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Tuesday, August 23, 2016

A rare "op-portunid-y"

Yesterday Jason mentioned he had found something exciting.  He gave me a chance to guess what it was, but I struck out.  He and Ted had been trapping crabs in Tomales Bay for a research project, and discovered an unexpected species.

If you're familiar with local crabs, you'll probably recognize that this is not a species that we usually find in the Bodega Bay/Tomales Bay area. 

Keep in mind that this summer follows two warm-water years ("The Blob" in 2014-2015 and El NiƱo in 2015-2016).

Did you notice the rounded, flattened, paddle-like legs in the photo above?  The paddles are used for both swimming and burying in the sand (and are a characteristic of the swimming crabs, Family Portunidae).
Here's another photo of this striking crab, this time from below:

This image emphasizes the impressive length of the claws.  And isn't that purple color amazing?!

From the front you can see the spines on the claws and on the carapace.  (For those of you who have spent time on the East Coast, you might have noticed a similarity to a blue crab.)

Meet Xantus' Swimming Crab (Portunus xantusii)!  This species has a more southern distribution, with most records occurring south of Morro Bay.  They were recorded in Monterey Bay in June 2016 (see story here), and there are a few iNaturalist records from San Francisco Bay in March 2016 and June 2016.

Since these crabs have planktonic larvae, it's likely that larvae reached this area in either 2014 or 2015 (based on their relatively large size, I'm leaning towards 2014).  The crabs survived and are now being discovered in sandy/muddy habitats far to the north of their normal range.

Jason and Ted found four Xantus' Swimming Crabs near Sacramento Landing in Tomales Bay.  It would be great to hear about any other sightings, so if you see one of these crabs, take pictures, measure the width of the carapace, and let us know.  This is a rare opportunity to document Xantus' Swimming Crab in northern California.

Here's one more pictureJason smiling about his exciting discovery!

Monday, August 22, 2016

Long wings and feathers like scales

Wonderful views of two juvenile Baird's Sandpipers (Calidris bairdii) feeding along the wrack line on Salmon Creek Beach tonight (22 August 2016).  At one point, they walked right by us!

For a little more information about Baird's Sandpipers and their amazing migration, see the post from 3 August 2013.

Sunday, August 21, 2016

Tucked in

Juvenile Western Sandpipers (Calidris mauri), roosting on the outer coast at high tide, 20 August 2016

Friday, August 19, 2016

Like pepper

Recently we noticed an amazing number of juvenile periwinkles (Littorina spp.) in the high intertidal zone.  It must have been a very good year for them!

These young snails are tiny.  I should have taken a picture showing an entire rock but there were so many little black snails scattered across the boulder that it looked as if someone had shaken pepper all over the rock!  Note how the snails are concentrated along the edges of and in between the barnacles.  Do you have ideas about why that might be?

If you haven't seen periwinkle embryos before, here's a picture taken under a microscope:

Adult female periwinkles release transparent capsules containing fertilized eggs into the water.  The eggs and embryos develop for about a week and then emerge from the capsule as free-swimming planktonic larvae.  Eventually the swimming veligers will undergo metamorphosis and settle onto the bottom as tiny snails.

Wednesday, August 17, 2016

Diving and surfacing

Nice views of Humpback Whales from the boat trip to Cordell Bank on 14 August 2016:

In the last picture, one whale has just surfaced (on the left, you can see the mound-like splashguard surrounding the blowhole and the spray from the exhalation), and a second whale is diving (on the right, with flukes raised).

Monday, August 15, 2016

Cooler water

We only had a couple of dolphins visit the boat yesterday near Cordell Bank.  But the sighting is notable as they were Pacific White-sided Dolphins (Lagenorhynchus obliquidens).  

I don't get out on pelagic trips that often, but during the last two years, while ocean temperatures were warmer, I only saw Common Dolphins (Delphinus spp.).  With cooler water temperatures this year, perhaps the species have shifted back to the more expected dolphin for this area.

For the record, here's a documentary shot of a Pacific White-sided Dolphin from yesterday:

And a better shot from a trip in October 2011:

Sunday, August 14, 2016

"Ocean runners"

Ashy Storm-Petrel (Oceanodroma homochroa), above, and two Fork-tailed Storm-Petrels (Oceanodroma furcata), below

Photographed at Bodega Canyon, ~18 miles offshore, 14 August 2016

P.S.  Their genus, Oceanodroma, means "ocean runner," likely for the way they can appear to be running on water (flying low and sometimes pattering their feet on the surface of the ocean).