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CPY Document 09/08/03 12:23 B813 225 7015 GMFMC ...- ...... ......- ........................ -.... .......... ..... science & Teohnology I Department of Oceanography knd ~basfalSciences1 ~ic-&d~d )'age 1 of-2 Just When You Thouaht it Was Safe to Go Back in the Water ... ,, .<:>-.*rm/<,r;F;1 :,:;!:??>*sd>,:.... -.L.>>j,. :, .. '..>',, ...... swimming closer to shore than ever before. ,,,-..... *,a:!hhb,,,{*,s.>z*,3~.. LSU researcher Ri~lteLvrulaulcry studies juver~ileblacktip sharks in the Richard Condrey, associate professor in LSU's Department of Gulf of Mexico ana belleves that Louisiana's coastal waters ^-- --- -* Oceanoaraahv and Coastal Sciences, and former araduate the nettian's best nursery s menhaden - a favorite food of young sharks - in the Atlantic Menhaden, also known as "pogies," are commonly processed to produce fish oil and feed, and therefore, are highly -.\TC.w~X~K*- animal me aust%shinrrbfEe types of prey fish sought-afier by C'X'Ilmercial fishermen. may be the rea$on more sharks are hunting fot food closer to shore. Scientists believe that more pounds of this herring-like fish are landed each year than any other fish in the country. And because Atlantic menhaden do not . generally reprod;ce until they are three years old, many are caught before they ever produce , .. offspring. According to Condrey, fewer than 10 percent of Atlantic menhaden reproduce before being caught. Guess What's Coming to Dinner? Condrey and Barry have spent the past three years studying juvenile blacktip sharks in the Gulf of Mexico and have discovered that Gulf menhaden, without question, are the sharks' meal of choice. By examining the stomach contents of young blacktips, the researchers found that the sharks feed primarily on this particular species, even selecting the largest menhaden so that one fish will completely fill their stomachs. This selective feeding pattern accounts for the rapid growth rates that Condrey has seen in juvenile Menhaden. whlch are thought to be overfished blacktips, in some U,S, waters. are a young blacktip shark's meal of choice. "For the sharks to thrive, there must be a sufficient number of menhaden to serve a$ prey," Condrey said. "Menhaden also serve as filter feeders because they feed on plankton, a process which cleans the water, The menhaden population must remain large enough so that the fish can fulfill their ecological roles as prey and as filter feeders." Managing Menhaden Since the fate of sharks - and, in fact, the entire ecological system - seems to depend so critically on the fate of menhaden, Condrey said it is essential for scientists to manage menhaden populations properly. 09/08/03 12:24 B813 225 7015 GMFMC ....... ,. ,.. ,, . , Scieil~e& Teclmology \ Department of Oceanography and Coastal Sciences( IXichard Condrey Page 2 of df' The harvesting of menhaden in the Atlantic Ocean is regulated by the Atlantic States Marine Fisheries Commission, but Condrey said the regulations fall far short of restoring menhaden stocks to levels that will maintain a healthy ecosystem. Menhaden fishing in the Gulf of Mexico is regulated by the Gulf Coast states and coordinated through the Gulf States Marine Fisheries Commission. However, Condrey said the commission has no real regulatory authority, and there are no quotas in place to limit the number of pounds harvested. While menhaden Cdndrey believes the commercial menhaden fiahing industry should be better regulated so that the populations are currently abundant in the Gulf of menhaden population remalns large enolrgh to mainlain Mexico, Condrey said that could easily change. a healthy ecosystem. "Fortunately, in the Gulf, it appears the fishery is operating on a far more ecologically sound basis than it is in the Atlantic. However, there is nothing in place to prevent overfishing in the future." Condrey said he would like to see regulations put in place that could prevent a decline in the Gulf menhaden population. "1 support an ecological approach to managing the harvesting of Gulf menhaden that provides for sufficient numbers of menhaden to support the fishery, the natural abundance of its own predators, and to allow it to fulfill its role as a filter feeder," Condrey said. We would like to stabilize the fishery at its current harvest levels, while implementing a five-year study to determine the ecological needs of the system. This wouldn't require any dramatic changes to the current harvest, he said. Even Sharks Can Be Victims A shortage of their favorite food may not be the only problem blacktip sharks have to face as a result of menhaden fishing. Another of Condrey's former graduate students, Janaka de Silva, discovered that a large number of blacktips are caught and killed in menhaden nets each year, threatening the recovery of a shark population that has also been hi$torically overfished. De Silva's research also showed that Louisiana's coastal waters are an important, but unrecognized, nursery ground for blackips and other