Tuesday, November 27, 2007

On the Beeb

BBC Radio 4 ran a two-part programme on whaling. I get to chat a little in the second part, from Monday 26th.

Link is here
There is no more of this one

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Monday, November 19, 2007

A little about me....................


In 1989, I was awarded my PhD on the behaviour and ecology of bottlenose and humpback dolphins in Moreton Bay, off Brisbane, making me the first Australian to get a PhD by studying living cetaceans. By then, I'd already started on my next project, assessing the effects of the then-new whale watching industry in Hervey Bay. That work provided the primary scientific input for establishing the Hervey Bay Marine Park, the first marine park established to manage commercial whale watching.

The dolphins I studied in my Ph.D. work were affected by fisheries. Trying to understand how we humans affect marine mammals, and helping to mitigate problems that are identified through research, has been the focus of my work since then. While in Australia I worked on humpback and right whales; dugongs; snubfin, humpback and bottlenose dolphins. The work took me from islands a few miles from Papua New Guinea to the desert by the sea at the Head of the Great Australian Bight, and to the edge of the Antarctic pack ice.

But I ended up in a strange employment situation – acting as a tenured faculty member at a University, but employed on short-term teaching contracts. Something had to give. My wife won a great postdoctoral fellowship to work at the Norwegian Polar Institute in Tromsø, and a job came up for a population ecologist to work on seals at another research group in the same town – the choice was clear.

Given Norwegians' fame as marine mammal hunters, this probably seems like a strange move, but I'd worked with Aboriginal people hunting dugongs in northern Australia, so I was under the impression that the job in Norway would involve something similar – using science to work towards ensuring that hunts were sustainable. To my shock, I found myself in a research group where the main interest seemed to be providing scientific backing to the idea that marine mammals should be culled in the name of “Ecosystem-Based Fishery Management”. This site has stories of my time working in that group – so far, on a survey of harp seals, and a “lethal sampling” trip to the ice of east Greenland.

In early 2004, the Norwegian parliament instituted a new policy on managing marine mammals, giving official approval to the idea that ecosystem management is all about culling. I refused as a matter of principle to work on research that would support the policy, and so had no option other than to resign my Principal Scientist job.

We moved to the USA in mid-2004. I've discovered just how costly it is to resign over a matter of principle. Not recommended as a Good Career Move.

For a sense of my academic work, here are some (relatively) recent papers from my areas of interest. I have most of these as pdfs, so if you want one, just shoot me an email:

Marine mammals and “Ecosystem-Based Fishery Management”:

Corkeron, P. J. 2006. Opposing views of the “ecosystem approach” to fisheries management. Conservation Biology 20: 617-619.

Corkeron, P.J. 2004. Fishery Management and Culling. Science. 306:1891.

Whale watching, sustainability and what whales mean to us:

Corkeron, P.J. 2006. How shall we watch whales? pp 161-170 in D.M. Lavigne (ed). Wildlife Conservation in Pursuit of Ecological Sustainability. Proceedings of an International Forum. The International Fund for Animal Welfare, Guelph, Canada and the University of Limerick, Limerick, Ireland.

Corkeron, P.J. 2004. Whalewatching, iconography and marine conservation. Conservation Biology. 18: 847-849.

Marine mammals of tropical coasts – conservation biology:

Parra, G.J., Corkeron, P.J. and Marsh H. 2006. Population sizes, site fidelity and residence patterns of Australian snubfin and Indo-Pacific humpback dolphins: implications for conservation. Biological Conservation 129: 167-180.

Parra, G.J., Schick, R., and Corkeron, P.J. 2006. Spatial distribution and environmental correlates of Australian snubfin and Indo-Pacific humpback dolphins. Ecography 29: 1-11.

Chilvers, B.L. Corkeron, P.J. and Puotinin, M.L. 2003. The influence of trawling on the behaviour and spatial distribution of Indo-Pacific bottlenose dolphins, Tursiops aduncus, in Moreton Bay, Australia. Canadian Journal of Zoology. 81: 1947-1955.

