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Oil spill threatens iconic fish with saw-like snout

May 27, 2010
Courtesy of the University of Florida
and World Science staff

The oil spill caused by the col­lapse of a BP oil rig in the Gulf of Mex­i­co threat­ens to kill off a crit­ic­ally en­dan­gered saw­fish and its rel­a­tive, says a Uni­vers­ity of Flor­i­da sci­ent­ist.

The an­i­mals are the only two ma­rine fish in Un­ited States wa­ters to re­ceive such fed­er­al pro­tec­tion.

The largetooth sawfish. The oil spill caused by the col­lapse of a BP oil rig in the Gulf of Mex­i­co threat­ens the ex­ist­ence of this crit­ic­ally en­dan­gered animal, says a Uni­vers­ity of Flor­i­da re­search­er. (Image cour­tesy NOAA)

The large­tooth saw­fish, a pop­u­lar cu­ri­o item known for its saw­like snout, was pro­posed as a fed­er­ally en­dan­gered spe­cies on May 7, less than three weeks af­ter mas­sive amounts of oil started gush­ing in­to Gulf wa­ters, said the uni­vers­ity’s George Bur­gess.

“The oil spill will not only have very dire ef­fects on such highly vis­i­ble crea­tures as seabirds and dol­phins, but al­so threat­ens a mul­ti­tude of bot­tom-dwelling or­gan­isms in­clud­ing the small­tooth saw­fish, which al­ready is in con­si­der­able trou­ble as its range di­min­ished and its num­bers dwin­dled,” he said.

What’s left of the small­tooth saw­fish popula­t­ion is con­fined to the low­er pen­in­su­la of Flor­i­da, Bur­gess said, with the most im­por­tant ar­ea rang­ing from Char­lotte Har­bor through the Ten Thou­sand Is­lands ar­ea of the Ev­er­glades in­to Flor­i­da Bay and the Keys. That’s where the larg­est por­tion of its nurs­er­ies is found and these are now threat­ened by the oil spill, he said.

“As oil gets caught up in the loop cur­rent, it will be pulled down in­to the Gulf Stream, which goes right by Key West on its way up the U.S. East Coast,” Bur­gess said. “The op­por­tun­i­ties for se­ri­ous ec­o­log­i­cal prob­lems are mind bog­gling, with dire im­plica­t­ions for what’s left of that spe­cies in the north­west At­lantic Ocean if the oil reaches crit­ical man­grove habi­tat.”

A smalltooth sawfish, with a shark behind it (courtesy NOAA)

The large­tooth saw­fish, which was most com­mon in the north­western Gulf of Mex­i­co, has not been en­coun­tered in dec­ades. Its close rel­a­tive, the small­tooth saw­fish, was list­ed as an en­dan­gered spe­cies in 2003 and sur­vives in the U.S. only at the south­ern tip of Flor­i­da.

Con­serva­t­ion­ists had hoped con­di­tions would be­come fa­vor­a­ble for both saw­fish spe­cies even­tu­ally to stage a come­back in Gulf wa­ters, Bur­gess said. Far more com­mon to South and Cen­tral Amer­i­ca, the large­tooth saw­fish mi­grat­ed up the Cen­tral Amer­i­can coast dur­ing the sum­mer in­to the Gulf, the edge of its nat­u­ral ge­o­graph­ic range, he said.

“If im­por­tant un­der­wa­ter hab­i­tat is de­stroyed, nei­ther spe­cies will have a place to re­turn to,” he said. “They can’t come back to an un­der­wa­ter desert.”

A crea­ture of his­tor­ic and cul­tur­al in­ter­est, the saw­fish was some­times de­picted as a so-called mon­ster on post­cards from the turn of the cen­tu­ry, with sto­ries of its catch­ing rou­tinely pub­lished in news­pa­pers out­side Flor­i­da, Bur­gess said. To­day it is not un­usu­al to find the fish’s “saw” hang­ing from the walls of South Flor­i­da bars, he added.

