wildlife and offshore drilling atlantic bluefin tuna

8/9/2019 Wildlife and Offshore Drilling Atlantic Bluefin Tuna

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AtlAntic Bluefin tunA in the Gulf

of Mexico

Te biology o the bluefn tuna is a world o superlatives.Fully mature, it is one o the biggest bony fshthe largestspecimen ever recorded topped 15 eet in length andweighed 1,500 pounds. Te species is also one o the astestfsh in the ocean; while marlin or sailfsh can out-sprintthem, bluefn tuna are capable o sustained speeds o nearly50 miles per hour. And among those who fsh, its reputationas the toughest, most dangerous and most prized o the gamefsh is unsurpassed.

Te bluefn tunas amazing power is derived rom an evenmore amazing muscular and circulatory system. In most fsh,blood owing to the muscles is the same temperature as thesurrounding water. But tuna (along with swordfsh, marlins

The bluen tuna is the sports car of the sea, from its sleek, muscular, metallic blue andsilvery white body to the hefty price it commandsa 500-pound specimen sold at aJapanese sh market for $175,000 earlier this year. Imperiled by the shing pressure thataccompanies such prices, the western Atlantic bluen now faces a new threat: the heart ofits breeding range lies in the path of the oil slick from the BP Deepwater Horizon disaster.

Wildlife and OffshOre drilling

The 2010 G o Mexo Dsaster:

Atat Bef Ta

and some sharks) have a heat exchange system thattransers warmth rom blood in the veins to arterial bloodowing into the muscles. Tis allows the muscles to operatemore eciently than most other fsh. In act, the musclecells o bluefns have a higher density o power-generatingstructures, called mitochondria, than most birds andmammals. Tis is why a tuna steak more closely resemblesbee than fsh.

Even more interesting, bluefn tuna appear to regulate theirheat exchange mechanism, allowing them to range widelythrough the Atlantic Ocean, rom the tropical waters near theequator to the rigid waters o the coast o Canada. una havebeen observed making more deep dives in warmer water, andit is unclear whether they can turn o their heat exchange inwarmer waters, or i they dive to colder waters to cool o.

ATlAnTic Bluin TunA nBT wu/MinDn picTu; il iG u.. cA


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Bluefn tuna eed mainly on small fsh that swim in largeschools: herring, menhaden, anchovy, sand lance, sprat andothers. Tese large schools are oten ound at upwelling zonesat the edge o the continental shel, where currents bring lots

o nutrients to the surace, triggering a east o plankton onwhich the small fsh eed. Te tuna generally eed by openingtheir mouths and charging at the school, though they willalso pursue individual larger fsh and squid, and even orageor crabs and other invertebrates on the ocean oor, particu-larly close to shore.

Atlantic bluefn tuna have two separate breeding areas:one in the Mediterranean Sea and one in the Gul o Mexico.Fish return to the area where they spawned, so the twopopulations do not interbreed, even though they intermingleas they orage. Spawning in the Gul o Mexico is concen-trated in a triangular area extending rom the western tip oCuba to the Florida Panhandle and coast o exas, peaking inmid- to late May. A mature emale can produce between 30million and 60 million eggs, though the vast majority o eggsand larvae are eaten or starve. Eggs hatch within one to twodays as larvae that are roughly a tenth o an inch long. Larvaeeed on plankton, migrate with currents out to the Atlanticand eed on progressively larger prey (such as small fsh,squid and crustaceans) as they grow.

Te Gul o Mexico population appears to breed at a laterage than the Mediterranean population: Females rom theMediterranean reach sexual maturity at three to fve years

o age, but Gul emales do not mature until they are aboutnine to 11 years old and seven eet long. Teir long periodto maturity, and the heavy fshing pressure they ace in theinterim, are major reasons the Gul population o bluefn

tuna is in jeopardy.Fishing pressure is the leading threat to bluefn tuna. Tey

are managed under the International Commission or theConservation o Atlantic unas, which regulates the fsherieso multiple species o tuna, marlin and swordfsh. Tisgroup has a long history o ailing to set quotas or fsh thatare clearly in decline, or setting quotas much higher thanrecommended by their own scientists, and or turning a blindeye when those quotas are exceeded. For instance, in 2007the catch quota or Atlantic bluefn was 29,500 tons; thatyear, Japan alone reported the import o 32,356 tons, and thetotal catch may have been double the legal quota.

