It feels like forever since I've checked in on the cormorants at Natural Bridges. I simply haven't had time to mosey down there, take a gajillion photos, and then deal with them on the computer. But today I thought I'd give myself until lunch time to play with photos and such, before I hit the grindstone again and work on a lecture about the natural history of Big Sur.
And for the update: The Brandt's cormorants (Urile penicillatus) chicks are growing up! They're still mostly fluffy but some have a few feathers, and they're getting big now. I watched for about half an hour before realizing that the parents were feeding them; after that it was pretty easy to see when a feeding was imminent.
First, there's the behavior of the chick(s). Most of the time they are flopped like sacks of brown fluff, but when there's possible food they perk up and pay attention. It's funny how long their necks can be when stretched up! The chicks don't seem able to hold their heads up for very long yet. As we all know, however, food is a powerful motivator.
The parent also demonstrates what I think of as an about-to-regurgitate movements. It sort of reminds me of the cats' convulsions right before they hork up a hairball, only not as fast or violent. The parent cormorant stands up and sort of undulates front to back a few times, then bows low. This gets the chicks' attention and they start looking alert and expectant. The parent might go through the whole routine a few times before leaning towards the chick. The chick begins poking at the parent's bill, which seems to stimulate the actual regurgitation. Nom nom nom!
What I want to showcase this time is a series of photos showing a feeding session. The whole thing took about five seconds.
Look at those stubby little wings! These youngsters have some growing to do and have to make real feathers before they can fledge. Maybe they'll have done so by the time I finish up with school for the year.
One of the things that I've been doing with my Ecology class since almost the very beginning is LiMPETS monitoring in the rocky intertidal. Usually we have a classroom training session before meeting in the field to do the actual work. This year we are teaching the class in a hybrid mode, with lecture material being delivered remotely, so we don't have class meetings except for our field trips. The LiMPETS coordinator for the Monterey Bay region, Hannah, and I arranged to meet at our sampling site, where she would do a training session on the beach before we herded everyone out into the intertidal. It truly was a great plan! But the weather intervened and a spring storm blew through, bringing in a big swell. There was a high surf warning for our area the day of our scheduled LiMPETS work. Hannah and I conferred via email and decided that we'd still give it a shot, and at least the students would have an opportunity to learn about the LiMPETS program and practice with the datasheets and gear.
I arrived early to see how the surf was looking, and it was impressive. The waves were regularly covering our sampling location with whitewash, even as the tide was going out. When my co-instructor arrived and I showed him where the transect would lie, it was an easy decision to make to cancel the monitoring. But we would still be able to do the practice stuff, so we convened with Hannah on the bluff and she went into teacher mode.
We didn't bother with the transect, but had groups of students work through some quadrats out on the intertidal bench, which you can just see in the background of the photo above. Hannah kept everyone out of the danger zone and we stressed the importance of having one member of each group keep an eye on the ocean at all times. We stayed mostly in the high zone, venturing down into the upper mid zone only when the tide was at its lowest. Even then, the big swells would surge up the channels and splash up onto the benches. Nobody got swept off, though, or even more than a teensy bit damp.
Most of the students left after what little work we had for them to do, and that gave me the freedom to poke around on my own and take pictures. I hadn't had a chance to do this in a long time, and intended to make the most of a decent low tide that was almost wiped out by huge swell.
So here we go!
First up, the high-intertidal seaweeds:
And here's a typical high intertidal community at Davenport Landing. Inhabitants include:
Several large clumps of rockweed (Silvetia compressa and Fucus distichus)
Several smaller bunches of tufty reds (Endocladia muricata)
Mussels (Mytilus californianus)
Many blotches of "tar spot alga" which is the encrusting tetrasporophyte phase of Mastocarpus papillatus
The water was pretty murky, so not great for underwater photography. Some of the shots turned out pretty well, though. The soft pale purple structures that you see in the photo below are papullae, used for gas exchange. You can see these only when the star is immersed.
