Disappearing Fish
What Happened to the Smalltooth Sawfish and Grouper?
Not much is known about the smalltooth sawfish and that's one reason the odd-looking fish became in 2003 the first marine fish in U.S. history to make the Endangered Species list.
The smalltooth sawfish is frequently mistaken for anything from sawsharks and hammerheads to swordfish. Because they rarely end up on a dinner plate, no one until fairly recently noticed they almost went extinct.
Smalltooth sawfish were once so common, inhabiting coastal regions from New York to Texas, that they were considered a nuisance. Decades, if not a century, of careless exploitation and habitat destruction reduced their numbers by more than 95 percent. In the U.S., they now only remain in spots off of the Atlantic and Gulf coasts of Florida.
The smalltooth sawfish is one of seven types of sawfish that exist throughout the world. All seven are listed as "critically endangered" by the World Conservation Union.
Its movements mimic those of its relative the shark; but sawfish are actually a type of ray. Like other rays, the smalltooth sawfish mature very slowly and produce fewer offspring than other fish. They reach sexual maturity after approximately 10 years and give birth to only six to eight pups every other year. They are difficult to replace. Scientists project that it could take up to 100 years before the smalltooth sawfish are back to sustainable numbers.
The loss of habitat due to human activity and development along the Florida coast has contributed to their decline. As adults, smalltooth sawfish can occur in a range of tropical or sub-tropical habitats. Their giant size, 16-to-24 feet, prevents them from confronting many predators.
The small, juvenile sawfish depend on the shallow water around mangroves and seagrass beds for protection from sharks and crocodiles as well as for food. Seagrass beds provide a habitat for hundreds of species, including many of the juvenile sawfish' main dietary needs such as crabs, shrimp and small fish. The seagrass leaves are especially important for crabs, which feed on the leaves.
"Boaters will run across the flats and destroy the seagrass," said Rob Clifton, a senior marine outreach coordinator for the Audubon Society. "It's all connected. If you're missing one of those, you're missing a link in the ecology chain."
The primary factor in their precipitous decline was overfishing, intentional as well as unintentional. Despite state protections in Florida and Louisiana that beginning in 1992 outlawed catching or possessing a sawfish, federal protection was not enacted until 2003.
Commercial fishermen did not specifically target the sawfish, but the use of gillnets contributed to huge numbers being caught and eventually killed as bycatch. Its long saw, or rostrum, easily became tangled in the nets. Florida banned gillnets in 1994, but the damage had already been done. Over time the snout became a trophy of sorts and a trend emerged where people would cut it off and throw the rest of the sawfish back in the water. At one point, saws were selling on eBay for more than $1,000.
The rostrum, which can reach five feet, protects the sawfish from potential threats, but mainly helps it catch food. The sawfish will slash its saw from side to side in schools of fish, attempting to lodge a fish on its rostral teeth. It will also use its saw to disturb the mud to unearth crabs and other food.
Matthew McDavitt, a former anthropologist and now a practicing attorney in Virginia, spent a decade writing a report on the international sawfish trade. His research eventually led to eBay's banning sales of smalltooth sawfish on the Web site, and helped secure protection for the sawfish under the Convention on International Trade in Endangered Species. In April, he received the prestigious Peter Benchley Shark Conservation Award, which honors those who work to protect sharks.
McDavitt first became interested in sawfish as an undergraduate at the University of Virginia, where he wrote his senior thesis on Aztec art and iconography. Although it is uncommon in western culture, the sawfish has been a religious and cultural symbol throughout the rest of the world.
"You find dozens of [sawfish rostra] buried under the main temple, which is the center of the Aztec world in the middle of Mexico City," he said.
The Aztecs believed that the world had been created from a gigantic carnivorous animal called Cipactli. Although it is represented mostly as a crocodile, Cipactli has shifting animal attributes that include depictions of sharks and sawfish. According to the Aztecs, when the gods were forming the world, they wrestled the monster Cipactli, eventually ripping the monster in half. The lower portion of its body formed the earth, the upper half the heavens.
