Sono­gram that shark

Sci­en­tists de­velop a dar­ing preg­nancy exam... for sharks.

The Star Malaysia - Star2 - - SCIENCE - By JENNY STALE­TOVICH

FOR years, warm shal­low wa­ters in a cor­ner of the Ba­hamas have drawn an as­ton­ish­ing num­ber of large tiger sharks, mys­ti­fy­ing sci­en­tists study­ing their epic mi­gra­tion pat­terns.

Now a team of sci­en­tists, in­clud­ing Univer­sity of Mi­ami shark ex­pert Neil Ham­mer­schlag, may have their an­swer thanks in part to a new study tech­nique re­ly­ing on ul­tra­sound.

As in the kind to check tiger shark baby bumps.

Talk about need­ing a good bed­side man­ner.

Ham­mer­schlag first be­gan div­ing the site near West End known as Tiger Beach in 2003 and no­ticed some­thing sur­pris­ing: nearly all the sharks were fe­male.

Hav­ing a con­stant smor­gas­bord of dive tour oper­a­tors chum­ming wa­ters could be the rea­son for the num­bers, he said. But that didn’t ex­plain the ab­sence of males. So maybe, he rea­soned, it had some­thing to do with re­pro­duc­tion.

While sharks draw a lot of at­ten­tion – who doesn’t have Shark Week marked on their cal­en­dars? – lit­tle is ac­tu­ally known about how they live and love.

Only one species, nurse sharks, has been doc­u­mented mi­grat­ing to the Dry Tor­tu­gas in early sum­mer to mate, ac­cord­ing to the team’s study, pub­lished re­cently in Aquatic Bi­ol­ogy.

Lemon sharks will travel to Bi­mini to give birth while black­tip reef sharks travel to French Poly­ne­sia. Part of the prob­lem comes from doc­u­ment­ing re­pro­duc­tion. Un­til now, re­pro­duc­tion stud­ies usu­ally re­quired killing and cutting open sharks, some­thing re­searchers don’t rel­ish.

So Ham­mer­schlag and co- au­thor James Su­likowsky, of the Univer­sity of New Eng­land, got to think­ing about over- the- counter preg­nancy tests and the way hu­mans con­firm preg­nan­cies.

“When you want to tell if they’re preg­nant, you don’t have to kill them, thank good­ness,” he said. “We wanted to com­bine the over­the- counter and a doc­tor’s visit.”

Just at sea. With a man- eat­ing 4m shark than can weigh as much as 630kg.

Por­ta­ble, wa­ter­proof sono­grams de­vel­oped for an­i­mal hus­bandry made the job eas­ier. The sono­grams are light­weight, easy to ma­noeu­vre and come with gog­gles, rather than a screen, to view images. What still re­mained dif­fi­cult was get­ting the sharks to keep still. Or not take a chunk out of the doc­tor, un­der­stand­able given a shark’s 16- month ges­ta­tion pe­riod.

This is where be­ing an ex­pert shark hunter comes in handy.

First the team baited lines at­tached to a se­cure float­ing drum, which they checked ev­ery hour. Once hooked, the team reeled in the sharks, us­ing their 66- foot re­search boat to back down on the fish in a kind of tug- of- war that evened the play­ing field, since the sharks are big enough to pull an an­gler over­board.

Once close enough to the boat, a team mem­ber would lasso the shark’s tail and pull it out of the wa­ter, es­sen­tially dis­abling the shark’s pro­pel­ler.

Other mem­bers then wres­tled it aboard a sub­merged plat­form and in­serted a 3- inch PVC pipe into its mouth to pump oxy­genated salt­wa­ter over the shark’s gills. In ad­di­tion to the sono­gram, re­searchers also drew blood to mea­sure hor­mone lev­els.

To­tal exam time: about 20 min­utes.

While this plan may not sound ex­actly fool­proof, re­searchers had a few things go­ing for them, Ham­mer­schlag said.

First, sharks bite when they’re stressed. So the pipe acted like a pacifier. Sec­ond, the pumped wa­ter had a higher oxy­gen con­tent, which also soothed the sharks.

“Ev­ery now and then ( a shark) kind of tenses up and wrig­gles around and you let it do what it wants,” he said.

Of the 65 sharks caught be­tween 2011 and 2014, 59 were fe­males. Of those, some were preg­nant. Ju­ve­nile fe­males, but no ba­bies, were also present. The area’s shal­low sandy bot­tom pro­vides lit­tle for for­ag­ing, but wa­ter is warm and mostly calm.

Be­cause shark cop­u­la­tion tends to be vi­o­lent – males of­ten bite to hang on dur­ing the act – the team the­o­rised that the area serves as a safe haven for moth­ers- to- be and im­ma­ture fe­males.

The warm wa­ter might also as­sist ges­ta­tion, fol­low­ing the bunin- the- oven the­ory.

The same has been seen in nurse sharks, the team re­ported. Be­cause the area lies within the pro­tected Ba­hamas Exclusive Eco­nomic Zone, the team also be­lieves the find­ings might show the value of con­ser­va­tion ef­forts for tiger sharks, which glob­ally are con­sid­ered threat­ened but have be­gun to re­bound in the At­lantic Ocean.

“A lot of shark pop­u­la­tions are de­clin­ing in the At­lantic, but it seems tiger sharks are on a re­cov­ery trend and it may be in large part be­cause of the Tiger Beach area,” Ham­mer­schlag said.

Asked if any­thing sur­prised him dur­ing the three- year study, Ham­mer­schlag said this: “It amazed me that some­times the big fe­males are not preg­nant. I’d think they were preg­nant when in fact they just ate a sea tur­tle.”

Awk­ward. – Mi­ami Her­ald/ Tri­bune News Ser­vice

When you want to tell if they’re preg­nant, you don’t have to kill them, thank good­ness. We wanted to com­bine the over- the- counter and a doc­tor’s visit. Just at sea. With a man- eat­ing 4m shark than can weigh as much as 630kg. neil ham­mer­schlag, Univer­sity of Mi­ami shark ex­pert

A fe­male shark swims in shal­low wa­ter near Lit­tle Ba­hama Bank nick­named Tiger Beach be­cause of the nu­mer­ous tiger sharks found in the area. — Photos: TnS

Univer­sity of new Eng­land re­searcher Carolyn Wheeler uses a por­ta­ble ul­tra­sound ma­chine to ex­am­ine a fe­male tiger shark.

re­searchers used ul­tra­sound in a study that found Tiger Beach near Lit­tle Ba­hama Bank acts as a safe haven for preg­nant and young fe­male tiger sharks.

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