NORTHWEST PASSAGE OPENS FOR BOWHEAD WHALES

Bowhead whale. Via.

  
A new paper in Biology Letters reports on two satellite-tagged bowhead whales from different oceans meeting in the ice-free waters of the Northwest Passage in September 2010. 
  
One whale was from West Greenland. The other from Alaska. Their paths crossed in the Parry Channel in the Canadian Arctic Archipelago (maps, below). 
  
From the paper:
  

It is not known what attracted the whales to this area, given the region has relatively low marine production in autumn compared with other known bowhead whale feeding areas.

   

Bowhead whale bones on ceremonial ground, Point Hope, Alaska. Credit: rnoblin via Flickr.

This was not the first times whales from different waters have met in an ice-free Northwest Passage. From the paper:
  

During the commercial whaling period (i.e. pre-1900), several harpoon heads of Atlantic origin were discovered in bowhead whales harvested in the Chukchi Sea/western Arctic, but this information was largely dismissed as anecdotal by scientists. 

  
Further evidence appears in the genetic record:
  

Recent genetic studies compared DNA of whales from Foxe Basin, Canada to whales from Alaska and suggest genetic mixing, although results are based on a small sample size from a highly segregated population. The lack of genetic differentiation between whales in the Pacific and the Atlantic, acknowledging that samples are taken several thousand years apart, suggests that some exchange of individuals occurred between whales in Svalbard and Alaska. 

  

Credit: Mads Peter Heide-Jørgensen, et al. Biol Lett. DOI:100.1098/rsbl.2011.0731. 

The maps show the individual tracks of the two whales from late spring through early autumn. The inset map shows where they overlapped. From the paper:
  

The Northwest Passage with tracks of four bowhead whales and extent of sea ice with greater than 50% concentration (white fields). (a) Track of a whale tagged on 4 May 2002 in West Greenland and ice extent on 20 September 2002. (b) Track of a whale tagged in Alaska on 12 May 2006 and sea ice extent on 8 August 2006. (c) Track of a whale tagged on 24 May 2010 in Alaska, one tagged on 15 April 2010 in West Greenland, and sea ice extent on 14 September 2010. The insert shows the area where whales occurred together in 2010. The whale from Alaska was present in Viscount Melville Sound between 19 August and 18 September while the whale from Greenland was present from 11 to 28 September.

  

1980: Sea ice coverage 1 Nov-31 Jan. Credit: NASA Earth Observatory.

2012: Sea ice coverage 1 Nov-31 Jan. Red star marks approximately where the two whales met in 2010. Credit: NASA Earth Observatory.

These latest images posted by NASA's Earth Observatory give you a sense of how the passage has opened up in the last three decades for whales... and presumably for others too. I marked (red star) approximately where the two whales met in 2010.
  
The authors conclude:
  

Given recent rates of sea ice loss, climate change may eliminate geographical divisions between stocks of bowhead whales and open new areas that have not been inhabited by bowhead whales for millennia (e.g. North of Greenland and north of the Canadian Archipelago).

The documented movements of bowhead whales in the Northwest Passage are perhaps an early sign that other marine organisms have begun exchanges between the Pacific and the Atlantic Oceans across the Arctic. Some of these exchanges may be harder to detect than bowhead whales, but the ecological impacts could be more significant should the ice-free Arctic become a dispersal corridor between the two oceans.

Foxe Basin Bowhead Whales from Stephen Ambruzs on Vimeo.

The open-access ♥ paper:
  

• Mads Peter Heide-Jørgensen, Kristin L. Laidre, Lori T. Quakenbush, and John J. Citta. The Northwest Passage opens for bowhead whales. Biol Lett. DOI:10.1098/rsbl.2011.0731.

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WHALE FALL

Whale Fall (after life of a whale) from Sharon Shattuck on Vimeo.

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KILLER WHALES V. SALMON

Credit: Robert Pittman, NOAA.

What happens when we 'manage' two species in the wild with different—and conflicting—objectives? 

And what happens when one eats the other—and so do we?

That's the question raised in an interesting new paper in PLoS ONE. The authors investigated how many endangered chinook salmon are needed by endangered killer whales to recover their numbers in the northeastern Pacific.