Chilvers, B.L. and Corkeron, P.J. 2003. Abundance of Indo-Pacific bottlenose dolphins Tursiops aduncus, off Point Lookout, Australia. Marine Mammal Science. 19: 85-95

Chilvers, B.L. and Corkeron P.J. 2001. Trawling and bottlenose dolphins' social structure. Proceedings of the Royal Society of London. Series B. 268:1901-1906.

Marsh H., Eros C., Corkeron P.J. and Breen B. 1999. A conservation strategy for dugongs: implications of Australian research. Marine and Freshwater Research 50:979-990.

Marine mammal acoustics

Risch, D., Clark, C.W., Corkeron, P.J., Elepfandt, A., Kovacs, K.M., Lydersen, C., Stirling, I. and Van Parijs, S.M. 2007. Vocalizations of male bearded seals (Erignathus barbatus) classification and geographical variation. Animal Behaviour. 73:747-762.

Van Opzeeland, I.C., Corkeron, P.J. Leyssen, T., Simila,T., and Van Parijs, S.M. 2005. Acoustic behaviour of Norwegian killer whales, Orcinus orca during carousel and seiner foraging on spring-spawning herring. Aquatic Mammals 31:110-119.

Van Parijs, S.M., Corkeron, P.J., Harvey, J., Hayes, S., Mellinger, D., Rouget, P., Thompson, P.M. Wahlberg, M. and Kovacs, K.M. 2003. Regional patterns in vocalizations of male harbor seals. The Journal of the Acoustical Society of America. 113: 3403-3410.

Van Parijs S.M., Smith, J. and Corkeron. P.J. 2002. Using calls to estimate the abundance of inshore dolphins; a case study with Pacific humpback dolphins, Sousa chinensis. Journal of Applied Ecology. 39: 853-864.

Van Parijs S. and Corkeron P.J. 2001 Boat traffic affects the acoustic behaviour of Pacific humpback dolphins Sousa chinensis. Journal of the Marine Biological Association of the United Kingdom. 81: 533-538.

Van Parijs S. and Corkeron P.J. 2001. Vocalisations and behaviour of Pacific humpback dolphins, Sousa chinensis. Ethology. 107: 701-716.

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Seal stomachs VII: Aftermath



This set of posts starts here.

Once back in Tromsø, the rest of the work started. Jaws boiled in a large pot, stench-stew in a small room with its own air supply. The teeth softened from boiling, I wrenched them from jaws, cut them with a tiny bandsaw, fixed them in epoxy to microscope slides. Then I counted the rings in teeth – rather like tree-rings – telling me how old the seals were when they died.

Lotta saw to the stomachs and intestines - thawing, washing, sieving to sort contents. Dried earbones from fish, checked and measured under a microscope for species identification. Squid beaks.

Seals can live long - harps and hoods into their thirties. The youngest harp seals reach sexual maturity at four, some female hoods mature at three. Given what's known about other, better studied, seal populations with similar life histories, about a quarter of the harps and hoods in the West Ice population should have been immature.

Of 127 seals killed on the expedition, the ages of 119 were determined from their teeth. Over two-thirds were immature (and of those, 63 were yearlings). The eight animals that weren't aged from their teeth were, judged by their weight, immature as well. We had killed too many young seals, and not enough older seals, while out on the ice. And – obviously - there was nothing that could be done to remedy the bias in age classes once we were back.

Tore wanted to use the data to make inferences on the diet of harp and hooded seals in winter, and whether the diets of the two species overlapped. What he ended up with was data that could tell him a little about the diet of very young individuals of both species, and not a lot more.

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Seal stomachs VI: Seal kill



This set of posts starts here

Back into the pack ice, and another day of searching. Tore and I were on the bridge together, so I grabbed the opportunity to quiz him about the project.

“So Tore, aren't you worried about being further south than you'd intended?”

“No, I think we'll find seals here”.