One of the motives behind human sacrifice, McDavitt said, was the desire to feed this "earth-monster" human hearts and blood, which were believed to be the substances of the universe that contained the most life force.
"If you wanted [Cipactli] to grow crops and make good weather, you had to release more energy," he said. "You had to drain human blood back on to the earth in order to feed this earth-monster."
McDavitt believes the sawfish snouts found under the temple were associated with warfare and represent the Aztecs' duty to feed the earth with blood and bodies so the earth would provide sustenance for mankind.
"What the Aztecs did is, not only did they have conquests, but even among their allies they had wars that were ritual," he said. "The whole purpose of being captive [was] to feed the two main forces of the universe, which is the sun and the earth. And so as these warriors hit each other with these glass-edged swords, the blood would drain on to the ground and that would feed the earth monster."
Despite the symbolic and historical significance of the fish, scientific studies addressing their depletion developed only recently. McDavitt is optimistic because public awareness continues to grow.
"My grandparents continue to send me articles on swordfish, even though they are well-aware of what I study," McDavitt said, bemoaning the lack of past interest in the sawfish while remaining upbeat about the future.
"We don't know what the ecological impact [of their depletion] is, but I think that luckily for sawfish they're very charismatic so they can generate the same sort of fervor that a great white or panda bear can generate."
The Grouper
The decidedly uncharismatic, but friendly and delectable grouper, could hardly be more different from the sawfish, though both fish face possible extinction.
Grouper have been known to change sex, exhibit territorial behavior, live up to 50 years, spawn by moonlight in groups of more than a thousand, and, if feeling unthreatened, approach and allow people to pet them.
All these attributes make certain species of grouper fascinating to study, but the same traits make them especially vulnerable to extinction.
Twenty of the world's 162 species of grouper are currently listed as endangered in varying degrees, on the "Red List" of the International Union for the Conservation of Nature. Two of the most threatened populations exist off the coast of Florida and throughout the Caribbean: the goliath grouper and the Nassau grouper.
Goliath grouper are the largest of the grouper species in the western Atlantic. At measurements approaching eight feet and weights of over 800 pounds, they are big enough to swallow you.
The largest goliath grouper ever caught in Florida waters, according to the Florida Fish and Wildlife Conservation Commission, was 680 pounds. Their size made them a coveted prize for recreational as well as commercial fishermen, who in past years would easily catch thousands of pounds of the highly desirable grouper in one outing.
Compound fishing pressure with the grouper's biological quirks and the fish suffered a sharp decline in the 1980s and '90s, when regulations were adopted by a federal agency to make fishing and harvesting goliath and Nassau grouper illegal. The legislation remains in effect today.
The goliath grouper's large size and life span contributes to its vulnerability because of the time it takes for them to develop and reach sexual maturity. Males do not reach sexual maturity until they are about 5 or 6 years of age and approximately 3 1/2 feet; females take longer at 7 years of age and a bit over 4 feet. The larger the fish, the more sperm or eggs he or she produces.
Many are caught, however, long before they measure 4 feet and have the chance to reproduce.
Those that reach sexual maturity travel several times a year, usually during the summer months, to very specific sites to form spawning aggregations. Unlike other fish that mate the entire year, grouper spawn in a very specific place and time, almost always during the full moon.
Historical numbers of goliath grouper aggregations comprised more than 100 individuals, increasing the likelihood of fertilized eggs. Heavy exploitation followed as fishermen discovered the aggregations and caught many, many fish per outing, consequently wiping out an entire generation of reproductive grouper. Fishermen returned year after year until aggregations disappeared or were no longer commercially viable. Some consisted of numbers as low as 10 fish per site.
Another attribute that makes the grouper particularly vulnerable is a curiosity about humans.
"Goliath groupers tend to be very curious, and if you're underwater working they'll come sit and watch you," said Vanessa McDonough, fishery and wildlife biologist for Biscayne National Park. "They might be accustomed to people just being there and perhaps being fed. So they don't recognize people as something to fear so much as a source of food."