Salish Sea, comprising the Strait of Georgia, Strait of Juan de Fuca, and Puget Sound, surrounding Vancouver Island and Washington state. Credit: SeaWiFS Project,NASA/Goddard Space Flight Center, and ORBIMAGE.

The question gets even more intriguing when you have two countries—Canada and the US—managing the fate of the two species that blithely cross international boundaries as if, you know, they weren't there.

The killer whales in the middle of the conflicted question are known as the southern resident killer whales (SRKW), who summer in the Salish Sea. They eat only fish, and are so dependent on chinook salmon that when they can't get them more adult whales die and fewer calves are born. 

• Current population of southern resident killer whales: 87 individuals
• Current chinook salmon stock: 36% of historical run in Canada, 8% in US

Chinook salmon. Credit: Josh Larios via Wikimedia Commons.

The stated objective of US management is to grow the dwindling killer whale population by 2.3% per year over 28 years. 

The authors assessed what the minimum basic caloric requirements were likely to be to make that come true—based on food requirements of captive killer whales, and body lengths of wild whales.

Estimated prey requirements of wild killer whales, based on two plausible values for calorie content of a typical, 4-year-old Chinook salmon. Credit: Rob Williems, et al. PLoS ONE. DOI:10.1371/journal.pone.0026738.

What they found suggests that the chinook salmon can't support both a growing killer whale population and human fisheries at current levels.

What's a fish-eating primate to do? The authors' suggest:

When one protected species relies almost exclusively on another protected species, it can be difficult to develop management frameworks that meet the needs of both species. This can lead to a perception that the needs of the more charismatic species will unfairly trump those of the prey species. In our experience, genuine conservation conflicts often result in management inaction in the absence of a framework in which to assess likely impacts... It is faster to reduce takes of salmon than to increase salmon production, and it is faster to increase salmon production than promote population growth in killer whales. The efficacy of salmon habitat restoration actions can often be measured within a decade, whereas similar measurements will take decades in studies of long-lived species like killer whales.

In other words, maybe we should let the whales get the fish for a while.

There's a lot more interesting stuff going on in this forward-looking paper and luckily it's open access. So you can freely read deeper.

The paper:

• Williams R, Krkošek M, Ashe E, Branch TA, Clark S, et al. 2011Competing Conservation Objectives for Predators and Prey: Estimating Killer Whale Prey Requirements for Chinook Salmon.PLoS ONE 6(11):e26738. DOI:10.1371/journal.pone.0026738

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TWICE AS MANY DOLPHINS, WHALES STILL DYING IN GULF

Stranded spinner dolphin. Credit: qnr via Flickr.

  

The latest NOAA report on unusual strandings of whales and dolphins in the northern Gulf of Mexico finds they're still dying at twice the normal rate 18 months after BP's Deepwater Horizon disaster.

Map of strandings in relation to Deepwater Horizon well. Click for larger version. Credit: NOAA.

  

As you can see in the map above, the most heavily oiled shoreline still corresponds with the most dead whales and dolphins.

Bottlenose dolphins are shown as circles and other species as squares. Premature, stillborn, or neonatal bottlenose dolphins (with actual or estimated lengths of less than 115 cm/45 inches) are shown as a circle with a black dot inside. 

Pink points mark the most recent week of data. Green points mark are all other cases since 1 January 2011.

 

All stranded cetaceans (dolphins and whales) from Franklin County, FL to the Texas/ Louisiana border. Credit: NOAA.

Here you can see how the numbers of strandings have not yet stabilized or even begun to decline. In some cases they're still growing. 

The magenta-colored bars mark strandings per month in the year 2010. The ivory-colored bars mark strandings per month so far this year.

Credit: NOAA.

This graph shows stranded premature, stillborn, or neonatal bottlenose dolphins.

In my Mother Jones article The BP Cover-Up last year, I wrote about the kind of long-term problems the Gulf might face not just from oil but from extreme quantities of oil in very deep water, as well as from chemical dispersant, including dispersant injected into very deep water.

Sadly, it seems that cetaceans—past, present, and future—may be bearing some of those burdens.

Beached sperm whale. Credit: Rachel Denny Clow, Corpus Christi Caller-Times/AP.