“But – don't you want to get seals from the same area each year?”.

“Not really – they move north after pupping, so next year we'll be working further north anyway”.

I was getting to one of my bigger concerns.

“Hmm. Now, this project – you're looking at seasonal variation in seal diet. And you're taking them in late winter this year, summer last year, and late autumn next year, yeah?”

“Yes.”, said Tore, looking at me.

“So your data'll be temporally confounded.”.

Tore just looked at me.

“Okay,”, I said, “You get samples in winter one year, summer another, autumn another – how do you know that any differences you find will be due to the seasons, and not because something's varied between the years?”.

“But that's not a real problem.”

“How do you know? How can you tell, from this design?”

Tore just looked at me a little more, shook his head, resumed scanning for seals.

The first animal, late in the evening - we'd moved south far enough to experience a noticeable difference in time of sunset – was another grise. She was followed by three adults in quick succession, then another two youngsters. By then, it was after seven, too dark for Kjell and Bjørn to continue shooting. And it seemed that Tore had found himself a patch of dozens, perhaps hundreds, of seals.

The next morning, and I was back on the bridge, watching. Only by now, when I'd see a young seal, I'd say nothing. I wouldn't even keep my binoculars on it, in case I alerted anyone else to its presence. We'd killed nineteen animals - all hooded seals - but only a third of them had been definitely mature. At the rate we were going, the only thing that Tore would have was information on what immature hooded seals ate. I had enough problems with the whole expedition without adding an extra layer of uselessness to it.

I also had trouble with the idea that if I observed an animal, I was condemning it to death. It rather took the thrill out of observation. So I stayed on the bridge for a while, kept looking, ignoring the seals I saw. The haphazard nature of Tore's watch system paid off for the seals – I'd got my eye in, and noticed a few before the call came – someone else had seen one.

At least the ice was always beautiful. Once I saw a gyrfalcon, the pure white falcon of the Arctic. It watched us, haughty, from meagre vantages of floes, then soared away.

But I didn't see much ice for the next three days. One dead seal followed another for two days - 26, then 30 each day. By the end of both days, I needed Jan Mayen's spotlights to see what I was doing on deck.

A telling incident amid the splatter. The corpse of another pregnant female hooded seal disgorged a live pup, bleating across the deck. The crewman who'd killed the last pup clubbed this one too. Lotta was off delivering seal body parts to Tore, and so didn't see it. After he'd clubbed the pup, I looked at the crewman, shook my head, said “Et lieveling.”, just as he had before. He looked down at me, snorted, walked off. As I thought. Nothing like showing off a soft side – whether it's there or not - to impress a possibly-available woman.

And then our big day – three seals in the morning, 44 in the afternoon. The day I crushed the wounded female's skull with the sledgehammer. By evening, a dozen seals were still lined up under the glare of the deck spots for me to dissect. Kjell came to help with the dissections – it was too dark to shoot. He could skin a seal in half the time it took me.

All around me there was jubilation. Kjell and I were still working, slicing and hacking at the seal carcasses, Lotta disposing of pieces into plastic bags as needed. Tore decided it was time to celebrate, cracked open beers for everyone. Only I refused. The deck was slippery, my knife was – as always – razor sharp, and a mistake amid the bacterial soup of the dead seals didn't bear thinking about. Too dangerous for my liking.

Besides, I saw nothing to celebrate.

Once the last carcass skinned and eviscerated, chunks of gut safely stored in their plastic bags, I wiped my hands, cracked open a can of beer. After four days spent mostly bent over, manhandling, lugging over a hundred lumps of flesh weighing up to five hundred pounds, my back was beginning to ache. I'd had enough of the gore.

Next morning, when it looked like another day of killing, I had Julie find me some painkillers, spent the day reading. As it happened, only five animals were shot that day. We'd left the huge group of seals, and were heading for home. Tore was satisfied.

Continued here

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Seal stomachs V: How do we know what seals eat?



This set of posts starts here.