The anemones were, as always, happy to be photographed. In this shot, the anemone was being photobombed by a turban snail.
Here's another typical intertidal assemblage:
A couple of students stayed after the rest of the class had left. They were happy to see the nice fat ochre stars, and so many of them in one small area.
It's always good to see so many big ochre stars. For this species, in the intertidal areas that I visit, sea star wasting syndrome (SSWS) no longer seems to be a problem. Fingers crossed! We'll have to see what unfolds in the next months and years.
This week was my spring break, and although I have more than enough work to catch up on, I decided that each day I would spend a few hours doing something fun before or after getting stuck in with adult responsibilities. I didn't set up formal plans, but knew I wanted to collect a plankton sample early in the week. Monday 21 March 2022 was the vernal equinox, which seemed as good a time as any to see what was going on in the plankton.
And the plankton was quite lively! I was very pleased to see a lot of diatoms in the sample. Diatoms are early season bloomers, able to take advantage of nutrient inputs due to coastal upwelling. They are usually the most abundant phytoplankters from about March through July.
All of those button-like round objects are centric diatoms in the genus Coscinodiscus. They can be large cells, getting up to 500 μm in diameter. Coscinodiscus is in some ways the quintessential centric diatom, as you will see below.
Take a look at these objects:
Clearly, one is a circle and one is a rectangle, right? Well, yes, but these two objects are the same type of thing—they are both cells of Coscinodiscus. The easiest way to understand diatom anatomy is to think of the frustule (the outer skeleton of the cell) of Coscinodiscus as being constructed like a petri dish. Because that's actually what it is: an outer casing of silica with two halves, one of which fits over the other exactly the way a petri dish lid fits over the bottom of the petri dish. If you place a petri dish on a table and look down on it, you will see a circle. But if you pick up the petri dish and look at it from a side view, you will see a rectangle. If you don't believe me, go ahead and try it with any canned food item in your pantry. Coscinodiscus is the same. If it lands on the microscope slide lying flat, it will look like a circle; this is called the valve view because you are looking down on the surface of one of the two valves of the frustule. Most of time when we see Coscinodiscus we see it in valve view. Sometimes you get lucky and a cell remains "standing up" even after you drop a cover slip on top of your sample, and you see the cell as a rectangle. This is called the girdle view. So in the photo above, what you see on the left is a Coscinodiscus cell in valve view, and what you see on the right is the same type of cell in girdle view. Same object, two perspectives, and two shapes. By the way, this is the answer to the question posed in the previous post.
And this is what a valve view of Coscinodiscus looks like when you zoom in:
You can see some of the sculpturing on the frustule, and the beautiful golden-brown color of diatoms. The diatoms are related to the brown algae and share the same overall set of photosynthetic pigments, which explains why diatoms are often the same colors as kelps.
Another of the common diatoms around here are those in the genus Chaetoceros. The prefix 'chaet-' means 'bristle', and the cells of Chaetoceros have long bristles. Unlike Coscinodiscus, Chaetoceros forms chains. Some species form straight chains, others form spiraling chains, and still others form a sort of meandering chain that is embedded in a tiny blob of mucilage. The cells below are forming a straight chain.
In addition to all of the diatoms, there were more dinoflagellates than I expected to see. Ceratium was very well represented, often in chains of two cells.
I was even able to capture some video of Ceratium cells swimming in the thin film of water under the coverslip. Dinoflagellates have two flagella: one wrapped in that groove, or "waistline", and one that trails free. Usually it's the trailing flagellum that's easier to see, and if you watch you'll be able to see it in each of the cells.
Protoperidinium was another common dinoflagellate in the sample. Unlike the diatoms and photoautotrophic dinoflagellates, which have that sort of golden-brown color, Protoperidinium is a heterotroph. It eats other unicellular protists by extruding its cytoplasm out of the holes in its cellulose skeletal plates and engulfing prey, similar to the way an amoeba feeds. Because it does not rely on photosynthesis for obtaining fixed carbon, Protoperidinium comes in colors that we typically don't associate with photoautotrophs. Pink, red, and grayish brown are common colors. This time I saw several that were bright red.
