s become a far too common sight across North America due to warmer seas because of climate change and another process called
eutrophication. In farming, the land is spread with nutrients to bolster crop growth. However, when rain comes, it can wash these sprays into natural waterways, where they boost algae growth instead. Excessive algae growth depletes oxygen levels, and when the plants rot, they release carbon dioxide, lowering the pH of seawater and causing ocean acidification. And if you know acid, you know it ain’t good to swim in. In America, a worrying 65% of waterways have been harmed by the eutrophication process.
Just take a look at the
case of the Florida manatees, these cute blobby mammals enjoy munching on sea grass and being generally chill. But back in 2021, over 1,000 of them perished from algal bloom. Fertilizer runoff and wastewater leaked into their lagoons, leading algae to grow on top of the water’s surface, blocking out the sunlight and stumping sea grass growth.
Two years later in 2023, the same year fish started exhibiting that strange behavior, 77,000 acres of seagrass was lost to eutrophication, leaving many manatees starving. Poor guys!And in 2024, ramblers in Kauritutahi, New Zealand, stumbled upon
3,500 lifeless eels. These juvenile eels, or elvers, migrate upstream between late November and early March. They rely on a healthy stream flow and thrive when water temperatures range between 60 and 64°F. Can you guess what they found in the water? That’s right, algae, indicating the water was warmer than usual, a sign of climate change. What’s more, most of the stream had either very limited or no water flow. This all has a knock-on effect: lower stream flow leads to a reduction in oxygen and increase in toxins, both of which are made worse by rising water temperatures and algal blooms. Limited water flow clearly isn’t a problem in the Gulf of Mexico, but rising water temperatures and algal blooms could be. Something which is supported by an astonishing discovery made by paleontologists back in 2010.That year they unearthed
Cerro Ballena, a mind-blowing graveyard of prehistoric sea creatures in Chile’s Atacama Desert. After a year of digging through four separate layers of rock, they uncovered fossils from ten different species dating back to the late Miocene around 5 to 11 million years ago.
The site holds the densest cluster of extinct marine mammals anywhere in the world, including the skeletons of more than 40 large baleen whales. Why, the very name Cerro Ballena is Spanish for whale hill!
Among the more bizarre species found were aquatic sloths, big bear-sized beasts, more used to wallowing than climbing trees, and a walrus whale, a cross between a walrus and a whale, complete with a tusk over 4 ft long. But what’s most intriguing about this find are some strange orange patches on the animals’ bones, which could be the remains of toxic algae.
These blooms likely poisoned the animals of Cerro Ballena after they ate contaminated prey or inhaled the deadly toxins, leading to their premature demise. Their bodies then sank to the seabed, where they were buried in years of sediment. And this didn’t just happen once! The four different layers of fossils show that the same event happened four separate times across a period of 10,000 to 16,000 years. So, this algae’s been a problem for a long time.And with all that in mind, let’s round back to those sawfish. Surely algae’s to blame? Dr. Michael Parsons, from Florida Gulf Coast University, certainly thinks so. As well as some fish showing signs of recovery after being placed in untainted water, scientists found that as the tide shifts, the fish often regain their normal behavior. Some in as little as 25 minutes! And that’s not all. Researchers also noticed that fish tend to recover if pulled up from the deeper waters, where toxin levels are much higher. Sawfish are bottom dwellers and would be much more vulnerable to these toxins. There’s just one problem with this, after taking samples of the water, scientists didn’t detect particularly high Karena level, the algae most common to the Gulf of Mexico. They did detect high levels of an algae called Gambierdiscus though. This is usually harmless, but high concentrations can be deadly. 2 pints of Keys seawater usually contains 30 to 40 Gambierdiscus cells; these recent samples showed a gargantuan 1,000!
What’s more, some species of Gambierdiscus produce ciguatoxins, a complex potent neurotoxin that can build up to dangerous levels in coral reef fish. If a person ate fish contaminated with ciguatoxins they’d catch ciguatera, a nasty illness that invokes lots of vomiting, diarrhea and nausea. Likewise, fish would suffer from neurological problems, like hyperactivity and twitching. Sound familiar? Yes, the death spirals observed in sawfish might be a similar reaction, triggered by neurotoxins attacking their nervous systems. Adding more fuel to this theory, ciguatera is much more common in reefs that have suffered environmental damage, like warming waters and pollution. Well, during World War II, bombs destroyed reefs across the Pacific Islands, the stress of which caused a ciguatera outbreak that left many civilians sick.
