Fish in the Bay – April 2022, Part 1: Traditional Baby Fish Month?

Long-time readers will know that April is “Baby Fish Month” in Lower South SF Bay.  Larvae of gobies and a few other fish types tend to show up in great numbers each April.  And indeed, that is what we found.  This was also the start of the winter-to-warm-season transition: Wintertime Anchovies and Longfin Smelt had largely fled the area as temperatures rose from the 12s and 13s in March to the 17s and 18s by early April.

  • La Nina fishes: Baby English Sole showed up in fair numbers (314), however, the count of young Staghorn Sculpin was a bit disappointing (92), and Pacific Herring were complete no-shows.
  • Good News: baby Crangon shrimp have fully returned after several months of near absence! (2103).
  • And, we spotted seven (7) Sturgeon on sonar. Clearly, the Sturgeon have moved in to feast on the springtime buffet.


Spawning Anchovies?  We found a few Anchovies with either eggs or milt at Pond A21 and LSB stations.  This was a huge surprise.  Since 2020, we have documented spawning Anchovies from roughly June through November.  We did not expect to see them on the springtime side of the year.  Interestingly, Anchovies off the California Coast in the cold blue Pacific spawn from late winter through spring.  Are these spawning-ready fish just stragglers that came in from the ocean?  Or, is the annual Anchovy spawning season in the Bay much longer than we realized?

Bad Clams and Snails.  More good news!  Non-native Corbula Clams and Philine sea slugs are still practically absent.  We also found no Atlantic Oyster Drills.  I am certain all three will return, but these low numbers are very encouraging.

Pink Circles.  In past reports, we identified any discovery of spawning-ready Longfin Smelt and Northern Anchovies with a pink circle around the catch number at that station.  We have decided to expand that system to all species as much as possible. (It’s easy to do, so why not?)  By expanding this system, we can see that various gobies, Topsmelt, Bay Pipefish, and Harris Mud Crabs are now in their spawning/brooding season.


Baby Fish Month?  721 baby fish showed up again this April. (Technically these babies are “post-larval” or “young juvenile,” and they are overwhelmingly Gobies) This result was a little disappointing.  We were hoping for well over 1,000.  But, it was a decent count compared to previous years.  These tiny gobies and larval fishes measure around 20mm or less so the count is very inexact.  Many slip through the net or wriggle unseen in the tray.  


1. Sharks and Rays.

Baby Leopard Shark at LSB1

Leopard Shark.  Of the three Leopards caught in April, two were tiny newborns less than 8 inches long.  The larger one was a youngster at a little over 16 inches (400 mm).   


Bat Ray at LSB1

Bat Rays.  9 Bat Rays were caught and released.  The two measured at LSB1 were young adults with wingspans around 20 inches.  The seven at LSB2 were smaller.  So far, the Bat Ray count for 2022 is a little low, but numbers should pick up with the warm season.


Guitarfish at LSB2

I will say more about this Guitarfish in a supplemental report.


2. Some of the Rare Oddballs.

Plainfin Midshipman at Coy4.

Plainfin Midshipman.  An adult Midshipman!  This “Singing Toadfish” is one of our favorites.  … more to follow.


Diamond Turbot.  We see a Diamond Turbot no more than once or twice per year.  They spawn in bays and estuaries from Humboldt County down to Baja California and feed on worms, mollusks, shrimp, and similar bugs.  We seem to be finding bigger ones as the years progress.

California Tonguefish.  This is the oddest of the oddballs and the only Tonguefish we have seen since June of 2020.  They are just a tongue-shaped body with a pair of eyes.  Like California Halibut, Tonguefish flourish here in warm El Nino years.  La Nina years do not favor them.  Birds like Pidgeon Guillemots eat them.  A lot of bigger fishes probably eat them too.


3. English Sole and Surfperch.

English Sole and a small California Halibut (top left) at LSB1.

English Sole.  316 young English Sole in April.  This was a respectable catch but smaller than expected given the strong La Nina upwelling.  Either the English Sole spawn off the coast was not as robust as hoped or some bigger fishes and birds are eating these young fishes.


Shiner Surfperch.  Only six (6) Shiners were seen.  All of them were collected at LSB stations.  These used to be among the most numerous fishes caught by anglers in Lower South SF Bay.  It is still unknown whether this is a hardy trash fish that persisted when water quality was not so good, or a desirable native that has been pushed out as a result of some other unknown factors.  Either explanation is possible.   


4. Pelagic fishes that spawn here: Anchovies, Longfin Smelt, & Topsmelt.

Spawning-ready Anchovies!  We only caught 29 Anchovies in April.  This was a sharp drop from the 1,000 to nearly 3,000 caught each month from December to March, but not atypical.  April is usually a ‘low Anchovy’ month here.  But, Anchovies with eggs or milt in April is, so far, unprecedented.  We found two Anchovies with eggs and one with milt at LSB-2 – not all were checked.  Another four out of six Anchovies in Pond A21 had eggs.  

