Bronze sculpture?

  

A very large egg case, probably from a Big Skate (Raja binoculata), washed up on the beach on 5 February 2024.

Such an interesting design with those long curved ridges. Here are a couple more views:

  

 

 

 

 

And if you'd like to learn more, I wrote a longer post about a Big Skate egg case back in 2012 — see "Just in case" on 7 March 2012.

The Leopard vs. the Lion

Who knew that one of the most spectacular local wildlife photos of 2015 would appear so early in the year?

Jeff and Alice were observing and photographing wildlife along the shoreline of Bodega Harbor on 3 January.  They were in the right place at the right time, and Jeff had the skills to capture this amazing image: 

 

That's an adult male California Sea Lion (Zalophus californianus) catching a Leopard Shark (Triakus semifasciatus).

 

The lighting really highlights the Leopard Shark's beautiful patterning.  And you can tell from the splashing and commotion in the water that this was a dramatic moment.  Alice mentioned that there was quite a bit of thrashing and that the sea lion would sometimes toss the shark into the air!

Here's another image, showing the middle and tail end of the shark (below).  The shark's species name, "semifasciata," means "half-banded," and I think you can see why in this picture:

 

The next image is probably the best at helping you visualize the thrashing that was going on.  I wasn't sure how often sea lions ate Leopard Sharks, so I did a quick Internet search.  Several people have commented (and posted pictures or video) about seeing similar behavior in San Francisco Bay and in San Diego.  However, Jeff's pictures are much better.  Way to go, Jeff, for representing Bodega Bay and documenting a fascinating predator-prey interaction!

 

Does seeing these pictures make you wonder what happens next?  How do the sea lions consume the sharks?  Do they tear smaller pieces from them?  And where do sharks rank within the diet of a sea lion?  Are sharks preferred, or do sea lions just capture them when other prey aren't available?  Can sharks use submerged vegetation (e.g., eelgrass beds) to hide from sea lions?  Can they sense a sea lion coming?  Does the wonderful patterning of a Leopard Shark sometimes help to camouflage it from a sea lion?

P.S.  Many thanks to Jeff and Alice for sharing this story and images.

It's electric!

 

Don't worry, the bicycle rider associated with this helmet (Lewis) was not eaten by this fish!  ;)

Lewis spotted the ray washed up along the shoreline of Bodega Harbor while riding his bike...and he placed his helmet next to it for scale.

This is a Pacific Electric Ray (Torpedo californica).  It was ~3 feet long and ~2 feet wide.  It has a very distinctive shape.  Here's a slightly closer view (without the helmet):

 

Look for a variety of features: dark gray coloration; a very rounded disc with a relatively straight leading edge; a short tail with a triangular caudal fin; and two dorsal fins (the front one larger than the back one — see next image).

In the picture below, the caudal fin is broad and triangular at the far left.  The dorsal fins are located on the ridge between the rounded disc and the caudal fin (the front dorsal fin is flopped over, while the back dorsal fin is standing upright).  In this image, if you look closely at the skin of the ray, I think you'll also be able to see some smaller dark spotting which is part of the coloration of the ray.

 

Pacific Electric Rays are endemic to the northeastern Pacific Ocean.  They occur from British Columbia to Baja California, but apparently are more common south of Point Conception (preferring waters from 10-13°C or 50-55°F).

Here's a closeup of the front of the disc, showing the small eyes and the spiracles (holes just behind the eyes).  Water is drawn in through the spiracles and then passed over the gills.

Pacific Electric Rays can produce powerful electric shocks — up to 45 volts!  This is strong enough to "knock down an adult human."  They use electric shocks to stun prey and in self defense.

I don't know how common Pacific Electric Rays are in the Bodega Bay area.  Just asking around a little bit today, it sounds like they might be relatively rare here.

P.S.  Alright, this last part is only for fans of the electric slide.  I couldn't help it!  When looking at this ray today, I was reminded of the song, Electric Boogie.  Do you know it?  There are several lines that are quite appropriate when thinking about this fish:

It's electric!

