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Keishu Asada

@cephwarden.bsky.social
1.3K followers 83 following 541 posts

A warden of Sand Quentin. Videographer and photographer, mostly of marine wildlife. Marine Fieldwork Specialist at the Okinawa Institute of Science and Technology (OIST), Marine Science Section.

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Keishu Asada @cephwarden.bsky.social · 6h
Not good footage, but this is the closest I've been to a cutlassfish, a denizen of deeper, open waters that is very rare to see close to shore. When idle, they orient vertically, head facing up.
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Keishu Asada @cephwarden.bsky.social · 27/09/2026
Baby sweetlips fish dance like no one's watching
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Keishu Asada @cephwarden.bsky.social · 24/09/2026
It's like if they tied a person to the front of a Predator drone in order to absorb enemy fire 😅
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Keishu Asada @cephwarden.bsky.social · 23/09/2026
One of my favorite nudibranchs, Bornella anguilla, swimming like some sort of psychedelic dragon
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Keishu Asada @cephwarden.bsky.social · 17/09/2026
Among the hustle and bustle at the knee-deep water's edge, a seahorse casually pretends to be detritus as it moves away from the stomping feet
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Keishu Asada @cephwarden.bsky.social · 03/09/2026
A tiny dragonet creeps past a real dragon of this rock - a camouflaged stone fish
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Keishu Asada @cephwarden.bsky.social · 24/08/2026
A pair of young broadclub cuttlefish hanging out together. Shows off some hunting behavior.
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Keishu Asada @cephwarden.bsky.social · 17/08/2026
The camouflage of Octopus cyanea
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Keishu Asada @cephwarden.bsky.social · 13/08/2026
Worms like gummy bears swimming up to the surface to spawn. They are probably not complete polychaete worms, but instead, segments that detach and swim away from the main body just for spawning, while the actual worm stays safe and snug in its den somewhere below.
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Keishu Asada @cephwarden.bsky.social · 10/08/2026
An Octopus cyanea, hiding under your very nose. I'll put the reveal photo in the comments.
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Keishu Asada @cephwarden.bsky.social · 09/08/2026
For the last three weeks or so, I've been assisting a camera crew for NHK who came to film a nature documentary on cephalopod camouflage. Their main camera is so heavy it takes two to carry it to the water. All this work will amount to ... about 3 minutes of footage in the show airing in late 2027.😅
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Keishu Asada @cephwarden.bsky.social · 06/08/2026
I dig this
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Keishu Asada @cephwarden.bsky.social · 05/08/2026
Hard to remember waves even exist on a day like this, from a few days ago. Now, a typhoon fast approaches and will hit tonight. Some models show up to 12m swell not far off shore.
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Keishu Asada @cephwarden.bsky.social · 29/07/2026
The elegance of reef squid
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Keishu Asada @cephwarden.bsky.social · 29/07/2026
A coral polyp, open alone in its colony, looking like a rose
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Keishu Asada @cephwarden.bsky.social · 27/07/2026
A polychaete worm like some great spiny four-eyed dragon
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Keishu Asada @cephwarden.bsky.social · 27/07/2026
An octopus decloaks
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Keishu Asada @cephwarden.bsky.social · 25/07/2026
Flying foxes! Hanging out and eating fruit.
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Keishu Asada @cephwarden.bsky.social · 22/07/2026
Emerging from a sandstorm with a tail held high like a banner. A rare cowtail ray.
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Keishu Asada @cephwarden.bsky.social · 20/07/2026
A pteropod, fairylike, ascending into the sunshine
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Keishu Asada @cephwarden.bsky.social · 20/07/2026
Reef squid shimmering through sunlight
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Keishu Asada @cephwarden.bsky.social · 20/07/2026
In a shallow sunlit channel I came across an area where the rocks were all purple. At first I thought it was just crustose coralline algae, but a closer look revealed that it was all eggs! Apparently a nursery for scissortail sergeant damselfish, who seemed to be the ones tending to them.
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Keishu Asada @cephwarden.bsky.social · 16/07/2026
Exploring an unfamiliar area and greeted by a large white tip reef shark
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Keishu Asada @cephwarden.bsky.social · 16/07/2026
A Callistoctopus walks through a plankton storm brought on by our lights, arms up in a suspicious defensive posture.
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Keishu Asada @cephwarden.bsky.social · 15/07/2026
There were a lot of these in June. Baby octopuses drifting on rafts of sea grass, each off on some grand voyage.
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Keishu Asada @cephwarden.bsky.social · 14/07/2026
Seen one of these for the first time today, but what is it? Just a common sea snake? No! It's a banded snake eel or harlequin eel. They mimic venomous sea snakes as a defensive strategy. They also have very cute goofy faces but I was sadly unable to get close.
