By the Skin of Its Teeth

As recently as 50 years ago, the smalltooth sawfish was a common sight in coastal Florida waters. And what a sight! At a length of 18 feet or more, looking like a cross between a shark and a hedgetrimmer, it must've fueled many a fantastic fish tale, back in the day.

 

 

A release in progress at the Naples Pier.

You might think a creature this weirdly primitive looking was, in fact, primitive—a Jurassic throwback, forgotten by time and neglected by evolution. But according to the fossil record the sawfish was something of a late bloomer. The earliest known specimens date back only 56 million years to the Eocene epoch, concurrent with the first horses and whales.

 

Despite its sharklike appearance, a number of anatomical features—like gills on the bottom rather than the sides— serve to define it as a ray.

 

(A few species of “sawsharks” add to the confusion. These rare sharks also have a toothed snout, but their gills are on their sides, and they're much smaller, about five feet long at most.)

 

There are seven species of sawfish distributed worldwide. Only one, the smalltooth, makes its living in Florida waters. The other North American species, the largetooth sawfish, is found off the coast of Texas, and as far south as Brazil. Although their ranges overlapped historically, the two species are now separated by many hundreds of miles.

 

The sawfish's long, flat saw, or “rostrum”, is studded with sharp teeth on either side, some 25 to 32 pairs in all. If the teeth break, they're not replaced, as they are on sawsharks. An adult sawfish's saw may be five feet long or more. It's mostly used to disable smaller prey. The sawfish hunts by lunging into schooling fish—mullet, for instance—and slashing back and forth with its saw. Stunned and wounded fish are then sucked into its mouth. Because its mouth lacks sharp teeth, a sawfish can't tear chunks from its prey like a shark does. It has to feed on fish small enough to swallow.

 

It also uses its saw to stir up the bottom and flush out fish and crustaceans lurking in the sediment. The surface of the saw is covered with a network of sensors, tiny pores that enable the sawfish to detect minute charges of electrical current given off by hidden prey.

 

While the saw is a useful hunting tool, it's been the sawfish's undoing.

 



It gets tangled in nets, and is nearly impossible to extricate without harming the fish. As a result, various forms of commercial net-fishing, like shrimp trawling and gill netting, have decimated the smalltooth sawfish population over the last six decades, causing its range to shrink from the whole of the U. S. Gulf Coast and the entire Eastern Seaboard, to the relatively isolated and protected waters in and around Florida Bay. Fortunately, Florida's gillnet ban of 1995 has prevented a great many entanglements. Other fishing, pollution and habitat loss from coastal development have to a lesser extent also negatively impacted the smalltooth's population. Although they once numbered in the millions, some scientists estimate that no more than a few thousand survive today.

 

While the intimate details of its life cycle are shrouded in mystery, marine biologists have pieced together a pretty fair overview. Sawfish are euryhaline, meaning they can tolerate wide ranges in salinity. Although larger adults seem to prefer deeper waters offshore, pregnant females migrate into the estuaries every couple of years to give birth. Newborn sawfish pups are about two feet long. The number of pups in an average litter is believed to be eight, but varies with the size of the mother. At birth, the pup's rostrums are six inches in length and covered by a soft sheath, which keeps the mother from being cut.

 

In the estuaries, the pups move with the tides, sheltering in the grassbeds and among the mangrove prop roots, venturing farther offshore and into deeper waters as they grow. By the time they're about 10 feet long, they're sexually mature and may then begin to breed.

 

In 1999, in response to the alarming decline in the smalltooth's population, Mote Marine Laboratory inaugurated its Sawfish Conservation Biology Research Project. Dr. Colin Simpfendorfer, a senior scientist at Mote, began gathering information for a conservation effort that may well have saved the species from further decline. Simpfendorfer spent countless hours collecting anecdotal information from fishermen, analyzing data from sightings and tags, and developing statistical models for use by other agencies. A large part of his time was also spent in the field, hunting for sawfish in the muddy channels and brackish backwaters of Florida Bay. Despite their rarity, Simpfendorfer has examined and tagged 50 fish over the last five years.

 

 

Sawfish big and small are protected and must be released. Anglers who sight them are requested to call the swafish hotline.

On June 23, 1999, the National Marine Fisheries Service (NMFS) designated the smalltooth sawfish as a candidate for Endangered Species status. After almost four years of review, based in part on the work of Simpfendorfer, the smalltooth sawfish became the first marine fish granted Endangered Species status in U.S. waters. It's now afforded the same protection as manatees and bald eagles.

 

Meanwhile, marine biologists continue to gather information. Although it's too early to tell, the

y're cautiously optimistic. So far, at least, the smalltooth sawfish seems to be holding its own.

FS

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