Fish in the Bay – Other Critters in South SF Bay. July/Aug 2026.

August 31, 2026 Jim Ervin
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Fieldwork, Fish in Lower South Bay, News

July/August report – All the other critters.

This is a follow-up to the “Bad Mollusk” report to cover some of the many other creatures caught in South Bay in July and August. 

This year is starting to feel like a “big one” from the perspective of our Lower South Bay (LSB) record. Corbula clams exploded, Halibut are at a 10-year high.  And most of the other fishes and bugs have declined. This all seems to coincide with the extra strong El Nino they have been predicting for months now.

Has this latest twitch of the tropical butterfly induced a tropic cascade in San Francisco Bay? 

1. Important Fishes.

Elasmobranchs.  Each of our live-bearing sharks and rays follow the same annual cycle.  Pregnant females migrate into LSB to deliver their pups. Sitting at or near the top of the food web, they serve as indicators of the strength or weakness of the entire trophic pyramid.    
 
Bat Ray totals July/Aug: Bair = 1/0.  Eden = 1/5. LSB = 0/4.  The LSB year-to-date Bat Ray total is 43.  This is the lowest we have seen since 2018 at least. 

Leopard Sharks.  Bair = 0/0.  Eden = 0/1. LSB = 0/0.  We caught only one Leopard Shark in July-August over an expanded area that includes Bair Island and Eden Landing. This is not good!

  • Leopard Sharks and Bat Rays feed on shrimp, worms, and tiny gobies. Low shrimp and goby totals in 2026 could be impacting elasmobranchs.

Guitarfish.  One baby girl Guitarfish was caught at LSB1 so far this summer.  (We never see more than a few Guitarfish each year.)      

Anchovy totals July/Aug: Bair = 250/37.  Eden = 17/0. LSB = 172/118.  – Always remember to double Bair Island and Eden Landing figures to render comparable Catch Per Unit Effort (CPUE).  *CPUE numbers are shown in red.* 

The LSB year-to-date Anchovy total is 1539 – the lowest since 2017.  This is not a crisis by any means, but it again suggests that ocean warming could be at work here.

Halibut totals July/Aug: Bair = 25/12.  Eden = 11/4. LSB = 32/23.  After doubling Bair Island numbers for CPUE, Bair comes out as the top Halibut recruitment zone. 

Year-to-date total for LSB = 361.  Halibut totals are already above almost all years after 2016.  El Nino fishes like Halibut, proliferate when coastal Sea Surface Temperatures (SSTs) are higher. 

2. Little Fishes are also important. 

Yellowfin and Arrow Gobies. (See numbers in the image above.)

The Yellowfin year-to-date total for LSB is 844.  That is on the low side, but we have had lower Yellowfin year-end numbers as recently as 2023 and 2019.  Yellowfins seem to be randomly variable.

LSB is a significant haven for Yellowfin and native Arrow Gobies.  Most likely it is because of a combination of lower salinity, shallower and warmer water, plus a more consistently soft, muddy bottom.

Cheekspot Gobies.  Cheekspots prefer slightly deeper and cooler water at higher salinity.  In LSB. Most of those we catch in Lower South Bay are from the deeper and cooler LSB and Coy4 stations.

  • In all other parts of SF Bay, Cheekspots usually outnumber similarly-sized Arrow Gobies.

Chameleon Gobies prefer near marine-level salinity.  This is well documented in literature. Chameleons are much more common where water is saltier.

Shimofuri Gobies. Shimos are slightly fresher water cousins of Chameleons.  From 2020 through 2023, we counted hundreds of non-native Shimos in LSB in late summer months. Since early 2024, Shimos rapidly disappeared.  We have only seen 20 since April 2026, and then ZERO Shimos in August.  Where did they go?

  • We suspect that Shimos in LSB are particularly sensitive to the current Corbula explosion. Until the last few years, we found the highest concentrations of Shimos at mostly the same locations in Alviso Slough and Coyote Creek that are today covered with Corbula clams. 

Bay Pipefish.  Year-to-date count in LSB = 26.  The number is a little low, but not unusual.  

  • Pipefish are straight skinny seahorses that are found in sloughs and near shores all over San Francisco Bay. 

The scene at one of the upstream stations in LSB in July.

3. Benthic Complexities at Bair Island & Eden Landing.

In countless ways, the underwater environment just a little farther north is vastly different than our more familiar ‘Lower South Bay’ home. 

At Bair Island and Eden Landing, we find creatures rarely or never seen in Lower South Bay.  Three of the critters shown here look like spindly spiders. None of them are related to terrestrial spiders or each other.  

