sharks and trans-Tasman lost waterfowl

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andrewcrossland
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sharks and trans-Tasman lost waterfowl

Postby andrewcrossland » Tue May 21, 2019 11:10 am

Some time ago someone suggested that lost waterfowl crossing the Tasman could be easy pickings for sharks if they settled on the water. I don't really have any opinion on the matter other than the image of sharks seizing hapless swans in mid-ocean has stuck in my mind. Or maybe that's from watching a documentary on sharks doing this very thing to young albatross off a breeding colony in the North Pacific,

Anyway, yesterday off the southern side of Banks Peninsula there were 2 Black Swans sitting on a stormy sea, maybe half a mile offshore. A Giant petrel seemed intrigued by them but no sharks seen in 15 minutes of watching.

Another observation - 3 or 4 years ago at Flea Bay on Banks Peninsula I saw a goose sitting on the water in the middle of the bay and the water was crystal clear. A shark duly appeared and swam underwater pretty close to the unsuspecting goose. But then the shark went deeper and didn't reappear. One lucky goose!
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zarkov
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Re: sharks and trans-Tasman lost waterfowl

Postby zarkov » Tue May 21, 2019 6:16 pm

It's probably a statistical improbability, most sharks don't usually predate on sea birds resting on the surface or there'd be a lot fewer shags, gannets etc.

Also, as a regular sea kayaker I try to persuade myself that I'm unlikely to meet a fish bigger than me.

It's worked so far.
Raewyn
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Re: sharks and trans-Tasman lost waterfowl

Postby Raewyn » Tue May 21, 2019 8:55 pm

Sharks aren't always hunting. Last December up at Spirits Bay I sat on the island watching one of two bronzies cruising around. When I saw a school of mullet heading towards the shark I expected some action but they all just swam on by (http://www.raewyn-adams.nz/blog/bronze-whaler-2). Coming back to birds, up at Spirits the pied shags fish well out at the point where the sharks harass the fishermen's catch, but don't seem to bother the birds.
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zarkov
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Re: sharks and trans-Tasman lost waterfowl

Postby zarkov » Tue May 21, 2019 10:44 pm

You'd think there would be a shark species that would specialize in feeding on sea birds, but generally they don't seem to.

A pelagic guide at Stewart Island told me that when sea birds feeding on chum behind the boat lift off the surface, it's because they've seen a shark, but the dynamics are different down there.

Up North they don't seem bothered.

Image from a Tutakaka pelagic trip reported here, that I can't find.
Wandering Albatross & Blue Shark_Tutukaka Pelagic_Oct18_FB_IMG_2441.jpg
Wandering Albatross & Blue Shark_Tutukaka Pelagic_Oct18_FB_IMG_2441.jpg (491.52 KiB) Viewed 675 times
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ourspot
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Re: sharks and trans-Tasman lost waterfowl

Postby ourspot » Wed May 22, 2019 7:19 am

I took that image of the blue shark with the albatross on last years October Tutukaka Seabird Pelagic trip. That shark was just slowly cruising along and went right up to the albatross and then the albatross just fended it off with it's foot to the shark head and the shark moved away. The albatross just stood it's ground the whole time - aware of where the shark was but making minimal effort to avoid it. A little later we had a stunning sight of the same shark and the albatross having a short tug of war over a whole squid - was amazing to see (unfortunately no one managed a photo).

We've had the odd shark (either blue or mako) turn up off the back of the boat when chumming and in general they are very chilled and cruising along, more interested in the chum bag than any birds. And generally the birds don't seem bothered by them.

But on the trip last weekend we had a mako shark turned up and it was a lot more agitated and aggressive in behaviour than I've seen before, and would heading directly to birds or sometimes coming up under them. The birds (big and small) were definitely keeping their distance from this shark and would lift off and settle down further away anytime it approached near them. On this occasion it seemed the birds could tell the mood of this shark and behaved accordingly to avoid being attacked. Luckily the shark didn't hang around too long.

Also a few years ago I saw a Mute Swan sitting out on the open ocean past the breakers, approx 100 metres beyond the main stack at the Muriwai Gannet Colony - hope that one didn't succumb to one of the sharks the area is know for.

Cheers Scott
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David Riddell
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Re: sharks and trans-Tasman lost waterfowl

Postby David Riddell » Wed May 22, 2019 9:34 am

Hopefully the below will be a link to a short video from a pelagic in Hawke Bay, June 2016 (thanks Russ!) showing an interaction between a northern giant petrel and a blue shark around the berley bag at the back of the boat. A clearly hungry shark and a quite unconcerned bird - though perhaps in other situations the interaction might go differently.

https://photos.app.goo.gl/kwip3NcKAudcLn1S7
Ian Southey
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Re: sharks and trans-Tasman lost waterfowl

Postby Ian Southey » Wed May 22, 2019 12:36 pm

Maybe some sharks are more dangerous than others but I have seen pictures of birds, prions I think, taken from a Kingfish stomach. Can't remember where...

Ian
Colin Miskelly
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Re: sharks and trans-Tasman lost waterfowl

Postby Colin Miskelly » Thu May 23, 2019 8:13 am

This study suggests that wayward land birds (presumably waterlogged and struggling on the surface) are more likely to end up as shark bait than seabirds:

https://www.sciencealert.com/shark-spew-study-shows-they-ve-been-eating-something-really-weird?fbclid=IwAR0E9TodGoSAjn58t2qPkYfetQtF2T9dYptdYebpJskWhZH8_KWUr2KrkLg

Ngā mihi
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Davidthomas
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Re: sharks and trans-Tasman lost waterfowl

Postby Davidthomas » Thu May 23, 2019 8:18 am

Ian Southey wrote:Maybe some sharks are more dangerous than others but I have seen pictures of birds, prions I think, taken from a Kingfish stomach. Can't remember where...

Ian



Hey Ian,

I remember also seeing the same photo although I think they were fluttering shearwaters mostly rather than prions. Either that or we’re both thinking of different photos! Equally possible given how voracious predators kingfish are.
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ourspot
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Re: sharks and trans-Tasman lost waterfowl

Postby ourspot » Thu May 23, 2019 2:05 pm

Not a shark, and not in New Zealand but check out this vid of Giant Trevally catching Terns in mid-air. Thats some skilled predation. The best action is from 1 min on.
https://www.youtube.com/watch?v=h4pxLHG0Wzs

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