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Keishu Asada @cephwarden.bsky.social · 13/07/2026
A large uncommon larvacean I refer to as the barrel oik. Most larvaceans live in a spherical mucous 'house' for filtering plankton. This one's house (almost totally invisible here) is barrel-shaped with a clear directionality of movement and even 'intakes' in the front like a biological jet engine.
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Keishu Asada @cephwarden.bsky.social · 13/07/2026
A young cuttlefish (Ascarosepion latimanus) in just ankle-deep water, right on our marine station's doorstep. Watch it show off some dramatic shifts in body patterns!
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Keishu Asada @cephwarden.bsky.social · 09/07/2026
Its presence heralded by a dust cloud of its own creation... who could it be!? (A very rare cowtail ray!)
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Keishu Asada @cephwarden.bsky.social · 09/07/2026
Exquisite labyrinthine texture of a coral
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Keishu Asada @cephwarden.bsky.social · 30/06/2026
Divers and coral spawn are not the only things looking to have a romantic evening on the night of the full moon... Fireworms coming to surface to spawn.
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Keishu Asada @cephwarden.bsky.social · 29/06/2026
It's not often I see an upside down jelly actually swimming in the water column.
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Keishu Asada @cephwarden.bsky.social · 25/06/2026
Been puzzling over this swimming beer hop/artichoke for a few days. The video quality is poor because I was at the surface and without my best lights. I think it's the sea slug Cyerce blackburnae, although the swimming style doesn't fit what it says in the description (from just last year).
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Keishu Asada @cephwarden.bsky.social · 23/06/2026
Moray yawning in its cozy den
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Keishu Asada @cephwarden.bsky.social · 22/06/2026
An octopus against the moon
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Keishu Asada @cephwarden.bsky.social · 09/06/2026
An Octopus cyanea moves through the reef, presumably pondering octopus thoughts
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Keishu Asada @cephwarden.bsky.social · 08/06/2026
A stonefish in magnificent purple and orange... Not blending in at all. You do you.
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Keishu Asada @cephwarden.bsky.social · 08/06/2026
Cathedral skylight
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Keishu Asada @cephwarden.bsky.social · 06/06/2026
A manta coming over the crest at a cleaning station on Kume. It's not in the shot, but there were a mating pair of octopuses that crept up to the top and just went out of view. It would have been great to have them all in the same shot!
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Keishu Asada @cephwarden.bsky.social · 05/06/2026
A nudibranch standing at attention! I think it is waiting for the current to pick it up so it can drift away somewhere farther than its foot can carry it.
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Keishu Asada @cephwarden.bsky.social · 04/06/2026
#marinelife
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Keishu Asada @cephwarden.bsky.social · 04/06/2026
The day octopus (Octopus cyanea) camouflaging on the reef
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Keishu Asada @cephwarden.bsky.social · 03/06/2026
The dreamlike movement of water. At Akame Forty-Eight Falls, Mie Prefecture, from a couple of months ago. We had hoped to get a glimpse of some giant salamanders but no luck.
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Keishu Asada @cephwarden.bsky.social · 02/06/2026
An Octopus cyanea on the reef.
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Keishu Asada @cephwarden.bsky.social · 30/05/2026
Shark guarding the entrance of a cave I call the cathedral. This spot has always felt like a perfect place for white tip reef sharks to be hanging out but it's so rare to see one actually here.
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Keishu Asada @cephwarden.bsky.social · 25/05/2026
A sea elephant (heteropod). Such a strange and enchanting creature. It is technically a type of swimming snail.
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Keishu Asada @cephwarden.bsky.social · 25/05/2026
There are three stonefish in this picture. At a rock I call the stonefish fortress. The most I have seen on this rock is nine.
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Keishu Asada @cephwarden.bsky.social · 21/05/2026
There's something mesmerizing about the way this marauding Acotylean flatworm flows over the across the terrain, like a liquid with frills.
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Keishu Asada @cephwarden.bsky.social · 21/05/2026
One of my all time favorite nudibranchs, Bornella anguilla. Like a harlequin patterned dragon soaring through its little domain
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Keishu Asada @cephwarden.bsky.social · 20/05/2026
We have a new little paper out in Marine Biology about the first report of the mitre squid, Uroteuthis chinensis, reproducing in the waters of Okinawa, Japan. Here's a little thread with videos about the encounter in the field: link.springer.com/article/10.1...
link.springer.com
Reproduction of Mitre squid, Uroteuthis chinensis, in Okinawa - Marine Biology
Despite the importance of Mitre squid, Uroteuthis chinensis, as a fishery resource in the Western Pacific, there have been limited research conducted on their biology. Here, we present observational e...
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