Home's

Hector's dolphin. Credit: James Shook via Wikimedia Commons.

This species is considered to be Endangered due to an ongoing and projected decline of greater than 50% over 3 generations (approx. 39 years)... Hector’s dolphin has the most limited range of any marine cetacean other than the vaquita (Phocoena sinus)... The main cause of population decline is ongoing bycatch in [gillnet and trawl] fisheries.

  
Concerned for the future of this rare species (population: 7,270 individuals), New Zealand in 1988 established the Banks Peninsula Marine Mammal Sanctuary in 1,170-square-kilometers (451-square-miles) of waters off the South Island. 

Banks Peninsula, South Island, New Zealand. Credit: NASA Astronaut Photo ISS013-E-67242.

The research, ongoing since 1986, involved identifying 462 individual Hector's dolphins through photographs and then analyzing the photographic re-sightings using a Bayesian mark-recapture technique. The team applied a population model to assess the impact of the MPA on the dolphins.

Their results show that since the designation of the sanctuary, the Hector's dolphins' survival rate has increased by 5.4 percent: 

• From a decline of ~6 percent per year
• Now slowed to a rate of decline of ~1 percent per year

As good as that sounds, the researchers were surprised survival rates hadn't increased further, since they expected the establishment of the MPA to solve the problem entirely.
    

Hector's dolphin. Credit: David Searle via Flickr.

Instead they discovered the dolphins don't spend the whole year in the sanctuary. Co-author Liz Slooten tells me:

Their distribution with respect to depth and distance offshore changes. In winter they are almost evenly distributed with respect to depth and distance offshore. In summer they are strongly concentrated close to shore. This means that in summer about 80% of the population is inside the sanctuary and protected. In winter this drops to only about 40%. Too many dolphins are still being caught in fishing nets to allow the population to stabilise, let alone recover from the massive decline they've suffered over the last three decades.

"The MPA hasn't quite yet 'saved' the dolphins," says Slooten, "but it's been a major step in the right direction. The take home message is that size matters. Marine Protected Areas work, but they have to be large enough in order to be effective."

• Andrew M Gormley, Elisabeth Slooten, Steve Dawson, Richard J Barker, Will Rayment, Sam du Fresne and Stefan Brager (2012). First evidence that Marine Protected Areas can work for marine mammals. Jour. App. Ecol. DOI: 10.1111/j.1365-2664.2012.02121.x

Stranded spinner dolphin. Credit: qnr via Flickr.

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

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

Credit: NOAA.

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

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

• 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

This memoir covers three phases of my more than thirty years spent among dolphins and other sea creatures: my initial, exhilarating encounter with friendly dolphins; my subsequent discovery that these creatures are mortally threatened by both slaughter and the chemical contamination of our oceans; and, finally, my diagnosis with a form of blood cancer that has clear links to the same chemical toxins that are causing disastrous consequences among dolphins.

Dolphins raced at me from all directions, their eyes wide and bloodshot with excitement. The sea was a cacophony of breaking waves, my own gasping, yells, outboard motors, and the creaky-door buzzing of dolphin sonar. Whenever I surfaced, I tried to get some idea of how the filming was going, but no one was even remotely coherent. Words tumbled out of ecstatic faces...

I made a surface dive and swam down among a mixed group of juvenile and adult dolphins, blending into their formations, banking and turning in mid-water. It seemed I had no need to breathe, that I’d assumed properties of a dolphin just by being among them. When my air did run out, I clawed my way back to the surface and gasped for breath, often to find a trio of dolphins accompanying me.

Again and again, especially in early morning hours when I couldn’t sleep, my thoughts returned to the brutal images of dolphins piled on the beaches of Iki... I placed an aerial photograph of the dead dolphins littering the beach at Iki on my desk. Next to that photograph, stood a framed print of two dolphins, looking at me as we swam side by side in the turquoise waters of the little Bahama Bank.  

In the course of my travels to Japan, I’d come to realize that... a major part of the incentive to local fishermen to pursue and kill dolphins is cash put on the table by international dolphin traffickers who come to Taiji to pick out "show-quality" dolphins. They pay enormous amounts, as much as $150,000 for a dolphin trained in Taiji. The service includes trainers who will accompany the locally trained dolphin to its final destination in one of the many dolphinaria in Japan, as well as to China, Korea, French Polynesia, Turkey and Egypt. For dolphins, this must be the equivalent of an alien abduction. The captive dolphins eventually end up in a cement tank performing for fish in aquarium shows and "swim-with-dolphins" programs around the world.

When the show hit the air, the results were explosive. The emotional impact of the footage was amplified by a short PSA hosted by George C. Scott that included a 900 number, produced for the show by Stan Minasian of the Marine Mammal Fund. The result was a pile of six thousand telegrams hitting the desk of the chairman of Starkist tuna demanding an end to catching tuna by setting nets on dolphins. Within weeks, Starkist announced that it would no longer accept tuna caught on dolphin. The dolphin-safe label was born and is today overseen by Earth Island Institute and the Marine Mammal Fund. My film synergized with years of hard work by several organizations and was a major conservation victory.

In follow-up conversations with [PBS], we mapped out the general shape of the film that would be an episodic journey through my career of making films about dolphins. It would combine archival footage shot over a period of several decades with newly shot footage that would fill in gaps in the story and bring it up to date... I hadn’t looked at a lot of that old film for years, and as I started to screen bits and pieces, memories flooded back with a combination of exhilaration, nostalgia, and not a few thoughts of how young I looked. The reaction was, no doubt, intensified by my new-found sense of mortality. 

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.

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.