This is mostly from Wikipedia:

  • Hilgendorf’s sea spider, scientifically known as Ammothea hilgendorfi, is a tiny marine creature native to the Pacific Ocean.  [NOT a crab!]
  • P = Pear Crab – Tuberculate Pear Crab. (Pyromaia tuberculata), also known as the fire crab.  It is a member of the superfamily majoidea, also called “spider crabs”.  https://en.wikipedia.org/wiki/Pyromaia_tuberculata
  • D = Decorator crab (Loxorhynchus crispatus), also known as the masking crab or moss crab, is a species of true crab in the family Epialtidae. It is found in the East Pacific. This crab has slightly stubbier legs and uses Velcro-like bristles on its shell to attach seaweed, algae, and live sea anemones for camouflage.  https://en.wikipedia.org/wiki/Loxorhynchus_crispatus 

Caprellids are another strange invertebrate we find farther to the north – but only very rarely in LSB. 

Shiner Surfperch at Bair Island, Cork1, 12 July.

We catch more Shiner Surfperch where Caprellids also happen to be.

  • “Caprellids are not normally considered a main source of food for fish, but when shiner perch (Cymatogaster aggregata) migrate into the eelgrass beds for reproduction, they target caprellids.”  https://en.wikipedia.org/wiki/Caprellidae

Tunicates and Worms (Polychaetes) in Lower South Bay: numbers are generally low.

  • We only ever see one kind of Tunicate, the non-native “Sea Grape,” aka Molgula manhattensis – https://en.wikipedia.org/wiki/Molgula_manhattensis.
  • Polychaetes (segmented worms) are similarly restricted to just a few species. Only three types of Polychaetes are present: the “Pile Worm,” aka Alitta Succenea, the “Long Skinny Worm” which have not yet identified to species – plus an occasional Scaleworm.

At both Bair Island and Eden Landing we have identified several additional species of both worms and tunicates, like Spaghetti Worms and colonial tunicates (Botrylloides violaceus https://en.wikipedia.org/wiki/Botrylloides_violaceus), for example.  Our identification skills for some of these new organisms are still developing.  Figuring out how to count or quantify gelatinous interconnected masses of tunicates is another problem. 

These squishy organisms are ecologically important.  –  From Google AI:

Marine tunicates serve as vital ocean purifiers and major drivers of the global carbon cycle. Though they often look like simple blobs or sponges, these incredible invertebrates perform crucial ecological services that keep marine ecosystems balanced.

Polychaetes perform essential ecological services that keep ocean floors healthy and support marine life.  Specific Services:

  • Bioturbation (Sediment Mixing): As they dig tunnels and move through sand and mud, polychaetes mix the seafloor. This action brings oxygen deeper into the sediment, preventing harmful dead zones from forming.
  • Nutrient Cycling and Decomposition: They break down dead organic matter and detritus. They turn this waste into simpler nutrients that fuel plant plankton and other marine life.
  • Food Web Support: Polychaetes serve as a rich protein source for many fish, crustaceans, and birds. They also control smaller invertebrate populations by acting as predators.
  • Bioindicators of Pollution: Certain species react strongly to water quality changes. Scientists use them to monitor pollution, as some opportunistic species thrive in disturbed areas while sensitive species disappear.

Beds of Eelgrass are another complexity we find at some locations just a little farther north. Just off the shore of Eden Landing, waving stands of Zostera become visible at low tide.  The tall grasses are extremely beneficial, so we steer clear of them.

From Google AI: Eelgrass is a marine flowering plant (Zostera species) with long, ribbon-like green leaves that form dense underwater meadows.

Ecological Importance

  • Habitat: Acts as a vital nursery, offering food and shelter to small fish, crabs, seahorses, and migratory birds.
  • Protection: Slows down wave energy, which stabilizes underwater sediment and protects shorelines from erosion.
  • Carbon Storage: Absorbs and stores large amounts of carbon dioxide in its surrounding mud and sand, acting as an important blue carbon ecosystem.
  • Water Quality: Cleans the water by absorbing excess nutrients and trapping floating particles.

4. Bonus Fish.

Our second Plainfin Midshipman caught in Lower South Bay this year:  This one appears to be a big male Type 1.  (“Big” is relative here: Midshipmen grow much bigger along the coast where they can access the deep blue sea.)

Midshipmen catch #3 in 2026:  A baby Midshipman at LSB2 on 13 Aug.

Blue October – Into the Ocean: https://www.youtube.com/watch?v=ZES3nJQYJok 

Fieldwork, Fish in Lower South Bay, News