Blue Glaucus - Lang’s Beach

Discuss natural history subjects not strictly related to birds. Reports of interesting mammal, reptile, and invertebrate sightings are welcome.
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Studio Pajaro
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Blue Glaucus - Lang’s Beach

Postby Studio Pajaro » Mon Mar 29, 2021 5:42 pm

Hundreds of live Blue Gaucus have washed up on Lang’s Beach, Northland. Also Blue bottles, purple seashells and some other purple slug type creature.
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Finn Davey
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Re: Blue Glaucus - Lang’s Beach

Postby Finn Davey » Mon Mar 29, 2021 8:20 pm

Oh, they're beautiful!

I didn't know we get them in NZ
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David Riddell
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Re: Blue Glaucus - Lang’s Beach

Postby David Riddell » Tue Mar 30, 2021 11:02 am

I once saw something very similar, in January 1998 or '99 at Cook's Beach, after a period of about 10 days of strong easterly winds. There were hundreds of Glaucus all along the beach, as well as many other pelagic sea-surface creatures, including the two in the top photo. The more elongated one at the bottom is a by-the-wind sailor (Velella velella) - these are colonial hydrozoans distantly related to Portuguese men o' war (also present at Cook's Beach), though much less toxic. The other is a close relative of Velella called a blue button (Porpita porpita), which have a more tropical distribution and are much less commonly seen in NZ. The purple seashells will be species of Janthina, or violet snails. The commonest in New Zealand is usually J. violacea, but there's a smaller species, J. exigua which also comes ashore quite often. Oddly the commonest species that day at Cook's Beach was a much more bulbous snail, J. globosa, which is normally much scarcer than the other two.

Among the other creatures that came ashore that day were oceanic crabs, Planes minutus, which cling to floating seaweed and other debris. There were also a couple of other seaweed-dwellers - pale blue isopods (Idotea metallica) and a small pale nudibranch with two rows of gills down its back, called Fiona pinnata. And there were lots of juvenile flying fish cast up on the beach as well. Some of these were still swimming along the shore, and a few had washed into the little stream at the end of the beach, which produced the bizarre sight of flying fish swimming alongside whitebait!

This kind of event happens quite rarely in NZ, though Glaucus occasionally washes up in ones and twos - several iNaturalist records in the last few years. There was a mass stranding of this and associated species reported on iNaturalist about five years ago, which was written up as a short journal entry - link below. The community was dubbed the "Blue Fleet' by Sir Alister Hardy, one of the grand old men of open ocean natural history - a very appropriate name since so many of them are some shade of blue.

https://inaturalist.nz/journal/tangataw ... -otaipango
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Studio Pajaro
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Re: Blue Glaucus - Lang’s Beach

Postby Studio Pajaro » Tue Mar 30, 2021 5:26 pm

Hi David,
Thanks for that information. That is very interesting! Blue Fleet is definitely the perfect description.
I have often seen the Blue Bottles and Janthina seashells, but never any of the other species.
Cheers!
Wade
Raewyn
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Re: Blue Glaucus - Lang’s Beach

Postby Raewyn » Wed Mar 31, 2021 6:13 pm

This article (https://www.sunlive.co.nz/news/265486-b ... goers.html) was in our local (Bay of Plenty) media today and I had a chance for a look at the Mount Beach this afternoon. Walking from Mauao to Moturiki Island about 3pm I saw three tiny Glaucus along with a number of also tiny bluebottles - all about 1-1.5cm. Also 2 slightly larger Velella. It was and hour or so before low tide and they were all spread out in a line about mid-tide.
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Re: Blue Glaucus - Lang’s Beach

Postby Raewyn » Wed Mar 31, 2021 8:36 pm

Adding some photos. The lower one is Glaucilla bennettae instead of Glaucus atlanticus.

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