(Boogie woogie woogie)

You can't see it

You gotta feel it 

Oooh, it's shocking

Now you can't hold it

But you know it's there

It's electric!

This song was written by Neville Livingston (a member of The Wailers) and performed by Marcia Griffiths (a member of the I Threes, Bob Marley's backup singers).  If you need a refresher:

http://www.youtube.com/watch?v=3PyLFzcTiYA&feature=kp

Smooth-hound?

Yesterday, 24 November 2013, County Park staff flagged me down to report a shark that had washed ashore at Doran Beach.  Although no longer alive, it was still in pretty good condition, so here's a picture:

 

The shark was ~5 feet long.  The next image shows a better side profile:

 

Note the relatively long snout and large eyes:

 

And the interesting shape of the tail fin:

 

Park staff had wondered whether this might be a Brown Smooth-hound Shark (Mustelus henlei).  Some of the characteristics seemed like a good match for that species, but there are a few others that I'm not quite sure about.  

For example, the maximum size listed for Brown Smooth-hounds is ~3.2 feet, so this shark appears to be larger.  And I don't know how consistent tail shape is in this group of sharks, but when I compared pictures of Brown Smooth-hound tails online, this individual's tail was different enough for me to hesitate.

So now I'm going to have to ask for help.  Are there any shark experts out there who can assist with this identification?  I'll circulate the photos and will report back if anyone offers additional ideas.

At least two species of smooth-hound sharks (Gray and Brown) are known to occur along the West Coast from northern California down to the Gulf of California.  Brown Smooth-hound Sharks are apparently common in shallow water bays such as Humboldt, Tomales and San Francisco bays.  Gray Smooth-hound Sharks (Mustelus californicus) occur in bays and along rocky shores.  For the record, Gray Smooth-hounds do get larger than Browns (up to at least 5.3 feet).

There is more information about both of these sharks on this California Department of Fish and Wildlife web page.

ADDENDUM (6 December 2013): Sorry it's taken me so long, but I need to update the identification of this shark!  Several experts have confirmed this as a Soupfin Shark (Galeorhinus galeus).  I had started to wonder about this when I checked Bay Fishes of Northern California (Bane and Bane 1971) because they mentioned that small Soupfins could look similar to smooth-hounds...and several of the characters looked right.  So a Soupfin Shark it is!

A day at the beach

Just a few photo highlights from a walk on South Beach in Chatham, Massachusetts, on 25 September 2013.  In order of appearance:

 

 Palm Warbler (Setophaga palmarum)

 

Wandering Glider (Pantala flavescens)

 

Tiger beetle, possibly a Hairy-necked Tiger Beetle (Cicindela sp., possibly Cicindela hirticollis).  [I don't have access to a field guide at the moment!  I'll correct this if I learn otherwise.]

 

Peregrine Falcon (Falco peregrinus) with avian prey (and trailing a dried eelgrass blade).

 

Gray Seal (Halichoerus grypus)

 

Very large unidentified ray actively feeding in shallow water near shore.  This ray was at least 4-5 feet across!  That's one tip of a pectoral fin raised above the surface.  The white coloration below the water is the ventral surface exposed whenever the ray pivoted.

 

Horned Larks (Eremophila alpestris)

 

It was a beautiful day at the beach!

A shocking discovery

 

We were walking along the inside of South Beach in Chatham today and discovered this unusual animal washed up on the sand.  You can see that it had the attention of both Eric and a young gull!

Here's a closer view from the side:

 

This is an Atlantic Torpedo Ray (Torpedo nobiliana).  I remembered that they sometimes strand on Cape Cod beaches in the fall, but I'm not sure if anyone has figured out why.  This individual was about 4 feet long.

Note the very circular shape and the relatively straight front edge of the disc.  The tail is short and the caudal fin (tail fin) is large and paddle-shaped (see below).