  
You might be interested in these other posts describing other scientific findings in the wake of last year's Gulf catastrophe:

• Canadian Seabirds Walloped by BP's Oil
• Gulf Oil Hammers Fish
• Deepwater Horizon's Uncounted Victims
• The BP Cover-Up

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WATER WINGS

Flying gurnard. Credit: cralize via Wikimedia Commons. / Spotted eagle ray. Credit: john norton via Wikimedia Commons. / Green sea turtle. Credit: Mila Zinkova via Wikimedia Commons. / Weedy sea dragon. Credit: Richard Ling (Rling) via Wikimedia Commons. / Lionfish. Credit: Jens Petersen via Wikimedia Commons. / Cuttlefish. Via. / Icefish. Credit: Uwe Kils via Wikimedia Commons. / Humpback whales. Via. / Hammerhead shark. Via. / Manatee. Via. / Sea lions. Credit: NOAA. / Manta ray. Via. / Flying fish. Via.

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WHERE WHALES WANDER

Sperm whales. Credit: NOAA.

    
A new paper in MEPS (Marine Ecology Progress Series) describes for the first time the communities—villages, in a sense—of whales and dolphins living offshore in the northwest Atlantic and the Gulf of Mexico.

This is a mind-bogglingly difficult thing to assess, as you might imagine, in a world beyond our sight and wildly three-dimensional... where far-from-still waters run hundreds if not thousands of meters/feet deep. As the authors dryly observe:

Data collection on the distribution and abundance of marine mammals is costly, time consuming and complicated by logistical difficulties.

Humpback whales. Credit: NOAA.

   
Nevertheless, this team of 15 researchers—themselves clustered along the East Coast, with one outlier in the Bahamas—availed themselves of an archive of datasets on cetacean distribution and abundance. These covered the waters from Nova Scotia to the Gulf of Mexico.

Specifically, the team used OBIS-SEAMAP sightings, collected over many years from vessels both at sea and in the air during the summer months of June, July, and August.

Marine mammal sightings 1990-2010. Credit: OBIS-SEAMAP.

 
Duke University's OBIS-SEAMAP (Ocean Biogeographic Information System—Spatial Ecological Analysis of Megavertebrate Populations) is a seriously cool tool. Above is a map I generated for marine mammal sights between 1990-2010. You can play around with the datasets—which include seabirds and sea turtles too—and generate your own maps.

The authors were looking for signs of community structure at really large spatial scales, on the order of thousands of kilometers/miles. And they found it.

The regions North of Hatteras (NOH) and South of Hatteras (SOH). (a) Overview. (b) Sampling hexagons (NOH: light grey; SOH: dark grey). Sightings are depicted at the taxonomic guild level with different colors and symbols. Depth contours (200, 500, 1000, 2000 m) in light grey. GOM: Gulf of Mexico. Credit: R. S. Schick, et al. MEPS. DOI:10.3354/meps09183.

  
This glorious map shows the distribution of 16 species or species clusters (e.g., beaked whales, baleen whales) in waters North of Cape Hatteras and south of Cape Hatteras. Depth contours are included—though you can't really see them on the small map I posted here. For a higher resolution image, download the PDF of the paper.

As you can see, things get seriously busy up there in the colder, productive waters north of Cape Hatteras, where harbor porpoises and baleen whales rule, where bottlenose dolphins own the inshore realm, and where toothed whales work the drop-offs to the deep. These waters also had the biggest datasets.

And take a look at the map above and the fascinating zigzag distribution of Atlantic spotted dolphins (blue dots)—running back and forth across the Gulf Stream to the south of Cape Hatteras. Having worked many years filming those guys in the Bahamas, I find it really exciting now to see a bigger picture.

The Gulf of Mexico (GOM). (a) Overview. (b) Sampling hexagons in light grey. Sightings are depicted at the taxonomic guild level with different colors and symbols. Depth contours (200, 500, 1000, 2000 m) in light grey. Credit: R. S. Schick, et al. MEPS. DOI:10.3354/meps09183.

  
Turns out the spotted dolphins living in the Gulf of Mexico are distributed much like those along the Gulf Stream—zigzagging inshore and offshore from Mobile Bay to the Florida Keys (above).