While there’s been no bomb dropping on Florida lately, heat could certainly have played a part. In the summer of 2023, Florida’s temperatures approached record highs, hitting 100 degrees Fahrenheit! That’s got to be it then, right? It was all because of ciguatoxins! Well, no. There’s just one problem with the ciguatera theory. If it really was behind the sawfish casualties, humans would be getting sick from eating contaminated fish, but they’re not. Instead, laboratory tests revealed there was a cocktail of toxins in the water left by different species of algae, any one of which could be behind it all. So, after all that we don’t even know which algae caused it?! This is a real head scratcher.
Thankfully, since July 2024, the mass die-offs seem to have mostly stopped, though no one’s quite sure if the bizarre illness will come back. From what I can tell, we need to shoulder a lot of the blame for putting these animals, and ourselves, at risk. The rising water temperatures that led to this toxic algae thriving can certainly be attributed to our impact on the environment. But the sawfish calamity isn’t the only thing hitting our marine life. It turns out that sea dwelling animals around the world have been devastated by strange human-related causes.
Stranded Whales
We’ve all heard the phrase having a whale of a time, but lately, whales aren't having much fun at all. Just go back to 2022, where a jaw dropping 230 pilot whales mysteriously washed up on the shore of Macquarie Harbor in Tasmania, Australia.
While a few were saved, the
majority sadly perished and local farmers had to tow the animals out to sea to be munched on by scavengers. And that’s not all. Since 2017, over 500 minke and humpback whales have been seriously injured, stranded, or killed along North America’s East Coast. So what’s to blame for this tragedy? Critics of offshore wind farms blame seismic surveys. Before building the windfarms, the area must be mapped by sending tremendously loud sound pulses through the water known as seismic surveys. Some people argue the noise pollution from these disturbs whales, who rely heavily on sound, and essentially causes them to freak out. However, scientists have dismissed this as a load of boloney. The Bureau of Ocean Energy Management say their surveys only generate sound levels around 220 decibels. That’s a lot quieter than the 250-decibel seismic air guns used for oil and gas exploration. Truth be told, even if whales were disturbed by wind farms, they’d just swim away. So, what’s the deal? Well, more likely culprits are marine traffic, industrial fishing, microplastics, and good ol’ plastic pollution. In 2018, a sperm whale was found on a beach in Indonesia with over
13 pounds of plastic in its stomach, including 115 cups, 25 plastic bags, two flip-flops, and more than 1,000 pieces of string.
Dead Whale Found With 13 Pounds of Plastic in Stomach | National Geographic by National Geographic Imagine carrying all that garbage in your guts! That’s awful. And chances are, it’s not even the worst case. Of all the whales that have been beached on America’s East Coast from 2016 to 2023, only half could be autopsied due to the massive scale of the task, because whales are big. Among those examined, 40% had been struck by ships or entangled in fishing gear. Yet no single, fixable cause has been identified. So, it’s probably a whole myriad of reasons. If you want to investigate more, we've got a whole article about the reason why
whales are escaping the ocean.
Dolphins Wash Up Dead On Beach
As the ocean’s temperature increases, diseases that once struggled to survive in the cold water begin to thrive, and can bring devastating consequences for marine life. Between 2013 and 2015, the bodies of 1,600 dolphins washed up on East Coast beaches, all the way from Florida up to New York.
But that’s just a fraction of the 20,000 estimated to have died in total, reducing the region’s population by a catastrophic 50%. And of all the dolphins’ bodies studied, 92% were
cetacean morbillivirus positive. This dangerous pathogen is comparative to human measles and has been flourishing since climate change heated up the ocean along the East Coast. Ill dolphins can suffer from infections of the lungs and brain, as well as nasty sores that sprout all over their bodies. When you think of dolphins, you probably imagine them happily prancing out of the water. They do this not only to catch a breath, but to strengthen friendships. Sadly, it’s during these moments of joy that they can infect each other. If two dolphins jump out of the water next to each other, a healthy dolphin might inhale the virus particles exhaled by a sick one, and if they touch it can be passed on by wounds. A pregnant dolphin can even pass it to her unborn calf.
The two year outbreak in 2013 was the worst on record, but far from the only one. Between June 1987 and May 1988 another occurred, which claimed the lives of 900 dolphins. The one silver lining is that the animals that survived this outbreak would’ve developed antibodies against the virus, stopping them getting sick again. These immune dolphins also helped shield other dolphins, since they’re less likely to come in contact with an infected animal, a phenomenon called
herd immunity. But eventually, these virus-resistant dolphins will die off or move away, leaving younger generations vulnerable to the disease once more. It’s a vicious cycle, and one without an obvious solution.