 

Torpedo rays are sometimes called electric rays.  They have electric organs that produce powerful electric shocks that stun their prey (primarily fish).

I found a couple of good fact sheets about Atlantic Torpedo Rays online.  If you're interested in learning more about them, check out the FLMNH Ichthyology Department web site or this page from The Shark Trust.

Ridges and grooves

Here's a fun set of mystery close-ups for you.

 

All of these images were taken under a microscope.  (There are some sand grains in the pictures, too.  For example, the amber-colored grains above.)

 

All of the pictures are from the same animal, just from different parts of the body.

 

Here's one more close-up, and then the next picture following this one will give the answer away, so consider yourself warned!

 

Okay, here we go.  Are you ready?  Do you have a guess?

 

All of the close-ups were the scales of a shark, probably a juvenile Salmon Shark (Lamna ditropis).  You can see some of the scales directly below the teeth in the image above.  I just found out about this shark at the end of the day, so I'm not sure I heard all of the details right...but it sounds like Matt and the Coastal Oceanography class discovered it on Salmon Creek Beach.

When I looked at the shark's skin with my hand lens I was so impressed with the scales that I couldn't resist taking a few pictures under the microscope to share with you (the shark was very small).  Note that some of the scales have very obvious longitudinal ridges.  It's thought that these ridges and grooves (running parallel to the water flow) reduce drag and thereby improve swimming performance.

This shark was in poor condition — it had probably been on the beach for a while and was partly scavenged and severely dried (next image).  But I've heard about a few other recent Salmon Shark strandings, so it's an opportunity to provide a little information about these events.

 

 [For scale, this shark was only ~2 feet long.]

For at least 20 years, juvenile Salmon Sharks have stranded on California and Oregon beaches in the late summer and early fall.  Until recently, the cause was unknown.  But last year, several researchers published a paper in which they discovered that stranded sharks had bacterial brain infections.  (It still isn't clear how or where the sharks acquire the bacteria.)

Schaffer, P.A., B. Lifland, S. Van Sommeran, D.R. Casper, and C.R. Davis. 2013. Meningoencephalitis associated with Carnobacterium maltaromaticum-like bacteria in stranded juvenile Salmon Sharks (Lamna ditropis). Veterinary Pathology 50: 412–417.

If you'd like to learn more general information about Salmon Sharks, check out the web pages provided by the Pelagic Shark Research Foundation and the Florida Museum of Natural History. 

Bat Ray...Bat Ray...Bat Ray

(Sung to the tune of the Batman theme song)

The wings (pectoral fins) of a Bat Ray (Myliobatis californica) disappearing below eelgrass (Zostera marina) in Bodega Harbor.

These photos were taken from the Spud Point Marina breakwater on 30 April 2012.  Because the breakwater extends 1300 feet into the harbor, it's a great place to look for marine life.

Bat Rays are found along the Pacific Coast from Oregon to Baja (and around the Galapagos).  They prefer shallow bays and estuaries, and can also be seen in kelp forests and over rocky reefs.  They are sizable fish, with a maximum width from wingtip to wingtip of ~1.8 meters (6 feet) across.

Often your first clue to the presence of a Bat Ray is the appearance of the wingtips flapping above the surface.  They are flexed upward synchronously, and look somewhat similar to the dorsal fins of sharks...but they're paired, and are floppy, more like the fin of an Ocean Sunfish (Mola mola).

 

Bat Rays feed on invertebrates — e.g., molluscs (clams), crustaceans (crabs, shrimp), and worms.  They use their pectoral fins and prominent snout to dig pits in the mud, exposing invertebrates below the surface.

While observing them recently, it was fun to follow the clouds of sediment in the eelgrass bed as the rays were feeding (it reminded me of watching bubble clouds created by humpback whales).

 

Bat Rays have unusual teeth — they're flattened and hexagonal in shape, ideal for crushing and grinding (imagine trying to break a clam shell in your mouth).  It's worth looking at this picture of a Bat Ray jaw and teeth (scroll down to the 5th image).