You can also see how many species—Risso's dolphins, sperm whales, common dolphins, bottlenose dolphins, and killer whales—congregate in the waters enriched by the Mississippi River. Also the disaster site of last year's Deepwater Horizon blowout.

Sea surface temperatures on 4 Aug 2011 at 0756 GMT. Credit: NOAA, Rutgers University Coastal Ocean Observation Lab

The researchers connected the position of each sighting with each of seven environmental layers:

1. Sea surface temperature (SST)
   
2. Chlorophyll a concentration [a mark of ocean productivity]
3. Bottom depth
4. Distance to continental shelf (defined by the 200 m isobath)
5. Distance to shore
6. Probability of an SST front [a place where water masses of different water temperatures meet]
7. Depth of the mixed layer (MLD)

Killer whales. Credit: NOAA.

 
The overall findings for the three biogeographic regions are interesting:

North of Hatteras, we found 2 main groups split along a temperature and chlorophyll [indicating phytoplankton abundance] gradient, with most piscivores [fish-eaters] being found in cooler, more productive waters of the continental shelf, and most teuthivores [squid-eaters] being found farther offshore in warmer, less productive waters at the shelf break (200 m isobath). South of Hatteras, we found 3 groups, with the largest group being in warmer, lower chlorophyll waters that are closest to shore. In the Gulf of Mexico, we found 7 groups arrayed along a bottom depth gradient.

The Domesday Book on display at Britain's National Archives.

  
To my mind, this paper is the ocean equivalent of Britain's Domesday Book, the great survey concluded in the year 1086 of much of England and parts of Wales. That effort provided a snapshot of the geography of human habitation and ownership at the time. This paper delivers something of the same for the shifting villages of ocean nomads—travellers in a fluidly moving realm.

The paper:

• ♥ Schick RS, Halpin PN, Read AJ, Urban DL and others (2011) Community structure in pelagic marine mammals at large spatial scales. Mar Ecol Prog Ser 434:165-181. DOI: 10.3354/meps0918.

♥ Open-access paper.

Common dolphins. Credit: NOAA.

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RIGHT WHALES DECODED

Southern right whale. Credit: © Brian J. Skerry / National Geographic Stock. Via the World Wildlife Fund.

An interesting new paper in MEPS (Marine Ecology Progress Series) on the southern right whales of New Zealand and Australia.

Background: All right whales, north and south, were taxed hard and early by human whalers—the "right" whales to hunt because their high blubber content made them likely to float after death and because they frequented near-shore waters.

That made them easy to get to even in the days of rowing.

A painting, artist unknown, showing the hunting of right whales. La Baleine. The Whale, circa 1840. Credit: Wikimedia Commons.

Some 150,000 Southern Hemisphere right whales (Eubalaena australis) were killed by 19th-century whalers and by illegal 20th-century Soviet whalers—driving the species to the brink of extinction.

Around Australia and New Zealand, hunting peaked in the 1830s-1840s, after which the species was commercially extinct.

Geographic range of the southern right whale. Via the Red List.

The latest IUCN estimate of southern right whales dates back to 1997 when they calculated a population of 7,500 individuals. 

At that time, several breeding populations (in Argentina/Brazil, South Africa, and Australia) showed evidence of strong recovery, with a doubling time of 10-12 years.

Which means there might be a fair few more than 7,500 whales today.

Southern right whale with calf. Credit: John Atkinson. Via Marine Science Today.

According to the authors of the MEPS paper, no right whales were seen in the waters around mainland New Zealand for 35 years between 1928 and 1963. A few slowly returned. Yet as recently as 2005 less than 12 sexually mature females were found there.

But another group, known as the New Zealand subantarctic group, has a more robust population estimated at about 936 whales today. Forebears of this group were likely present in some small numbers even in the bleakest killing years.

Credit: E. Carroll, et al, via MEPS.

The authors of the MEPS paper wondered about the levels of relatedness between those two whale stocks in New Zealand, as well as among whales in Australia.

They used mitochondrial DNA and microsatellite genotypes to identify 707 individual whales and test them for genetic differentiation. You can see the breakdown of that analysis in the graphic above.

Their data, combined with historical evidence, led the researchers to hypothesize that individuals from the NZ subantarctic are slowly recolonizing mainland New Zealand waters, where a calving ground was obliterated in the 19th century.

