Fish in the Bay – August 2022, Bat Ray Bonanza.

A slightly belated report from August trawls.  At the time of this report, we were not yet aware of Red Tide troubles brewing in the bigger Bay to the north nor of the impending triple-digit Heat Dome that eventually arrived in early September.  Instead, we enjoyed another pleasant green-water month in Lower South Bay.  Who could have known that a potential ecological catastrophe was headed our way?


Bat Ray Celebration.

The annual Bat Ray record was broken!  We caught our 132nd Bat Rays at station Coy1 on Sunday.  2022 is now our record Bat Ray year.  Like Leopard Sharks, Bat Rays appreciate the drought year extra saltiness, but high productivity from this current double (and potentially triple) La Nina must be contributing.  

And, improving Anchovy numbers continue to indicate that restored marshes are now reliable producers of tiny food that feeds the entire system.

Bat Ray Traffic Jam – 50 out of 70 Rays were caught at Coy1 and Coy2   In July, we noted a Palaemon traffic jam at the same location.  Palaemon are still concentrated at these stations, but the Bat Rays have noticed. They are feeding on them!   


The summertime Anchovy spawn continues. 1459 Anchovies were caught in August.  High heat and low DO should be hard on these normally sea-going fishes.  To this day, I do not understand how Anchovies endure warm brackish marshes in LSB, but they do.


1. Fishes

Luca shows three Mudsuckers from Pond A21.

Luca’s note:  We caught 16 Mudsuckers this month.  Mudsuckers are very slippery to the touch.  Those that we usually catch are young females and smallish beta males who have not yet found their own breeding burrow.  We only saw one mid-sized dominant male Mudsucker (84 mm) in Dump Slough. 

Editor’s note:  Luca returned to his regular studies at California State Maritime Academy after mid-August.  We look forward to having him again join our trawls in the future.


Pregnant dad Pipefish at Art1.

Bay Pipefish.  7 Pipefish were caught in August.  2022 is our record Pipefish year: 139 so far.  (The previous record year was 2015 with 89.)

The Pipefish shown here is a male giving birth
.  In the Seahorse/Pipefish lifecycle, females impregnate males with eggs.  Males fertilize and incubate eggs in a belly pouch.  When the babies are ready, the male Pipefish’s belly pouch splits down the middle, and the fry are released. 

  • Baby Pipefish require a reliable diet of extremely tiny food like rotifers, ciliates, and copepod nauplii.


A cloud of Bat Rays at Coy2!  As we trawled station Coy2 in the main channel of Coyote Creek, we saw an odd display on the sonar screen:  Sonar indicated many mid-sized fishes under us. Some cast dark shadows to the sides.  The identity of these mystery blips was solved when we recovered the net.


Bat Rays.  Both monthly and annual Bat Ray records were broken: We caught 70 in August. That is the highest monthly total by far.  And, the August number tipped us over the annual record set just last year.  2022 is now our record Bat Ray year – see celebration below. 

27 Bat Rays were netted at Coy2 on Saturday. Another 23 were caught just upstream at Coy1 on Sunday.


Baby Girl Bat Ray at Coy3.  This is the smallest Bat Ray we have ever measured.  She almost fit in the palm of my hand!  She was certainly born within the last day or two.  After a few photos, we returned her quickly to the marsh.

Mama Bat Rays birth between 2 to 10 pups each summer.  This is a Bat Ray pupping place!


Celebration:  2022 is now our record Bat Ray year!


Anchovies!  As in previous months, Anchovies with eggs or milt were observed at all stations. 1459 Anchovies were counted in August.  The numbers have gradually dropped since June but remain very high compared to historical averages. 


2. Egg Eaters.

Topsmelt in Pond A19.

Attack of the egg eaters!  Numbers of Topsmelt, Inland Silversides, and Three-spined Sticklebacks jumped to 117, 43, and 317 respectively.  

Fortunately, these numbers are still low. All three species eat eggs and fry of spawning fishes, like Anchovies or Longfin Smelt.  It stands to reason that their numbers would increase through the warm Anchovy spawning season.   


Luca with Three-spined Sticklebacks at Pond A19.

Lucas note:  Three-spined Sticklebacks.  We have been having a Stickleback resurgence this year.  This is the most we have seen since July 2020.  We caught almost 5000 Sticklebacks in 2016!  We also had a big surge in Anchovies in 2016.  Is that the explanation?  


3. Red Algae

Luca sifts through the Ceramium red glop at LSB1.

Luca’s note:  Every August we seem to find Ceramium. Jim first sighted sprigs of it in 2017. Ceramium wasn’t as expansive as it was last year when it spread all the way down to Coy3. We don’t know exactly why Ceramium has been exploding the last few years.

• It is difficult to identify Ceramium to species:


4. Bad clams.

Corbula clams at Alv3 (One Musculista mussel shown at left.)

Bad News:  516 Corbula Clams were collected in August.  The annual count is still low – just a little over 1,200 since January.  But, any Corbula is a bad Corbula here!  They recruit in spring when the rivers flow and then grow through the warm season.  

Fortunately, Lower South Bay appears to have multiple layers of biotic protection against this non-native pest: Oyster Drills, Philine sea slugs, English Sole, Crabs, Barnacles and Tunicates, and various species of diving ducks, to name a few.

(Barnacles and Tunicates attach themselves to any hard substrate available where salinity climbs above 15 or 20 ppt. They may not outright kill surface-dwelling Corbula Clams, but they do appear to impede clam mobility and feeding.)  


5. Bryozoa to the rescue?

Mossy Bryozoan.  The net scooped up a number of Mossy Bryozoan balls in both Alviso Slough and at Upper Coyote Creek stations.  We very commonly see Mossy Bryozoan at these locations in the main stems of either Coyote Creek or Guadalupe River (Alviso Slough) near where fresh water first turns brackish. Occasionally, when we pass by at very low tides we see numerous clumps attached to any available solid roots or debris. 

Each “Bryo Ball” consists of tens of thousands of tiny filter-feeding animals, called zooids. They build these colonial structures out of chitin.  Bryo colonies appear very coral-like, and the life cycle and habits of tiny zooids are very similar to those of coral polyps, however, Bryozoa are another completely different life form.

A vast army of filter-feeding Bryozoans could be one layer of biotic defense against red tides caused by Dinoflagellates and Raphidophytes.  They may not consume Dinos and Raphidophytes directly, BUT they likely help control excess bacteria and diatoms that feed a red tide bloom.


What other creatures are helping to defend Lower South Bay against the red tide?

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