I’m back from a week’s holiday including a visit to Seal Rocks about 300 kms north of Sydney.
The sleepy fishing town gets its name from the rocky outcrops occasionally inhabited by Australian Fur Seals, Arctocephalus pusillus ssp. doriferus. This is about as far north as the animal ventures in Australian waters.
View from the Sugarloaf Point Light House, 11th January 2007
I didn’t see any seals during my visit.
The main population of Australian Fur Seals apparently breeds on islands in the Bass Strait between Tasmania and Victoria. That’s a long way from the mid north coast of New South Wales.
There is a second subspecies, the Cape Fur Seal (A. p. pusillus), with a southern African distribution including the west coast of South Africa and Namibia.
Seals are apparently still hunted in southern Africa, hunting has been banned in Australia since 1923.
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Many thanks to Neil Hewett for looking after the blog in my absence.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
I have sailed around those, pretty amazing with all those basking seals.
Seal Rocks is a weird place, lost of fishos with two thumbs, Deliverance by the Sea.
If you travel west a few hours you will end up at Barrington, from sandy beaches through temperate rainforest to alpine snow country.
These things always amaze me, we take them from granted.
Welcome back Jen!
Namibia has the world’s second largest seal hunt in the world, Cape fur seals are slaughtered, according to NGOs in a most inhumane way.
About 91000 Fur seals killed in 2006.
Listed on CITES Appendix II.
Glad that Australia has banned the seal hunt.
Rog, We drove west up to Dungog on Saturday – through Stroud. And I was in Armidale yesterday – drove west from Bellingen. I was surprised at how green the countryside was.
Ann, 91,000 is a huge number! How big is the population in southern Africa?
There is evidence there was once a breeding colony of Australian fur seals at Seal Rocks, NSW, but they are certainly not regularly present there anymore. There is another Seal Rocks, in Bass Strait, which is a breeding colony. The species has been recovering from when we used to harvest them in Australia, and can be found hauled out during winter and spring along the east coast from time to time. They are also routinely shot by fishermen.
Seal Rocks has been the site for a number of cetacean mass strandings. The last was one I attended in 1992, when some 50 false killer
whales came ashore.
On the terrestrial front, pockets in the area are rich in wildlife.
Big thanks to Neil for his caretaking. You did a great job Neil.
I should also add (at risk of multiple posting) that just offshore you can usually see Grey Nurse Shark, an endangered species, if you go diving.
Jen,
IFAW states that numbers are about 1,5 to 2 million south African fur seals.
They are also listed as ” Lower threat” on the IUCN list.
Seals are culled for the fisheries sake. In South Africa as well to save sea bird eggs( never heard about this).
Fur seal pelts and penises are sold mainly to Asia.
Seems controversial if the hunt is sustainable or not…
Seems like the south African fur seal is listed as ” Lower Risk” on the IUCN list.
Welcome back Jen: Neil did a great job holding the fort; pity you have to interrupt him hey
Seals in Bass Strait are apparently on the increase and should overflow back round the coast to their old haunts eventually. Commercial salmon farmers down the south end of Tasmania can do with out them though.
90,000 cull out of a 1.5 million population of a species that, presumably, mates annually is hardly “controversial” or close to “unsustainable”, Ann.
How long do they live for and how old are they at breeding age?
Ian, the reason why some NGOs call the hunt ” controverial” is because population is declining and hunting quotasare increasing among a population that has high pup mortality.
Mass die-offs have also occured in 1994 and 2000 and the population has obviously not reached its original numbers.
Why I’m personally against some marine mammal hunts , is the science behind these.
Does a removal of a top predator really help to improve fisheries?( I have an understanding to remove some problem individuals).
In Norway , some culling of coastal seals, mainly grey seals are based upon they pose a threat local fisheries as well as they are infected by a parasite, the sealworm, which in turn is a parasite in some fish, mainly cod.
Ian, fur seals reach sexual maturity between 3 and 6 years, however , it seems like they don’t mate until they are 12 years old.
I did some googling on this as well, Ann, but found no reference to only mating by year 12. What I saw was female sexual maturity at 3-4 years with males not getting to mate until 10 to 12 years.
This was because they needed full maturity to be dominant enough to win and maintain a harem of 6 to 10 females under constant threat from randy interlopers.
Life expectancy 19 to 20 years. The key to the high pup mortality rate would appear to be the early age of independence at 4 to 6 months.
In any event, at 20 year life cycle there will be approximately 5% of population in each age cohort, of which 2.5% will be males.
And assuming an equal number of years of female post breeding age that means 12/20 years of breeding age and, at 85% annual fertility, means about 25% annual birth rate with a rapid decline in age cohorts to 5% each.
We can also assume that the larger males will have a lower pup mortality rate than females which will slightly skew the numbers to show a higher proportion of adolescent males which will reduce as they begin combat for harems.
With harems of from 6 to 10 females to one dominant male, it means that 90% of young males will be surplus to intergenerational requirements.
So, assuming a static population, a cull of 2.25%, being young mature males, and another 2.25% of post breeding females, would have only minor implications for maintaining population levels. In fact, such a cull would tend to reduce combat mortality and extend the dominance of the strongest males in the same way that Bulls in cattle herds have benefited from the reduction in competitors.
The removal of surplus males would also improve the pup survival rate significantly as it is my understanding that many pups are killed by jealous, excluded males and newly dominant ones who destroy the legacy of the defeated Bull to make room for his own progeny.
Some 4.5% of a population of 1.5 to 2.0 million is 67,500 to 90,000 each year. So given the beneficial effects on pup survival of targeted culling there appears more than adequate grounds to conclude that the current range of annual culls, from 50,000 to 90,000 a year depending on circumstances, poses no threat to the population.
And this is born out by the population data itself which shows no significant changes over recent times. The actual numbers explain why but I would welcome any more accurate data that would indicate otherwise.
Well Ian, the harsh reality is that most seals culled seem to be pups, so don’t think your calculations on post breeding cows and young male seals is something we can calculate on…
Even if this hunt is ” sustainable” according to your figures, the matter boils down to some other questions that are as important as this sustainability issue.
There is a market in Asia for the bull’s genitals, a much smaller market for fur …but what about the seal meat??? Yeah, no market for this product, since the meat is unpalatable…
Is it justified to carry out a big culling and not utilise all products?
The trend is similar in the whole world… seals are culled, but the fur, meat in some cases are dumped.( Norway). Very soon there will be zero market for seal products in the EU ( except for Greenland seal products).
Do we think it is justified to cull the seals for the fisheries sake ( no science backup) and sell bull’s genitalia to Asia???
It would seem the surfing (ice) bears are not doing their job. Perhaps some brown bears could be sent to Namibia.
And thanks, Ann, for the info that most of the cull is pups. This makes the current cull figures even less risky because the annual birth rate is about 25% of the population, or 375,000 to 500,000 pups a year. And as the pup mortality rate is already at 80% then four out of every five pups will die anyway.
And that means that 80% (72,000) of the 90,000 culled animals would have dies anyway from other causes. Which means that only 18,000 may have survived without culling, assuming no substitution effect.
What this all means is that the impact of this culling is well within the normal range of variation. If numbers have been known to collapse due to environmental /seasonal factors then a close to 100% infant mortality is within the normal range and easily recoverable with a 25% annual birth rate.
And as for Bulls genitalia, I think that market has recently been penetrated, as it were, with cheap Viagra.