So that's a glimpse of springtime in the ocean. Now let's look up!
Legend has it that the swallows return to San Juan Capistrano every year on March 19, which is St. Joseph's day. I don't pay attention to St. Joseph's day, but I do pay attention to the vernal equinox every year and keep an eye out for the return of our swallows to the marine lab. We get both cliff swallows (Petrochelidon pyrrhonota) and barn swallows (Hirundo rustica) building mud nests on our buildings. Last year (2021) the cliff swallows showed up first, with the barn swallows arriving a few weeks later; I remember being worried that they might not show up at all.
This year the swallows returned right on schedule. I saw my first barn swallows on the day of the vernal equinox, 21 March 2022.
They are so pretty! I haven't seen any nest-building yet, but did witness what might have been a territorial spat. The bird in the photo above is the one on the left that is retreating in the photo below
Look at that gorgeous outspread tail! Barn swallows migrate to North America from southern Mexico and Central America. The cliff swallows come all the way from South America; no wonder they're a little late arriving in California! I think they'll show up any day now, and both they and the barn swallows will begin daubing mud above doorways and under the eaves.
Somehow, no matter what else is going on and what the calendar says, it never feels like spring until the swallows are zooming around again. Spring is my favorite season, as there's so much going on, and I begin to feel energized again with the longer days. I have a busy spring teaching schedule and don't know how much time I'll have to do fun things like look at plankton for the hell of it, but will try to slow down often enough to take note of what's happening around me.
For the second year in a row (that I am aware of, anyway), the Brandt's cormorants (Urile penicillatus) have claimed the last remaining arch at Natural Bridges as a breeding rookery. I remember being so excited at "discovering" them in 2021. Anyway, they're back again, building piles of algae into nests.
BTW, if you're keeping score at home, the genus name for the North Pacific cormorants has been changed from Phalacrocorax to Urile. A 2014 study showed this North Pacific group to be a sister clade to those in the genus Phalacrocorax, and in 2021 the International Ornithologists' Union formally adopted the genus Urile for them.
During the breeding season the Brandt's cormorants develop long, wispy white plumes on the cheeks and in two smaller tufts over the shoulder blades. In my head I've been calling them Einstein plumes because although they probably do have a real name, I don't know what it is. When you see a face portrait of one of these birds, you'll know what I mean.
The color blue also features in the breeding phenotype of Brandt's cormorants. Cormorants are related to pelicans, which of course have that huge gular pouch that can hold gallons of water. The gular pouch of cormorants isn't nearly as large. For the Brandt's cormorants, the blue gular pouch indicates sexual maturity. And can you see the color of the eye of the bird that is bowing? The eye of a sexually mature bird turns a brilliant cobalt blue during the breeding season. Brandt's cormorants nest on rocks or cliffs, with the male gathering most of the nesting material. At Natural Bridges, the nests are made up mostly of algae, but I've seen a few birds flying by with surfgrass in their mouths. This male above has brought back a nice clump of red algae (a species of Cryptopleura, maybe?) to an appreciative mate.
So those are the Brandt's cormorants.
This year there is a second species of cormorant hanging out on the sides of the rock. These are pelagic cormorants (Urile pelagicus).
I first noticed the pelagic cormorants early in March. I saw those white patches on the flanks and thought, "But that's not the right body shape for a pigeon guillemot!" I came home, looked them up, and sure enough, they are pelagic cormorants. The pelagic is a little smaller and more slender than the Brandt's, and has a red face and glossy black-green plumage with the white rump patches during the breeding season. These three pelagic cormorants are on small ledges on the side of the same rock where the Brandt's cormorants are nesting, providing a nice demonstration of resource partitioning.