Southern right whale. Via.

The genetic evidence also suggests that the whales of southeast Australian are a remnant stock—different from the whales of southwest Australia:

At the onset of whaling, southern right whales, in particular cows with calves, were found across the southern coast of Australia during the austral winter (IWC 1986). There was no real discontinuity in distribution or catch records to suggest subdivision of calving grounds in this region (IWC 1986). Based on the timing of catches at shore whaling stations during the 19th century, Dawbin (1986) proposed that southern right whales undertook 2 distinct patterns of migration along the southern coast of Australia during the austral winter. The southern right whales that migrated north along the east coast of Tasmania [the small island off the southeast tip of Australia, as seen in the graphic above] moved in a northeasterly direction up the coast of Victoria and New South Wales, while those that migrated north along the west coast of Tasmania moved from east to west along the southern coast of South and Western Australia. The latter pattern is still extant, based on the movement of photo-identified southern right whales and has been termed the 'counter-clockwise' migratory pattern (Kemper et al. 1997, Burnell 2001).

The Southern Ocean. Credit: Connormah via Wikimedia Commons.

They also found evidence that New Zealand and Australian right whales mingle in higher-latitude summer feeding grounds each austral spring—making the health of those cold Southern Ocean waters as important a component of recovery as the whales' breeding efforts.

And what epic efforts they are. Imagine a 12-foot-long penis—known colloquially as a sea snake—plus a tons' worth of testes per male. Mating becomes a sport of endurance. And sperm competition.

But you don't have to imagine it. As usual, just for us, David Attenborough respects the privacy of none.

The paper:

• Carroll, E., Patenaude, N., Alexander, A., Steel, D., Harcourt, R., Childerhouse, S., Smith, S., Bannister, J., Constantine, R., & Baker, C. (2011). Population structure and individual movement of southern right whales around New Zealand and Australia Marine Ecology Progress Series DOI: 10.3354/meps09145

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THE PELAGIC ZONE

PIELAGO from Rafa Herrero Massieu on Vimeo.

Here's some of the most beautiful footage of one of my favorite worlds—the bottomless blue waters far offshore known as the pelagic zone. Life here shines.

Whether you've had the good fortune to visit this realm or not, you're in for a treat with this short film by Rafa Herrero Massieu, shot in the waters around the Canary Islands. 

A few highlights to look out for, with timecodes:

• Rare underwater footage of a beaked whale (not sure which species): 01:10
• Common dolphins showing their gorgeous colors: 01:16
• An Atlantic spotted dolphin emitting signature whistles: 01:26
• Bryde's whale (I think, or else a Sei whale): 03:23

(Loggerhead turtle. Credit: ukanda via Wikimedia Commons.)

Because big life is relatively sparse in the pelagic zone, encounters between individuals tend to generate a lot of curiosity. 

You can see how all these species investigate the novelty of a person in their world—particularly the pilot whales at 03:00 and the triggerfish at 03:21.

For more of Rafa Herrero Massieu's films, visit his blog: NacidasDelMar (Born of the Sea), or his Vimeo page.

(Strata of the pelagic zone. Measurements in meters. From here.)

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DEEPWATER HORIZON'S UNCOUNTED VICTIMS

(Killer whales. Photo by Pittman, courtesy NOAA, via Wikimedia Commons.)

A new paper in Conservation Letters calculates that the numbers of whales and dolphins killed in BP's Deepwater Horizon disaster could be 50 times higher than the number of carcasses found. 

The authors—a high-powered list of renowned cetacean researchers from Canada, the US, Australia, and Scotland (including Scott Krause, who I filmed years ago for a documentary about North Atlantic right whales)—write of a general misperception of the Deepwater Horizon impact:

Many media reports have suggested that the spill caused only modest environmental impacts, in part because of a low number of observed wildlife mortalities, especially marine mammals.

(Atlantic spotted dolphins. Photo by Bmatulis, via Wikimedia Commons.)

Compared to the 1989 Exxon Valdez, with its iconic oiled otters and high body counts, the Deepwater Horizon seems, well, not so bad.

The authors point out that "only" 101 dead cetaceans (whales, dolphins, and porpoises) were found in the Northern Gulf of Mexico as of 7 November 2010. The number's misleading though.