shark i species. "Louisiana's coast is a prime nursery ground for sharks," Condrey said. "Under natural conditions, Louisiana's coast provides a freshwater outflow into a marine environment, which is a good situation for menhaden and other prey fish, and therefore, good for sharks." A number of sharks. llke these blacktips, are aught and killed in Condrey said he would also like to see regulations in the commercial menhaden nets each menhaden fishing industry that would protect sharks, dolphins and other year. important species that are ~ftencaught in menhaden nets. The "Jaws" Mentality During the past few years, shark attacks in the United States have brought renewed fear to beach-goers. Not since the "Jaws" era of the 1970s has the public seen or heard so much about shark attacks. Some scientists attribute the attacks to drought conditions, when lack of rain and freshwater runoff raised salinity levels of water near the shore, drawing saltwater prey and predators closer to shorelines. Others argue that it is media coverage - not shark attacks -that has increased. 09/08/03 12:25 B813 225 7015 GMFMC 004/004 -; .. - . a .. Science & Teclmology I Department of Oceanography and Coastal Sciences1 Richard Condrey But Condrey and his research team believe the real problem may simply be that sharks tend to follow their favorite food sources. With fewer menhaden available in deep water, sharks will cruise closer to shore to find their ideal feast, where they may accidentally come in contact with swimmers. Barry's research also shows that sharks tend to feed at dusk, a time when many recorded shark attacks have occurred. In particular, young sharks tend to swim close to shore, and Condrey believes that many recent shark attacks have been by young sharks. Large adult sharks tend to live offshore in deeper waters, but when females are ready to give birth, they ~lsuallycome in closer to shore in an area where there is an abundance of prey fish, Condrey said. After she gives birth, a mother shark will migrate back offshore, leaving her babies in an ideal nursery ground with lots of food and no large natural predators. "Young sharks have this tremendous evolutionary drive to feed and grow," Condrey said. 'They are expecting to find an abundance of their preferred food, and are not programmed to accept something other than that. There's an annual cycle of adult sharks from offshore bringing in a new crop of young sharks looking for food." Condrey said this natural phenomenon is only made worse by lack of prey fish like menhaden. "Sharks are efficient, deadly predators, and when we go swimming, we're going into their environment," Condrey said. "Our research shows that sharks have a desired feeding time, desired feeding area, and a desired prey. When those patterns are disrupted by overharvesting of a resource or some other human environmental modification, these sharks may be more likely to encounter humans in their search for food." Continuing their Work Other members of Condrey's research team included former graduate students Jeff Rester and Patrick Williams. Rester now works for the Gulf States Marine Fisheries Commission,and Williams works for the National Marine Fisheries Service at LSU. Barry now works for the National Marine Fisheries Service at its Pascagoula, Miss., laboratory, and de Silva works for the Florida Marine Research Institute - part of the Ftorida Fish and Wildlife Conservation Commission - in Tampa Bay. Barry's research at LSU was conducted on a Coypu Foundation grant, and de Silva's research at LSU was conducted on a National Marine Fisheries Service contract. Back lu top Written by Kristine Calongne I LSU Office of University Relations Photos by Kimberly Anglin and Craig Huch ~ugust2003 Related Links LSU's Department of Oceanography and Coastal Sciences Did you know?-LSU Facts Page 1 of 2 Trish Kennedy -Tom: The Billfish Network [[email protected]] mtember15,2003 3:53 PM & Su ject: Take Action! September 15, 2003 Building a Gillfishing Future! Billfish NeNVork NGWS In this issue . Welcome Hello again from Billfish Network News; our Bi- weekly e- w The W~rdon the zine that keeps you up to date on tournaments, Dock.. conservation news and more! It's Free! a NOAA Billfish Panel to Meet; Looks For Nominees The Billfish Network is a World Wide Web focused Take Action: Save the fish organization dedicated to the rebuilding of Billfish population around the world. We educate, inform, and with MFCN provide useful tools and technology for the conservation and recreational billfishing community. FS New Book Hiqhliqhts Problems in World NOAA Billfish Panel to Meet; Looks For Fisheries Nominees NOAA Fisheries will hold a meeting of the Atlantic Highly Migratory Species Advisory Panel on September 30, 2003, in Silver Spring, MD. The The Word on the Dock ... intent of this meeting is to consider management proposals in draft Amendment 1to the Fishery Management Plan for Atlantic Tunas, Swordfish, and Sharks.
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