So, are these pelagic cormorants really the new kids on the rock? Going by my photographs from 2021, I'd say yes. I looked back through the photos I took when I discovered the Brandt's cormorants, and did not see pelagic cormorants in any of them. Of course, absence of evidence is not necessarily evidence of absence, and it could very well be that the pelagics have been there all along with the Brandt's and I simply never noticed them. Given that my area of expertise is absolutely not birds, I'm quite prepared to learn that I am wrong about this. But the pelagic cormorants are new to me, and that's reason enough to be delighted by them.
Date/time: Saturday 2022-02-19, 08:00-09:30 Location: Natural Bridges State Park Weather: Chilly (8.3C), as sun hadn't yet risen above the roofs of the houses nearby; very light breeze
For Day 2 of the 2022 Great Backyard Bird Count (GBBC) I went to Natural Bridges, not suspecting that I would be able to ID and count so many species literally just inside the park boundaries. I ended up dividing my observation period into three locations and spent about half an hour at each.
Observation spot #1: Just inside the park boundary on Delaware Avenue (see map below)
This weekend, 18-21 February 2022, are the four days of the Great Background Bird Count. This is a global community science project in which people go out and document bird life. The beauty of a project like this is that is available to anyone who has a window to the outside. Of course, anybody can look at birds any time. To participate in the official project, people need to add their observations to eBird, which is similar to iNaturalist only specific to birds.
Date/time: Friday 2022-02-18, 09:00-10:00 Location: Younger Lagoon overlook Weather: Sunny, with very slight overcast; no breeze at first, but light breeze after about 09:30
Canada goose (Branta canadensis): 6
Mallard (Anas platyrhynchos): 4 female, 4 male
Bufflehead (Bucephala albeola): 4 female
American wigeon (Mareca americana): 4 female, 5 male
American coot (Fulica americana): 12
Northern harrier (Circus hudsonius): 1
Red-tailed hawk (Buteo jamaicensis): 1
Red-winged blackbird (Agelaius phoeniceus): hard to say, but at least 20 lekking away in the field across the lagoon
Osprey (Pandion haliaetus), carrying a fish!: 1
European starling (Sturnus vulgaris): murmuration of ~100
Bewick's wren (Thryomanes bewickii): 1
Song sparrow (Melospiza melodia): 2
Yellow-rumped warbler (Setophaga coronata): 2 male
In addition to this tally of species, which is fine in and of itself but not all that interesting, I did get to see some interactions. The northern harrier is a perennial resident, and I often see it either perched on a fence post across the lagoon or soaring low over the fields. Today the red-tailed hawk was perched on a fence post, and I didn't see the harrier until it flew in several minutes later. The harrier crossed in front of the hawk, flying low, and flushed out a murmuration of starlings. It chased the starlings around for a little while, obviously not hunting them. And as much as I wish starlings hadn't been introduced to North America, the flow of a murmuration is fascinating to watch. Even a small one of about 100 birds is rather impressive. Anyway, the hawk on the fence post watched all this activity for a few minutes and seemed to be rather peeved by all the kerfuffle. It ruffled its feathers and flew off. The harrier flew away later, and the starlings kept up their murmuration until I left.
At ~05:00h UTC on 15 January 2022, the Hunga Tonga Hunga Ha'apai undersea volcano erupted. The eruption was probably followed by a massive undersea landslide, which set tsunami waves out across the Pacific Ocean. This time translates to ~21:00h PST on Friday 14 January, and for the rest of this entry all times and dates will be reported in California time. The eruption and landslide happened in the early morning in Tonga, which was the previous evening here in California.
I woke up on Saturday 15 January (yesterday, as I write this on the 16th) to reports of tsunami warnings for the entire Pacific coast of North America. The first waves were expected to hit the Monterey Bay area around 07:30h. Knowing that we are in spring tides now and that the low low tide (LLT) would be at 15:35h, I back-calculated the preceding high tide (the high high tide, or HHT, for the day) to be around 08:30h. Hmm. High tide plus tsunami surge could equal interesting things to see! And yes, as we were warned not to go down to the ocean, I planned to remain above it all and observe from the bluffs.