The issue arises when policymakers, legislators, or biologists treat these carcass-recovery counts as though they were complete counts or parameters estimated from some representative sample, when in fact, they are opportunistic observations. Our study suggests that these opportunistic observations should be taken to estimate only the bare minimum number of human-caused mortalities.

(Humpback whale. Photo by Whit Welles Wwelles14, via Wikimedia Commons.)

So how many more whales, dolphins, and porpoises actually died? That problem is tough to figure to begin with and is compounded by a dearth of data in the Gulf—a fact that will work greatly in BP's favor when the time comes to levy fines.

The Gulf of Mexico is a semi-enclosed subtropical sea that forms essentially one ecosystem with many demographically independent cetacean populations. Some of these cetacean populations, such as killer whales (Orcinus orca), false killer whales (Pseudorca crassidens), melonheaded whales (Peponocephala electra), and several beaked whale species, appear to be quite small, are poorly studied, or are found in the pelagic realm where they could have been exposed to oil and yet never strand. Small, genetically isolated populations of bottlenose dolphins (Tursiops truncatus) could have experienced substantial losses either inshore or offshore.

(Mother and calf bottlenose dolphins. Photo by M. Herko, courtesy NOAA, via Wikimedia Commons.) 

Two methods of extrapolation could shed light on how many cetaceans BP's disaster killed:

1. Compare abundance before the disaster to abundance after—but since we don't know the population size of whale and dolphins species in the Gulf before hand we're unlikely to notice anything short of "the most catastrophic decline" and maybe not even that.
2. Count the number of carcasses recovered—knowing that many will evade our count, having sunk, decayed, been scavenged, or drifted away. So adjust the counts upward to estimate total mortality. This approach is used to estimate bird deaths at power lines, where, in at least one instance, we now know that bird body counts underestimate total actual deaths by a whopping 32 percent.
   

The authors worked the two methods as best they could and added something more.

Given the magnitude of the spill and complexity of the response, quantifying the ecological impacts will take a long time. To contribute to this effort, we examined historical data from the Northern Gulf of Mexico to evaluate whether cetacean carcass counts in this region have previously been reliable indicators of mortality, and may therefore accurately represent deaths caused by the Deepwater Horizon/BP event.

(Sperm whale. Photo courtesy NOAA, via Wikimedia Commons.) 

Their methods and analysis suggest that an average of 4,474 cetaceans died in the northern Gulf every year between 2003 and 2007 from all causes, human and natural. Yet since an average of only 17 bodies were found in those years, the body count represented only ~0.4 percent of total deaths.
 

Consider, for example, one sperm whale being detected as a carcass, and a necropsy identified oiling as a contributing factor in the whale’s death. If the carcass-detection rate for sperm whales is 3.4%, then it is plausible that 29 sperm whale deaths represents the best estimate of total mortality, given no additional information. If, for example, 101 cetacean carcasses were recovered overall, and all deaths were attributed to oiling, the average-recovery rate (2%) would translate to 5,050 carcasses, given the 101 carcasses detected.

Those are chilling numbers. Period. But also in light of the relatively tiny populations of cetaceans in the Gulf. Especially since most if not all cetaceans are highly social, and since oil and chemical dispersants likely injured, sickened, or killed entire clusters, schools, pods, matrilines, or groups at the same time—and may still be doing so.

The authors describe the near-lethal affect of the Exxon Valdez disaster on one well-known and well-studied pod of killer whales in Alaska.

In the first year after the 1989 Exxon Valdez spill, the AT1 group of "transient" killer whales experienced a 41% loss; there has been no reproduction since the spill. Although the cause of the apparent sterility is unknown, the lesson serves as an important reminder that immediate death is not the only factor that can lead to long-term loss of population viability.

(Pilot whale mother and calf. Photo by Clark Anderson via Wikimedia Commons.)

The paper:

Rob Williams, Shane Gero, Lars Bejder, John Calambokidis, Scott D. Kraus, David Lusseau, Andrew J. Read, & Jooke Robbins (2011). Underestimating the damage: interpreting cetacean carcass recoveries in the context of the Deepwater Horizon/BP incident Conservation Letters : 10.1111/j.1755-263X.2011.00168.x

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