A recent eort to impose a trade ban on bluefn tunathrough the Convention on International rade in Endan-gered Species ailed, with only 43 countries (including theUnited States) voting in avor o a ban, and 72 countriesvoting to continue fshing the species toward extinction.Barely a month ater that dismal result, bluefn tunawere hit with an even greater catastrophe: the DeepwaterHorizon disasterspewing oil into the Gul at the exacttime and place where the fsh concentrate to spawn,threatening not only the current generation, but also uturegenerations o bluefn.

With choice specimens o bluefn tuna

etching more than $300 a pound at

apanese fsh markets like this, fshing is

riving the species toward extinction.


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iMpActs of oil

From the perspective o bluefn tuna, the oil spill couldhardly have come at a worse time or place. May is their peakspawning time, and one o the two areas where most larvaeconcentrate lies directly in the path o the spill.

Eggs and LarvaeTe harmul eects o oil on fsh larvae have been docu-

mented or several species, and it is likely tuna larvae willbe similarly at risk. For example, among Baltic herring eggsexposed to oil concentrations o just 3.1 to 11.9 parts permillion, most hatched, but 70 percent to 100 percent weremalormed or died within a day o hatching. Survivorsshowed impaired heart rates and growth. Researchers oundthat eects worsened with increasing temperatures; watertemperatures in the Gul o Mexico are warmer than thehighest temperatures investigated in that study. Anotherstudy examined young Pacifc herring ollowing the 1989Exxon Valdezoil spill in Prince William Sound, Alaska.Researchers ound that oil-exposed larvae had abnormal

accumulations o uid in their hearts and abdomens, alongwith damage to liver, skeletal, brain and eye cells. Further-more, while the use o chemical dispersants to break the oilinto smaller particles may help keep it away rom sensitivecoasts and wetlands, it also keeps many more tiny dropletso oil in the water. Tis actually increases the exposure ormarine animals such as bluefn tuna larvae. Te dispersantsthemselves are also toxic.

AdultsTe adults producing the at-risk eggs are themselves in dangerrom the spill. Researchers rom Stanord University have beenusing satellite tagging to track adult bluefn tuna as they travelbetween spawning and eeding grounds. One adult taggedlast year entered the Gul on March 23 and spent much othe next two months in the area now covered in an oil slick.I that animal or others track a similar course this year, they

will almost certainly come into contact with large quantitieso oil. Fish swimming through oil slicks risk ouling o thegills, which intereres with oxygen uptake. Adequate oxygenis crucial to bluefn tuna, due to their high-powered musclestructure. Females also need more oxygen when they spawn.

Because o their gulping style o eeding, tuna are also atrisk o ingesting oil or tar balls along with prey. Ingested oilcan damage the liver or heart, and suppress egg production.Furthermore, even i they dont directly encounter the oilslick, bluefn can be harmed by long-term exposure throughthe small amounts o oil that accumulate in the atty fsh theyeat. Some bluefn tuna sampled rom sushi restaurants has

been ound to contain high levels o mercury, and oil residuescould similarly accumulate in tuna, potentially leading tohuman health eects.

Impacts of oil spills combined with climate change andother threatsOil in the water is not the only problem or bluefn tuna.Te burning o oil and other ossil uels is a leading

uc: ADApTD M k T Al. 2007

The timing and location o th

oil spill could not have been w

or Atlantic bluefn tuna. The G

one o only two areas in the w

where they breed, and May is

peak spawning time. Many la

inhabit waters polluted by theGeneral distribution of tuna larvae

Atlantic Bluen Tuna in the

Gulf of Mexico


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DEFEDERS OF WILDLIF

1130 17th Street, .W.