Stomach contents are to diet as weather is to climate. At its simplest, the accumulation of records of the weather each day – the temperature, how much rain falls - allows us to build up a picture of the climate for a particular place over time. So it is with animals' diets – if we could watch every meal that every individual of a species or population ate, then, by accumulating records of their meals, we'd have perfect knowledge of their diet. For marine mammals is this obviously impossible – unless our population of interest are all kept in captivity.

So. How do we know what seals eat? The most intuitively obvious answer would be to watch seals feeding. Then we'd know what they ate, because we'd see it happening. Logistically impossible, although technology offers hope. So. We can either find ways of looking at what our animals have ingested, or we can look at where they've gone to feed and work out what's there, or some mix of both of these. And we can do this in ways of varying sophistication.

What do seals ingest?

We can look at the contents of their stomach for recent meals; or in their intestines for slightly older material; or at their faeces, for what was in their intestine without actually handling the seals. Intestinal contents can be obtained without killing seals - they discover the joys of involuntary enemas. For seals that haul out on ice, faecal sampling presents problems that are seen as insurmountable. Enemas on ice are difficult, but not completely impossible.

And what do we do once we've removed the gut contents? There can be whole fish or squid in a stomach, or just remnant hard parts – the ear bones, backbones or ribs of fish; the beaks of squid. By sorting and measuring these back in a lab, and with access to a suitable reference collection - bones and beaks of likely prey, including examples of different sizes of the same species - we can tell what species the seal ate, and what size the prey were. Whole prey items from a stomach are easy: we can simply count, measure and weigh them. But what of hard parts? How do we allow for changes to those that we find – different bits erode in their own ways. And what do we do with hard bits that we can't identify to species, but to some higher taxon (cod-like fishes, for instance)? One way around this is to analyse the DNA of all gut contents, or of problematic goop. These analyses can be reliable and precise, but they're always time-consuming and expensive.

Or we can turn to chemistry for evidence. Chemically, seals are what they eat. Tell-tale fatty acids, absorbed from fish, shellfish, squid - or whatever else that seals might eat - turn up in seals' blubber. The chemical composition of these fatty acids, extracted from blubber samples, can, using sophisticated data-mining algorithms, be compared with the chemical composition of likely prey items. We were collecting blubber samples for Tore's colleague at the Polar Institute who did exactly this. All that's needed is a plug of blubber from the seals, and representative samples of possible prey species for the chemical analysis. And a chemistry lab and a good statistician.

Another chemical option involves comparing the relative composition of isotopes of important elements – primarily carbon and nitrogen – with representative samples from putative prey. Patterns in isotope composition provide information analogous to that from fatty acids, and can be obtained from old bones, as well as from fresh chunks of animal (skin, hair, teeth, internal organs, whatever).

Chemistry smears data over time. It offers panorama, but sacrifices detail. Stable isotopes provide insight into what an animal has been eating for months or longer, and fatty acids for weeks or months, depending on how the species under study lays down fat. But this longer perspective must have a price – it's harder to tell exactly what species has been eaten.

So it would appear that gut sampling is the best option. But detail also has its price. Fresh, just eaten food in a stomach is easy to identify. But what of animals with nothing in their stomach? What are they telling the researcher, other than that a lot of animals must die to provide data? More problematically, what about the half-digested gunk that's usually there as well? Squid beaks are chemically nothing like the hard parts of fish, and seals' stomach acids digest beaks much more slowly. How do we account for this?

Answering these questions requires addressing a far more basic one – why are the data being collected at all? Why do we care what seals eat? After all, tootling around the Arctic in an ice-strengthened research trawler doesn't come cheap. We were supposed to be addressing two questions about the foraging ecology of harp and hooded seals: how did each species' diet vary over the course of a year, and was there dietary overlap between the two species?

The question that goes begging here is – why ask these particular questions?

Because an animal's diet is the food its eats over time, the chemistry-based approaches (fatty acids and isotopes) offer the advantage of having time resolved, sacrificing detail to do so. But what of gut contents? At best, intestinal or faecal sampling provide data on meals over the past few days. So how can we make inferences about feeding over time - diet - from meals - snapshots in time?