What the instruments measured
The volcano erupted first, and caused the landslide. When the massive displacement of water occurred in the ocean, it sent pressure waves through both the ocean and the atmosphere. But before that, the volcanic explosion itself created a pressure wave in the atmosphere. And it happens that the barometer in our weather station caught the pressure anomaly! At 04:04h on 15 January, about seven hours after the eruption, the weather station measured a spike in atmospheric pressure (circled in red in the bottom panel). Our weather station records pressure only every five minutes, so the actual spike may be a bit higher than what was recorded.
The National Oceanographic and Atmospheric Administration (NOAA) has tsunami stations established on the entire coast of the U.S., as well as earthquake monitoring stations elsewhere along the Pacific ring of fire. The tsunami station at Monterey measured sea level anomalies due to the tsunami waves striking the coast, starting at about 07:00h, as seen below.
This kind of chart is a little different from what you're probably used to, so let me explain what it shows. You have time and date along the X-axis. The blue line, which is hard to see because it is mostly obscured by the red line, is the predicted sea level; note that it follows the usual trajectory for the tides we have in this area, with two high tides and two low tides every day. The jagged red line is the interesting part. It shows the anomalies, or how the actual sea level deviates from the predicted sea level. There are both positive and negative anomalies. These anomalies are the tsunami surges that hit the monitoring buoy. Positive anomalies are the pressure waves striking the buoy (i.e., the crests of the wave), and negative anomalies are the pauses between surges, or the troughs of the wave. The first large anomaly was about 0.7 meters above the predicted sea level.
Imagine tossing a pebble into a calm pond. When the rock hits the water it sets up a series of pressure waves that emanate in all directions from the point of impact. If you watch those waves, or ripples, you notice that over time they diminish in size until eventually you don't see them anymore.
A tsunami is a similar phenomenon, only ginormously magnified. The underwater landslide displaces a huge amount of water, which then surges away in all directions. These tsunamis travel across thousands of kilometers of open ocean, where they may not make much difference in sea level. But as they approach land they behave like other waves do: they slow down and get taller. When they hit the continental shelf, they surge up coastal waterways and flood any low-lying land they encounter.
And there isn't only one surge. As you can see in the NOAA chart, surges and relaxations occurred throughout the entire day. The purple line indicates the same anomalies as the red line, only they are shown on a single horizontal line instead of on the wave of the blue line. This makes it easier to see how the magnitude of the deviations decreases over time.
What I saw
Double-checking the NOAA tide chart for Santa Cruz, I saw that the HHT would be +1.7 meters at 07:59h. I managed to get myself down to the marine lab, do my chores, and scurry out to Younger Lagoon at about 08:45h. Don't worry, I didn't have time to go down onto the beach, but watched events from the bluff, where I had a better view anyway. Remember, we had a high tide coinciding with the oncoming tsunami surge, so the potential was there for something interesting to happen. Now, a +1.7 meter (= 5.5 feet) isn't an extremely high tide. But combined with a tsunami surge, maybe that would be enough to flow over the sand berm into the lagoon.
And that's what happened. From my position on the bluff I recorded this video:
And here's my nature journal entry:
Things were pretty exciting at the Santa Cruz Small Craft Harbor, too. All day, people were recording the tsunami surges as they rushed up the harbor from Monterey Bay. Unlike the tsunami in 2011, which tore up both docks and boats, causing extensive damage, yesterday's tsunami was quite mild. I had already made plans for the day and didn't get down to the harbor to check out the action until late in the afternoon. My friend, Murray, built a little boat, Scherzo, who lives in the upper harbor. Scherzo didn't exist in 2011 so we don't know how she would have weathered things. She was floating happily when we went to see her yesterday, although she did seem to be sitting rather low in the water. She probably took on water over her transom during the biggest tsunami surges.
