Three in a row

 

Three Ocean Sunfish (Mola mola) on an offshore trip to Cordell Bank on 14 October 2018.

These individuals are on the smaller side.  For a few more photos of larger Ocean Sunfish, check out the post from 24 August 2014.

 

Eye of the sun

 

We didn't see many Ocean Sunfish (Mola mola) on our September 6th boat trip, but this one was close to the boat.  Note the very large eye, and the interesting skin pattern.  [Click on the picture for a slightly larger version.]

For views of an entire sunfish, see the post from 24 August 2014.

I'll be posting a few more pelagic trip photos, so stay tuned!

A sign of warm water?

I've heard a few reports of Ocean Sunfish (Mola mola) recently — a couple washed up on local beaches (see below), and Lewis saw one swimming at the north end of Bodega Harbor yesterday (near Whaleship Road)!  I don't know how often they enter Bodega Harbor — do you?

This relatively small sunfish was photographed on Salmon Creek Beach on 14 June 2015:

 

Ocean Sunfish are often associated with warmer water.  Although sea water temperatures have dropped down to 10.5°C (51°F) during the last couple of days, just before that they were up to 15.5°C (60°F).  It'll be interesting to see how warm the ocean gets this summer.

Subsidy

About a week ago, while driving into work, I noticed a few Turkey Vultures (Cathartes aura) feeding in a grassland.  By itself that sighting wasn't unusual, but the exact location was a little odd — I hardly ever see vultures feeding there.  It was close to the road, so I decided to walk out to take a look at what they were feeding on.

 

I expected it to be some sort of mammal or bird...but my eyes opened wide to see this:

 

An Ocean Sunfish (Mola mola)!  The vultures were eating this Ocean Sunfish in a grassland at least 120 feet from the bluff edge!

So one of the first questions is, how did the sunfish get there?  It's seems unlikely that a vulture could lift such a large prey item.  It's more likely that the sunfish washed up on the beach, and then a mammal (e.g., Coyote?) carried it into the grassland.

As I was photographing the sunfish, I noticed some movement along one edge.  Looking more closely, I realized an insect with strong black and yellow markings was landing on a torn area of the sunfish:

 

I don't have a lot of experience identifying insects in this group, but I think this might be a Western Yellowjacket (Vespula pensylvanica).  Please correct me if I'm wrong.

The yellowjacket was actively carving out a piece of the sunfish!  Here's a sequence of images documenting the event, until just before the yellowjacket flew off with its prize:

 

 

 

This is a very nice example of a spatial subsidy — "movements of nutrients, detritus, prey, and consumers among habitats" — as defined by Gary Polis and colleagues in 1997. (See Polis, G.A., W.B. Anderson, and R.D. Holt.  1997.  Towards an integration of landscape and food web ecology: The dynamics of spatially subsidized food webs.  Annu. Rev. Ecol. Syst.  28: 289-316.)

Inspired by the work of Gary Polis, ecologists have been increasingly interested in the movement of resources and energy between distinct ecosystems — such as from the sea to the land.  In this case, the Ocean Sunfish, normally found in the open ocean, was washed up onto a sandy beach, and then probably carried by a terrestrial mammal to a coastal grassland where it then served as food for land birds (vultures) and terrestrial insects (yellowjackets).  I couldn't help wonder — how often do yellowjackets eat Ocean Sunfish in grasslands?

Fins and feeding at the surface

 

Seeing a fin like this out at sea always requires a close look — is it a shark, or something else?

If the fin sculls from side-to-side and occasionally flops over, then it most likely belongs to one of these:

 

This is an Ocean Sunfish (Mola mola), one of the largest (= heaviest) of the bony fishes.  Although most individuals are ~3-5 feet long and weigh 175-500 pounds, the largest recorded was nearly 9 feet long and tipped the scale at just over 5,000 pounds!  

If you haven't seen one before, Ocean Sunfish might be hard to figure out at first.  Their anatomy is unusual.  The caudal (tail) fin has been reduced to a ruffled flap along the trailing edge, so the fish looks dramatically truncated.

The most noticeable fins are the dorsal and anal fins — they're the tallest fins and are used for swimming.  If you're looking for them, the pectoral fins are also visible at times — they're short and rounded, located behind the eye.  Here's a picture that shows all of the fins I just mentioned (the sunfish is lying on its side at the surface):

 

The image above also shows the overall rounded and laterally compressed shape of Ocean Sunfish.  This shape is alluded to in their scientific name — "Mola" means "millstone."  

The mouth of an Ocean Sunfish is relatively small (this is a head-on view):

 

But I mention it because we saw them feeding on By-the-wind-Sailors (Velella velella) last week!  

Below are two pictures in a feeding sequence.  The first shows a sunfish approaching a Velella from below.  In the second, the sunfish has just finished inhaling the Velella.  (Note that it appeared to be using its rounded pectoral fins to steer.)

 

 

I'll leave you with one last shot of this wonderful open ocean fish.  Watch for them this year as there seem to be quite a few around, perhaps associated with the warmer ocean water.

 

All photos from Monterey Bay on 22 August 2014.