Fish in the Bay – January 2025 Part 2. Other Bugs & Fishes.

This second part covers additional fishes and bugs that were not included in the January report.  

1. Colorful Clupeiforms. 

Wintertime abundance of Shad, Anchovies, and Herring affords us yet another opportunity to observe the miracle of Clupeiform color change. 

• In accordance with the color change rules, the Threadfin Shad shown above ‘browned-down” to a color close to that of an old copper penny where salinity was below 10 ppt.

30 Anchovies and one Herring were caught at station Alv3.  Salinity was a little higher on the surface compared to upstream stations Alv1 & Alv2.  Salinity was ~ 5 ppt higher near the bottom. 

• We surmised that bluer Anchovies may have been cruising along the bottom where Salinity was just over 19 ppt. (Water in our counting trays was collected at the surface (~14ppt), so all fishes were slowly browning down as we watched them.
• Herring are always at least a few shades browner than either Anchovies or Shad.

Baby Anchovies!  Over 350 of the 390 Anchovies netted at LSB stations were babies.  2024 was another good Anchovy spawning year.

January Anchovy count = 467.  That is a decent number for a January, albeit not as high as the recent blockbuster Anchovy years of 2021 and 2022.  Nonetheless, 2024 is off to a better-than-average Anchovy start.

 Blue fishes.  Herring, Shad, and Anchovies ‘blue-up’ when water salinity rises above roughly 19 ppt.

• Herring and Shad blue-up to a cyan/sky blue hue (“Rivulet” on the Kudela Lab/Sherwin Williams paint scale).
• Anchovies display a darker indigo shade of blue, but as always, Anchovies lose guanine in dorsal chromatophores. A trace of blue can still be seen along the lateral line in this example, but you have to look hard to see it.  

2. Gobies & Sculpin

Shimofuri Goby count = 6.  The Shimo population exploded from 2021 through 2023.  For a brief period, Shimos outnumbered all other gobies we find in Lower South Bay.  Then, just as suddenly, Shimo numbers declined after early 2024.  We have no explanation for this sudden decline.

Arrow/Cheekspot Goby count = 6.  Native Arrow and Cheekspot Gobies are always present.  Arrow Gobies spawn around March-April.  Cheekspots spawn in mid-summer.

Shokihaze Goby count = 10.  Shokihaze numbers dropped when the Shimofuri population exploded.  We saw a small rebound in Shokihazes in the second half of 2024 when Shimos became quite scarce. 

Yellowfin Goby count = 13.  Yellowfins had always outnumbered all other gobies – until Shimofuris overtook them a few years ago.  Now, Yellowfins are again back in first place.  Nonetheless, even current Yellowfin counts remain a little below our historical average.   

Spring is spawning season for both Yellowfin and Arrow Gobies.  Trawls here typically pick up one to three dozen large adult Yellowfins in each of the first few months of the year.  Then comes “Baby Fish Month” in April-May.

• At this point, larger male Yellowfins are excavating burrows in preparation for their season of love. Some males develop reddish heads – this could either be skin abrasion from digging, or perhaps it is a mating display?   Investigation continues.
• I used to despise these gobies as non-native “Cockroaches of the Bay” (Kathy Hieb, USFWS, perscom).  Over time, I have grown to accept them.

Staghorn Sculpin count = 4.  Staghorns also declined sharply after mid-2024.  This makes sense. They are a documented “La Nina fish.”  Strong El Nino conditions early last year could have, and should have, hammered them.  Hopefully, the latest La Nina flip will start bumping the numbers up.

Fish and Bug scene at Coy3

3. Bugs (Inverts).

Polyorchis count = 4. When we first spotted this creature in the tray, we thought it was a jumbo-sized Ctenophore – a ‘Comb Jelly.’  On closer look, we could see this was some kind of ‘Jelly fish,’ a member of the Cnidarian phylum.  But, we were wrong again! 