Scherzo is the sleek little craft on the near side of this dock. She is blue with a white cover.
The harbor patrol had blocked access to the docks so they could inspect them for structural damage. I assume, but don't know for sure, that slip renters were able to check on their boats today.
We were at the harbor at 16:30h yesterday. Sea level was still noticeably rising and falling, and even a minute of watching was rewarded with fairly drastic changes. Since we were not allowed onto the docks I was unable to record good footage of how quickly water was moving in the main channel. However, in the side channel where Scherzo is tied up we could watch the water drain. In this video, keep an eye on that rock that looks like a shark fin, near the middle of the frame.
What other people saw
In one of those inevitable consequences of any public safety announcement, the effect of a tsunami warning is to attract people to the beach. I know that many surfers headed out to surf the tsunami, and a lot of people recorded the tsunami from bridges and other places. Here are just a few of the YouTube videos showing the tsunami in the Santa Cruz area.
Video #1: Drone footage of the tsunami pushing into the mouth of the harbor and up the main channel. You can clearly see the green water from Monterey Bay pushing its way through the muddier water of the harbor itself. And the poor dredge sure did take a beating!
Video #2: Tsunami waves heading up Soquel Creek, which opens to Monterey Bay
Video #3: Cars floating at the upper harbor parking lot. I think a lot of this water came up through the storm drains, rather than flowing from the harbor onto the sidewalk and roadway.
Video #4: This video was shot from the Murray Street bridge, looking south at the lower harbor.
Video #5: This footage was shot at the upper harbor, near the dock where Scherzo lives.
So yeah, things were pretty exciting here. But the important thing to remember is that what was a source of entertainment and mild concern here in California, caused tremendous damage in Tonga and neighboring islands. Volcanic ash is settling over the island to the depth of several centimeters, fouling fresh water supplies. The ash is also clouding the air and darkening the sky. Communications have been disrupted, and it is unknown how many casualties resulted from the eruption and ensuing tsunami. Australia and New Zealand have begun deploying aircraft to assess the damage, but it will be a while before we know how bad things really are. Drinking water does seem to be the most pressing need for Tongans and inhabitants of other affected islands.
I imagine that in the coming days there will be opportunities for us to help those who need it. If you can contribute, please do so.
On this winter solstice, as we anticipate the return of light, I thought I'd write about a different kind of light.
Merriam-Webster defines fluorescence as "luminescence that is caused by the absorption of radiation at one wavelength followed by nearly immediate reradiation usually at a different wavelength and that ceases almost at once when the incident radiation stops". It is a type of luminescence that occurs in both biological and non-biological objects. For example, mushrooms and scorpions are notably fluorescent, as are several minerals. Technically, to qualify as "fluorescent" an object can absorb any wavelength of radiation and re-radiate any other, although the re-radiated wavelength is usually longer than the absorbed wavelength.
We humans, with our three (and occasionally four) color photoreceptor types, can see only the tiny fraction of the electromagnetic spectrum that we call visible light. The visible light range (approximately 400-700nm) is bounded by UV on the short end and infrared on the long end. Other organisms have very different light perception capabilities. We know, for example, that insects can see in UV and pit vipers can see in infrared. And as for mantis shrimps, which have as many as 12 types of photoreceptors, we don't yet understand how they see the world, but you can bet it's nothing like the way we do. For practical purposes, fluorescence is most easily seen when an object absorbs UV light and re-radiates light of a longer wavelength that falls into the visible light range.
When you shine a UV light on one of these fluorescent objects, you see an apparent color change from whatever it looked like under visible light. This color change is most striking in the dark, because the fluorescent object will appear to glow. The same thing happens in daylight, but is obviously more difficult to see.
Here, let me show you. A few weeks ago I went to Natural Bridges to photograph the anemones, first under normal daylight conditions and then under UV light. I have a pretty wimpy UV flashlight, it turns out, but you can still see the fluorescence.
Here's Anemone #1, under daylight:
And here's Anemone #1 under UV light:
Striking difference, isn't it?