Washington, D.C. 20036

202.682.9400

www.deenders.org

contributor to climate change. Climate change adds anadditional burden to an already imperiled species. Forinstance, one impact o climate change is increasing seasurace temperatures. For bluefn tuna, water temperatureis an important actor in triggering spawning, which occurswhen the Gul o Mexico temperatures are between 72 and81 degrees F. Over the past 30 years, sea surace tempera-tures in the tropical Atlantic Ocean have increased by about2degrees F. Warmer waters hold less oxygen, which couldstress both juvenile and adult tuna. In addition, since thespecies ability to control its internal heat exchange mecha-

nism is not ully understood, tuna may overheat in warmerwaters. Furthermore, climate change is altering the timing,pattern and extent o nutrient upwellings, which govern thepopulation and location o the huge schools o small fshthat bluefn tuna rely on or ood.

WhAt citizens cAn Do

Dont buy bluefn tuna in restaurants and markets. Moresustainable alternatives include troll or pole-caughtalbacore, bigeye, skipjack and yellowfn tunas.

Urge your elected ocials to pass comprehensive climate

change legislation that addresses the impacts o globalwarming on wildlie and our natural resources.

WhAt policy MAkers cAn Do

Ensure that BP unds long-term restoration o bluefntuna populations in all Gul areas aected by the spill,including mitigation or the long-term damage caused totuna rom nonlethal exposure.

Block, B.A., S.L.H. eo1, A. Walli, A. Boustany, M.J.W. Stokesbury, C.JFarwell, K.C. Weng, H. Dewar & .D. Williams. 2005. Electronic tagginand population structure o Atlantic bluefn tuna. Nature434:1121-1127

Burros, M. 2008. High mercury levels are ound in tuna sushi.e New York Times, January 23. http://www.nytimes.com/2008/01/23/dining/23sushi.html?_r=1&ref=nyregion

Convention on International rade in Endangered Species (CIES).Bluefn una Appendix I Listing Petition. http://www.cites.org/commocop/15/raw_props/E-15%20Prop-MC%20T%20thynnus.pdf

Linden, O. 1978. Biological eects o oil on early development o theBaltic herring Clupea harengus membras. Marine Biology45 273-283.

Marty, G.D., J. E. Hose, M. D. McGurk, E. D. Brown, and D. E. Hinto1997. Histopathology and cytogenetic evaluation o Pacifc herring larvaexposed to petroleum hydrocarbons in the laboratory or in Prince WilliaSound, Alaska, ater the Exxon Valdez oil spill. Canadian Journal of Fisheand Aquatic Science54(8): 1846-1857.

McIntosh, S., . King, D. Wu and P.V. Hodson. 2010. oxicity o disperweathered crude oil to early lie stages o Atlantic Herring (Clupea harengEnvironmental Toxicology and Chemistry29(5):1160-1167.

OAA. 2010. Spill rajectory Forecast, 17 May. http://response.restoration.noaa.gov/book_shelf/2009_TMF24-2010-05-17-2100.pdf

Rooker, JR, Alvarado Bremer, JR, Block, BA, Dewar, H, De Metrio, G,Corriero, A, Kraus, R, Prince, ED, Rodriguez-Marin, E, Secor, DH(2007) Lie History and Stock Structure o Atlantic bluefn tuna (unnuthynnus). Reviews in Fisheries Science15: 265-310. Available at http://tagagiant.org/media/Rookeretal%20RFS2007.pdf.

Safna, Carl. 1997. Song or the Blue Ocean. Henry Holt & Company,ew York.

Schleistein, Mark. 2010. Bluefn una Particularly Vulnerable to Gul OSpill. New Orleans Times-Picayune, May 13. http://www.nola.com/newsgulf-oil-spill/index.ssf/2010/05/bluen_tuna_particularly_vuln.htm

REFERECES

For the latest information on the oil spill, visit www.deendersblog.org

Impose greater saety and environmental standardsand develop comprehensive spill response plans onexisting oshore drilling operations.

Prevent expanded drilling operations o the coast tolimit uture spill risks.

Enact comprehensive energy and climate changepolicies to transition away rom harmul oil andossil uels.

courTesyu.s.

nAvy

l poses a serious threat to tuna in

very lie stage. It can kill or cause organ

amage, malormations or impaired

owth in young fsh; adults swimming

rough and ingesting oil may have

fculty taking in enough oxygen or

ustain liver and heart damage.

wildlife and offshore drilling atlantic bluefin tuna

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