Anchovy eggs and milt were completely unexpected. Northern Anchovies spawn off the coast at this time of year.  Until now, we have only observed in-Bay spawning readiness in summer through fall.


Longfin Smelt.  Seven (7) Longfins were caught in April.  This was also a sharp decline from March, when 539 were caught, and the typical seasonal transition.  We saw an incredible number of spawning-ready Longfins from December ‘21 through March ’22, but now the season is over.  At this point, we can only hope that the young have recruited well enough to boost numbers even higher next year.

Topsmelt.  Only four (4) Topsmelt were caught.  But as always, these smallish surface dwellers are usually missed by our deep trawling net. Three of the four Topsmelt were milting males.  Topsmelt are spawning!


5. Gobies

Staghorn Sculpin, English Sole, and skinny Yellowfin Gobies at Alv3

Yellowfin Goby adults, 28 netted this month, all looked long and skinny.  They may be a combination of spawned out females and starving males.  Adult males tend fertilized eggs in mating burrows for weeks without feeding until the eggs hatch.  At this point in the reproductive cycle, both sexes should look rather emaciated. We presume that most of the tiny ‘Unidentified Gobies” of April are young Yellowfins.

Shimofuri Gobies and Arrow/Cheekspot Gobies were still bearing eggs. Spawning for these species seems to extend over much of the warm season.  This may be why they continue to survive and thrive alongside the larger Yellowfins.

Bay Goby.  We only caught one (1) Bay Goby in April.  Unfortunately, this native continues to be a rare oddball.  Bay Gobies are difficult to distinguish from the hundreds of other types of young gobies this time of year.  


Male Chameleon Goby at LSB2

Chameleon Gobies and Shimofuri Gobies are close cousins within the Tridentiger genus.  They look similar unless you examine them closely. 

  • Chameleon males turn almost black when they are attracting females or guarding eggs.
  • Males also show bright orange ‘epaulets’ at the base of each pectoral fin. It is not known whether females show such bright coloration.  

Shimofuri Goby males also get darker during mating season, but Shimos only darken to dark brown.

  • The “epaulets” on Shimofuris turn bright white. (Yes, the epaulet color-scheme is opposite that of anal fins which are orange for Shimos and predominantly white for Chameleons.  Go figure!)
  • As pointed out before, Shimofuris have many spots under the jaw. Chameleons have no spots there.


6. Pipefish.  

Pregnant male Pipefish at Coy4.

Bay Pipefish.  We caught 42 Pipefish in April.  That is now our monthly record from 10 years of trawling.  Many of the male pipefish were visibly pregnant with eggs.  Unlike most of the other fishes in the Bay, these male pipefish tend fertile eggs in their pouch with a rudimentary placental-like system.  When the pipefish fry are ready, the belly pouch will split open at the seam, and the babies will spill out.


Pipefish at Art2 – We caught a lot of Pipefish in Artesian Slough!


7. Bugs!

Tiny Crangon in Dump Slough, 2 April 2022.

Crangon franciscorum.  Over 2100 Crangon shrimp were counted.  That is a very respectable number for an April.  All were tiny, and the majority, 1400 of them, were at upstream stations.  This is both a great relief and a big surprise.  There were very few adult Crangon through the winter brooding season.  How did these baby Crangon get here?  Will they recruit well during this second La Nina drought year? … Stay tuned! 


Harris Mud Crab.  We go long periods without seeing a Harris Mud Crab, then this month we caught 17 of them, and many were gravid.

Non-native Harris Mud Crabs were the most common invertebrate caught in trawls in the 1980s.  They have been fairly rare ever since.  They are not particularly harmful.  They are opportunists that tend to flourish when the natural ecosystem is weak.  (As a general rule, all crabs show up in abundance after death or disturbance. – Crabs eat dead stuff.)      


8. Big Fishes.

Striped Bass in Pond A19.

Striped Bass.  We caught 17 Bass in April.  The numbers are a little low, and that is good.  They are the popular game fish here, and for decades a large striped bass population was considered attainment of a water quality beneficial use for this aquatic ecosystem.  And, it is true that the presence of a large population of predatory fishes is a good sign of environmental robustness.  But, Striped Bass are the wrong fish!  


White Sturgeon.  Seven Sturgeon were seen on sonar!  These sloughs are a Sturgeon feeding ground. Sturgeon are the right fish! 


9. Misc.

Harbor Seals at Coy4.  At least eight (8) pups have arrived – supplemental report to follow.


American White Pelicans in Pond A19. – The crest, or horn, on their bills signifies breeding readiness, albeit they do not nest in the Bay Area.  They only rest and feed here. 

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