This is Anemone #2. It was getting dark by then, but this photo was also taken without flash and I did not increase exposure of the image.
And, under UV light:
Here's what's going on. Pigment molecules in the anemones' tissues are absorbing the UV radiation and re-radiating light in the visible range. It's easier to see the fluorescence in Anemone #2 because it was much darker when I took that set of photos. Fluorescence still occurs during the day, but we can't see it as well in the daylight. This is why our local bowling alley does their Atomic Bowling at night! They can dim the overhead lights, crank up the black lights, and let the tunes roll.
Incidentally, if you've ever wondered why so-called black lights are purple, there's a reason for it. A true black light emits only UV light. UV light is invisible to us, hence the term "black", as in pure darkness. UV lights that ordinary folks like us can buy are tinged purple so that we can see it. The purple isn't UV, of course, but seeing the purple light keeps people from looking into the beam and frying their retinas from the actual UV radiation.
Sea anemones, of course, do not celebrate the solstice, but they do perceive it. They, and just about every other living thing, can sense the cyclical changes in day length as the year progresses. After tonight the days will start getting longer as we move through winter and towards spring. Personally, I cannot wait until we get the early morning low tides in the spring.
Yesterday I had some time to kill before getting a COVID test, and, as usual, wandered down to the ocean. This time I was at Seacliff State Beach. It was pretty crowded, so I walked onto the pier to see if the fishermen were having any luck. They weren't, really. One man kept catching jack silversides (Atherinopsis californiensis) that were too small to keep. There was a lot of banter about sharks and bait and crabs, but what I witnessed yesterday confirms my hypothesis that a lot of what people call "fishing" is merely an excuse to get outside for a few hours. And there is absolutely nothing wrong with that.
As for me, I have nowhere near enough patience to make a decent fisherman. I did, however keep myself amused by eavesdropping on their conversations and writing snippets in my nature journal. I did also find myself mesmerized by the anchovies. Watch for yourself.
Like sardines, anchovies are planktivorous filter feeders. If you watch the video again and can focus on an individual fish for a while, you'll see that as it swims forward, the front end becomes white and bulbous for a few seconds. That's sunlight reflecting off the fish's jaws. Anchovies have metallic silver coloring, which is a defense against predators. For fish that live in surface waters that are brightly lit, all of those glinting flashes of light make it difficult for a predator to zero in on a single fish to pursue. There is safety in numbers, and for anchovies the silvery coloring combined with schooling behavior means that if a predator manages to catch some of the fish in the baitball, most will avoid being eaten. This works against predators such as larger fish, squid, and birds, which generally capture one or a few fish at a time. But if the predator happens to be a humpback whale, which is capable of engulfing the entire school, then the anchovies are SOL. Think about it, though. For any anchovy, the probability of encountering a larger fish, squid, or bird is much higher than encountering a humpback or blue whale. Thus the selective advantage of schooling!
Okay, now back to the feeding. Anchovies have really long jaws for their size and can, like snakes, open their mouths very wide. This allows them to filter as much water as possible as they swim. Food, mostly plankton, is caught on the gill rakers, which are bony or cartilaginous structures projecting forward (i.e., towards the mouth) from the gill arches. Some fishes' gill rakers are nothing more than short nubs. Filter feeding fishes such as anchovies have long thin gill rakers. Water enters the mouth as the fish swims forward, and plankton is caught on the array of gill rakers. The water then passes over the gill filaments, where respiratory exchange occurs, and then out from underneath the operculum. Anchovies cannot suck water into their mouths, and thus can feed only while swimming forward, or ramming water into the mouth. This is a type of feeding called ram feeding.
These anchovies were very close to shore. They were feeding, so obviously there was plankton in the water. I haven't done a plankton tow in a while, as I generally assume that fall/winter plankton isn't as interesting as spring/summer plankton. However, given the presence of feeding anchovies inshore, it might be time to test that assumption.