Leslie Whaylen, a reef fish specialist and founder of the Grouper Moon Project, calls grouper the "puppy dogs of the sea."
"A lot of divers like to dive with them under water; some of these grouper swim right up to you," she said.
She recalls the story of Ben, a famous grouper in the Cayman Islands.
"He would come up to divers and want to be petted," she said. "Groupers are like the puppy dogs of the sea and not too many people really relate that. They just see grouper filet sandwich on menus everywhere in South Florida."
The curiosity of the grouper makes it much easier for spearfishermen to approach the fish. Yet like any animal, the grouper adapts to its environment.
"If you go to a reef that has been heavily spearfished, I guarantee the minute a fish sees you, it's going to jet the other way," said McDonough.
Many other groupers share some of the challenges facing the goliath grouper such as limited habitat, limited time in which to spawn, and a vulnerability to over-fishing. The population of the Nassau grouper has been severely impacted by the fishing industry and is listed as a "species of concern" by the National Oceanic and Atmospheric Administration. A "species of concern" is any species about which the NOAA Fisheries Service has concerns regarding its status and threats. The fish is also listed as "endangered" by the IUCN.
A Nassau grouper spawns several times during the year and their aggregations are historically much larger than those of the goliath grouper. Research conducted in the '70s shows that Nassau grouper aggregations contained up to 100,000 fish. Yet due to exploitation, very few aggregations remain. In the Caribbean, according to Whaylen, those that do remain support less than a thousand fish.
What differentiates the Nassau groupers from others of its species are the color alterations they exhibit while they mate. Called bicolor coloration, Nassau grouper have been documented changing colors up to 10 times in one minute. Instead of the normal striped pattern of brown and white, they become black on the top, white on the bottom, and develop a white streak through their eyes. They also change to predominantly white or dark. Each phase occurs at a different time of day and both males and females make the changes.
Like most groupers, Nassau groupers are hermaphrodites, switching from female to male, as they grow larger. (Goliath groupers are believed to make this switch, though scientists have not confirmed that yet.)
This sexual transition contributes to the grouper's vulnerability to over-fishing because if a disproportionate number of large fish are taken out of the population, it potentially skews the ratio of the larger males to the smaller females. Removing the larger males limits the chances of the fertilization of the eggs. In turn, the females will try to compensate by transitioning faster.
"The fish will compensate by changing sex earlier," said Whaylen. "But then you get smaller and smaller males which means less and less sperm output."
The importance of size also applies to females because the smaller the fish, the fewer eggs she produces. In addition, the amount of predation of fertilized eggs and juvenile fish stresses the need of high levels of reproduction.
"Fish do spawn quite a lot. But the percentage that actually makes it to even the small juvenile stage is less than one percent," said McDonough. "Even though a fish is capable of reproducing at a very high level, very, very few of what it produces will actually become a new fish."
A diminishing grouper population affects not only the grouper. As the fertilized eggs drift with the currents, many fish and invertebrates feed on the eggs. When groupers grow to be juveniles, many other fish depend on them as a food source. In turn, such predation significantly reduces the number of groupers that reach adulthood.
Although conservation efforts have aided in stabilizing the grouper populations in South Florida and the Caribbean, the grouper still faces significant challenges.
Destruction of the mangroves and coral reefs, on which many grouper depend, has had a deleterious effect on the fish' recovery. But for the goliath grouper, conservation efforts have paid off. In 2006, it was removed from NOAA's "species of concern" list. However, people are still prohibited from harvesting goliath groupers under the Magnuson-Stevens Conservation Act.
Nassau grouper are still listed as endangered, but Whaylen is optimistic. The efforts of the Grouper Moon Project have resulted in the protection of several aggregation sites in the Cayman Islands.
"Nassau groupers don't typically spawn till they're 4- to 7-years-old. And now in our sixth year of doing the project, the really small ones we see out there on the aggregation are probably the product of spawn that happened [the year we started Grouper Moon Project in 2001]," she said. "We've been able to protect the site and now we're getting to see the babies come back."