This ancient animal is Polyorchis, aka “The Red-eyed Medusa.”  Polyorchis is neither Ctenophore nor Cnidarian.  This creature is a Hydrozoan!  We have caught a few before.  This is not a common catch!

• Look closely at this animal – more than 50 tiny red eyespots are looking back at you!
• Some say, this is the most beautiful Jelly found along the California coast. https://www.aquariumofpacific.org/onlinelearningcenter/species/red_eyed_medusa 
• Possibly a fashion trend – https://www.instagram.com/fashion.biologique/p/CIVkNLwg0_u/
• A matter of opinion: I am more partial to the beauty of the Pacific Sea Nettle. https://www.aquariumofpacific.org/onlinelearningcenter/species/pacific_sea_nettle

Polyorchis: hydrozoans that look like Jellies & have many red eyes!  LSB2, 4 Jan 2025.

Corbula clam count = 1,163.  This is not good!  Corbula counts are usually lower in January.  We don’t like non-native Corbula.  Corbula are ecosystem killers.  Bigger mature clams tend to congregate in Alviso Slough and near station UCoy2.  Tiny baby Corbula show up a little farther downstream where they face a brunt of natural controls – sessile organisms like tunicates and barnacles, and predators like Philine snails and Oyster drills. 

Devil Bug count = 1.  This count is highly uncertain.  We don’t take care in counting Devil Bug/Fish Gill Parasites because they are tricky bugs.  When the fish is stressed, the bug quickly “abandons ship” and seeks a new host.  They are nasty bugs.  We don’t like them.

Crangon shrimp count = 4,537.  So far, the Crangon catch looks promising.  We saw many adult females either loaded with eggs or showing the yellowish sign of a developing egg mass.   

Crangon mamas will soon release thousands of tiny hatchlings.  The young will seek fresher water sloughs for recruitment. 

• Baby Crangon are about the size of Mysids. They are an important food source for small fishes in upstream marshes. 
• Crangon brooding events always happen in winter around December – February, but we don’t see brooding every year.  Rainwater flushing is an important component, but there seem to be other influences.

Upogebia / Mud Shrimp.  Every once in a while, we catch an oddball Mud Shrimp.  Mud Shrimp are defenseless outside the safety of their deep burrow arcades.  As far as we know, adults are incapable of digging themselves a new home.  Upogebia searching for shelter: https://www.youtube.com/watch?v=QF0mJ6vdsAw

• It’s a dangerous world for unhoused Mud Shrimp. Anglers will tell you that Mud Shrimp and Ghost Shrimp are like candy for Sturgeon.  Ghost Shrimp, close cousins of these mini-lobsters, are often sold as bait. … They all look like lobsters, ergo they probably taste like lobsters.
• Extremely beneficial ecosystem engineers! Mud Shrimp construct vast networks of tunnels under marsh vegetation.  They oxygenate the deep soil and cycle nutrients. 
• Non-native “Upogebia major” replaced native “U. pugettensis” within the last 20 years or so. An equally non-native Bopyrid Isopod parasite was the key player in this tragedy.  The full story is told here:  https://www.ogfishlab.com/2022/01/01/fish-in-the-bay-january-2021-mud-shrimp-alert-upogebia-explosion-on-new-years-day/  
• Removing Bopyrid Isopods from Upogebia is a hobby for some:  https://www.youtube.com/shorts/2k5tJYsxF2E 
• The newer “Upogebia major” is at least as beneficial as the native variety.

Iron miners of the ancient Marsh.  Organisms like Upogebia have cycled nutrients and sequestered iron, silica, and phosphorus into sediment for almost a billion years.  To a significant extent, we owe our own evolution and modern technological advancement to animals like these!

• What is Ironstone? (and how did shrimp build a bridge?) – Watch at roughly 10-minute mark.   https://www.youtube.com/watch?v=OJu40ncLPro “chewing and pooing.”
• We released this Upogebia and wished him the best of luck.

Gimme Shelter (Remastered 2019)  https://www.youtube.com/watch?v=QeglgSWKSIY