Drawing inference from field data preoccupies ecologists. Sampling theory – how can we infer population-level conclusions from a set of field samples – drives the design of our protocols for data collection. How can we ensure, to the best of our ability, that our samples will allow us to come to unbiased conclusions about the populations of interest? It's here that a couple of key concepts come into play.

Randomization is vital. To a scientist, random means something special, something different from haphazard. In normal usage, the two are interchangeable. In scientific sampling, they are worlds apart. Random sampling is like a lotto draw – each sample has the same probability of selection. Haphazard sampling is when no thought is given to the probability of selecting a sample. Bias – the bane of being able to make inference from data – will almost certainly result from haphazard sampling, and what's worse, even if there is no bias, no-one can ever know.

Pseudoreplication is another key concept. Now that computer programs handle the grunt work of statistical analyses, there's a presumption that ecologists will collect a lot of samples of their data. These samples are supposed to be independent, otherwise they provide another source of bias when it's time to make inferences. Pseudoreplication involves collecting samples that aren't truly independent for the inferences made in the study. Like beauty or pornography, pseudoreplication can be in the eye of the beholder. Are the inferences that we make from our data appropriate? An example from the world of marine mammal stomach contents offers clarification.

A Norwegian government scientist goes into the North Sea on a whaling ship. The whalers kill a dozen or so minke whales, and the scientist checks the whales' stomachs to see what they've been eating. The whalers are interested in killing their quota of whales as quickly as possible (they're out there earning a living, after all), and find many whales in one discrete area. Most of their quota of a dozen are killed in this one spot, a few square miles across. The whales' stomachs are full of sand eels, a small fish that occurs in huge, discrete aggregations.

What inference can the scientist draw from these data? That working from a commercial vessel provides data that can be biased, because commercial considerations override a scientist's desire for randomization? Sure, and rightly so. That a large aggregation of sand eels can attract minke whales, that will feed on them? Not entirely unreasonable. What about – most minke whales in the North Sea eat sand eels? Absolutely not.

That final inference must be based on a few assumptions. The most important is that the whales killed were a representative sample of all minke whales in the North Sea. But we know - from surveys in the North Sea, and from other information on the biology of minke whales – that minkes occur elsewhere, not just in that one specific area where there happened to be a lot of sand eels. The assumption that the stomachs were a representative sample is what's known as a strong assumption – an assumption which, if it's wrong, causes everything about the study to fall apart and leaves the scientist looking like a bit of a goose.

This example – with the inference drawn that sand eels are the main food of minke whales in the North Sea – was published in a scientific journal a few years ago. The author treated each stomach as an independent sample, in order to make his inference about the whole of the North Sea. But most of the whales that were killed had aggregated to feed on the same thing (sand eels), which is why there were where they were, and so available for killing and having their stomachs investigated. So his samples weren't independent samples. Hence the term, pseudoreplicates.

Place matters, particularly when studying marine mammals that can move through entire ocean basins. So what about looking at where marine mammals feed? These days, SLTDRs are tool of choice for seals that probably can't be handled twice (like harps and hoods). There are other options for seals whose behaviour makes it likely that they can be found again – ones that return regularly to a haulout site accessible to scientists. The coolest toys for the well-heeled scientist in this situation are tiny video cameras that store digital imagery, instead of storing depth data. So finally, we can watch how seals feed. But as we can't ever be sure of re-catching a harp or hood, this isn't an option with them. SLTDRs (Satellite-Linked Time-Depth Recorders, remember?) are used, but they're kissed goodbye once they've been attached.


After our day ashore, Tore had his permission to hunt in Icelandic waters. So we all made our way back to the Jan Mayen, the ship cast off, and we steamed into Denmark Strait. Thanks to the accident while at Jan Mayen (the island), we were about to hunt seals in an area well south of where we intended to originally.

Continued here

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