The last time a large­tooth saw­fish was seen in U.S. wa­ters was in 1961, said Bur­gess, who is cu­ra­tor of the Na­tional Saw­fish En­coun­ter Database, a com­pen­di­um of all known his­tor­ic and cur­rent records of saw­fish in the Un­ited States. The preda­tor’s close rel­a­tive, the small­tooth saw­fish, once swam in bays, la­goons and riv­ers ex­tend­ing from New York to the Ri­o Gran­de, he added.

The saw­fish’s fear­some, long, toothy snout is uti­lized to stun fish­es and un­earth crus­taceans, shell­fish and oth­er food bur­ied in the bot­tom. It takes long­er for saw­fish to re­bound from a popula­t­ion crash than oth­er spe­cies be­cause of its rel­a­tively slow growth rate and its late on­set of sex­u­al matur­ity, Bur­gess warned. “Our recovery plan co­vers 100 years, which should give a pret­ty good in­dica­t­ion of how much trou­ble the an­i­mal is in,” he said.

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The oil spill caused by the collapse of a BP oil rig in the Gulf of Mexico threatens the existence of a critically endangered sawfish and its relative, said a University of Florida researcher. The animals are the only two marine fish in United States waters to receive such federal protection. The largetooth sawfish, a popular curio item known for its sawlike snout, was proposed as a federally endangered species on May 7, less than three weeks after massive amounts of oil started gushing into Gulf waters, said the university’s George Burgess. “The oil spill will not only have very dire effects on such highly visible creatures as seabirds and dolphins, but also threatens a multitude of bottom-dwelling organisms including the smalltooth sawfish, which already is in considerable trouble as its range diminished and its numbers dwindled,” he said. What’s left of the smalltooth sawfish population is confined to the lower peninsula of Florida, Burgess said, with the most important area ranging from Charlotte Harbor through the Ten Thousand Islands area of the Everglades into Florida Bay and the Keys. That’s where the largest portion of its nurseries is found and these are now threatened by the oil spill, he said. “As oil gets caught up in the loop current, it will be pulled down into the Gulf Stream, which goes right by Key West on its way up the U.S. East Coast,” Burgess said. “The opportunities for serious ecological problems are mind boggling, with dire implications for what’s left of that species in the northwest Atlantic Ocean if the oil reaches critical mangrove habitat.” The largetooth sawfish, which was most common in the northwestern Gulf of Mexico, has not been encountered in decades. Its close relative, the smalltooth sawfish, was listed as an endangered species in 2003 and survives in the U.S. only at the southern tip of Florida. Conservationists had hoped conditions would become favorable for both sawfish species eventually to stage a comeback in Gulf waters, Burgess said. Far more common to South and Central America, the largetooth sawfish migrated up the Central American coast during the summer into the Gulf, the edge of its natural geographic range, he said. “If important underwater habitat is destroyed, neither species will have a place to return to,” he said. “They can’t come back to an underwater desert.” A creature of historic and cultural interest, the sawfish was sometimes depicted as a so-called monster on postcards from the turn of the century, with stories of its catching routinely published in newspapers outside Florida, Burgess said. Today it is not unusual to find the fish’s “saw” hanging from the walls of South Florida bars, he added. The last time a largetooth sawfish was seen in U.S. waters was in 1961, said Burgess, who is curator of the National Sawfish Encounter Database, a compendium of all known historic and current records of sawfish in the United States. The predator’s close relative, the smalltooth sawfish, once swam in bays, lagoons and rivers extending from New York to the Rio Grande, he continued. The sawfish’s fearsome, long, toothy snout is utilized to stun fishes and unearth crustaceans, shellfish and other food buried in the bottom. It takes longer for sawfish to rebound from a population crash than other species because of its relatively slow growth rate and its late onset of sexual maturity, Burgess warned. “Our recovery plan covers 100 years, which should give a pretty good indication of how much trouble the animal is in,” he said.