Fibropapillomatosis And Turtles
If you thought it was gonna get any chirpier, you’re in for an unpleasant surprise. Turtles are next up, and they’ve arguably had it worse than dolphins. Some turtles, especially green turtles in US waters, have been affected by a truly terrible disease, fibropapillomatosis, also known by the much easier to pronounce initialism FP. This illness causes tumors to mushroom all over their bodies and even their organs!
Free diving in Hawaii & saw a green sea turtle w/ Fibropapillomatosis. Conservation is #1 priority. by sarah lopez FP can be mild for some turtles, and up to 60% will see their tumors shrink over time. But for others, it can be seriously debilitating, causing blindness, internal damage, and even death. FP’s discovery dates back to the 1800s, though it was only in the 1980s that it gained attention after green turtles in the USA were spotted with it. So, how is this sucker spread? Well, the disease is a type of herpesvirus that’s spread through contact with other turtles or from swimming in contaminated waters though other nasty stuff like pollution might cause tumors too. FP has also been found in leeches that cling to marine animals and lap up their blood, so it may be these little vampires play a part too. What we do know is that young sea turtles catch FP when they make their first visit to shallow feeding waters after spending their first few years out at sea.
So, can anything be done? Help is out there for infected turtles, but typically only if they become stranded on land. Once found, they can be taken to the vets to have their tumors surgically removed and receive treatment. Whilst this may help a handful of turtles though, there’s currently little to be done for the majority of sufferers since FP isn’t fully understood yet. So, if you ever see of one of these poor animals stranded with the illness, look online to find your nearest stranding network and report it, that way, you’ll be turtley awesome!
Seabirds
When we think of sea life, we often focus on the creatures swimming below the surface, but what about those soaring above? Sadly, some seabirds are facing real dangers. The UK is a special place for two such species: the great skua and northern gannet, with Britain’s shores home to most of the world’s nesting skuas and half of the world’s gannets.
In 2021, a
worldwide outbreak of H5N1, a variant of bird flu, wiped out a calamitous 75% of skuas and 25% of gannets across the UK. And by June 2022, Bass Rock, Scotland, which used to turn white from its millions of nesting gannets, had lost a quarter of its birds to this nasty flu. The poor avians suffer from a lack of appetite, breathing struggles, and diarrhea, before it eventually takes them out entirely.
Northern Gannet affected by avian influenza, Foula, summer 2022 by Kees Camphuysen And yes, the outbreak has been linked to rising temperatures. In North America, warmer winters and early springs could’ve been helping some moisture-loving bacteria to spread more easily. Meanwhile, wetter weather can help the flu stay alive in bird droppings and contaminated water. Despite what the name implies, the flu can infect other animals too, including us! It’s not all bad news though. The gannet population seemed to show some recovery in the summer of 2023. You can even spot the survivors, after recovering from the flu, their bright blue irises turn weirdly black. Scientists aren’t sure why yet, maybe they need a bird’s eye view.
Sea Lice In Salmon Farms
We all love some tasty pink salmon. In 2022, the global supply of Atlantic salmon was over 3 million tons. But you might not be so keen on it after learning about the problem plaguing farmed salmon right now. Growing on their skin are parasites called sea lice, tiny crustaceans less than 0.03 inches long that latch onto them and feast on their blood and flesh. They coat the salmons’ bodies in sores that weaken their immune system, and in severe cases, can cause mass die-offs.
So, what’s caused this horrific plague? Well, tiny sea lice larvae need to find a host to survive, which is tough when you live in the wide-open seas. But on farms, where salmon are crammed together in unnaturally high numbers, it’s a piece of fishcake. And just like with humans, diseases and parasites spread much more easily through high density populations. All this is obviously a huge headache for farmers, since infected fish can’t be sold. The only known treatments are chemicals, but these can stunt the salmon’s growth. Plus, lice have developed resistance to the most commonly used ones. Since sea lice tend to hang out near the surface, keeping the fish in deeper water helps. But you can’t fully cover the pens because salmon need to pop up to the surface to refill their swim bladders for buoyancy. To get around this, farmers have started using snorkel cages. These have net roofs set 30 to 65 feet deep, keeping the salmon away from the surface waters where lice larvae hang out. The cages also have a sealed snorkel tube in the middle, so the salmon can swim up to the surface to get air without being exposed.
Pretty clever, right? These snorkel cages help reduce infection by 75%, but they’re still not perfect. The biggest concern is that the lice could spread to wild salmon migrating past the fish farms.
