Fish in the Bay – January 2024 – Longfin New Year!

Our first trawls of the new year were fairly spectacular for a mid-January:

  • 731 Longfin Smelt. – This month alone beats all annual counts before 2021.  Longfins have returned!
  • 151 Herring. – The previous January record was 7 in 2014.  These were all youngsters (young-of-year.)  The Herring spawn about this time last year must have been very productive – or possibly very local?  Do Herring return to natal waters like Salmon & Steelhead?
  • 93 Starry Flounder. – We have never seen more than 21 Starries in a January. Usually, the number is closer to one or zero.
  • 42 Pacific Tomcods! – We caught one Tomcod in 2019 & none ever before that. In contrast, 28 were counted in 2022 & 21 in 2023.  Now, 42 this month!  42!!!  What the devil is going on here?
  • 7941 Crangon shrimp. – The vast majority of these shrimp were “berried” females (“berried = “laden with eggs”).  The last great Crangon Brooding Event we observed was the winter of 2018-19.


In theory, adult Crangon are intolerant of salinity below roughly 20 ppt.  Our berried females were pushing the low-salinity limit to deliver their broods of hatchlings to waters as low as 17 and even 15 ppt!   

Herring young-of-year were present at all stations except upstream Artesian Slough.


More than a third of the record Longfin catch was from restored Pond A21 alone.  I can’t say for certain that restoration allowed this Longfin miracle to happen, but it is hard to avoid that conclusion.

For this initial January report, four of the bigger wintertime spawning stories are featured:  Longfins, Starries, Staghorns, & Crangon Shrimp.


1. Longfin Smelt Staging for the Spawn.

Longfin Smelt count: 731.  If luck holds out, this will be the start of a 6th year of successful Longfin spawn.  (I am counting 2019 as the first year that Longfin sexual segregation and signs of positive recruitment were observed here.  No sign of Longfin spawning was observed prior to 2017.)

This January, we were again seeing darker, bluish “peacock males” with “long tails” (that means “belly flaps and long anal fins”) at fresher water upstream stations.  Chubby females and youngsters were congregating downstream.

Also note: The female shown in the bottom panel above was “expressing.”  She was dropping eggs without pressure. 

  • We do not perform field “egg-checks” on Longfin Smelt. All eggs and individuals are considered precious for this threatened species.


As always, male Longfins find suitable spawning sites at the upstream ends of Coyote Creek, Dump Slough, and Pond A19.  They use their long anal fins to sweep clean pieces of hard substrate, like a rock or a plant stem.  The cleaned surface is the place they want females to deposit sticky eggs.

This place now becomes a Longfin spawning ground each year!


A well-fed big bruiser male at UCoy2 – He was probably on his way to the spawning ground farther upstream.


A bevy of chubby females, growing fat with eggs – far downstream at Coy4


2. Starry Flounder rebounding?

Some of the 54 Starry Flounder that were caught far upstream at UCoy1.

Starry Flounder count: 93.  The Starry surge continues.  We first noticed hundreds of tiny baby Starries last May.  We counted almost 100 yearlings this January.  They return for the winter spawn.  These yearlings are just old enough to be reproductive themselves. 

  • Starry Flounder were once abundant like this until the 1980s.  Our baseline expectations have shifted considerably! 


3. Crangon Shrimp Brooding Event.

Some of the 1397 Crangon Shrimp counted at Coy4.  All but a few of these were gravid!

Crangon Shrimp count: 7,941.  The vast majority of Crangon were gravid females, each carrying full clutches of developing eggs.
This is the first large-scale Crangon brooding event we have observed since December – February 2018-19.  

However, there is a major caveat: 

  • We see a few berried females, carrying bright yellowish masses of eggs. almost every year around December through January.
  • Adult female Crangon do not tolerate salinity below about 20 ppt according to literature. Some amount of Crangon brooding probably occurs every winter in saltier water beyond our Lower South Bay trawling range.  


Crangon are strange creatures.  They mostly hatch as tiny males that immediately swim far upstream to brackish marshes.  Hatchlings grow quickly over several months and slowly migrate downstream to saltier Bay water.  Young males eventually mingle with previous year-groups of ready females.  Then, a year to 18 months later, young male Crangon turn into females! 

  • Crangon are protandrous hermaphrodites. Males that hatched and recruited in the marsh eventually return here as gravid females.


More gravid Crangon Shrimp at Coy2 – with two Staghorn Sculpin.

Crangon salinity tolerances seem even stranger.  Baby male Crangon desire low-salinity (less than 10 ppt?) marshes for recruitment.  But, they return later in life as mature females that do not tolerate salinity much below 20 ppt. 

  • Crangon females must release new hatchlings as close to creek mouths as they dare.
  • Crangon (male) hatchlings home in on the fresher creek mouths.
  • Tiny foods (copepods and mysids) bloom fastest near the detritus washed down from creeks!


4. Staghorn Sculpin Gravid Belly Checks.

Staghorn Sculpin count = 40.  Staghorns also hunker down to spawn in winter. January counts seem to be low due to the cryptic nature of their spawn. Males build and defend “love grotto” hollows beneath rocks and plant roots where they hope to induce females to lay eggs.    


We generally catch bigger females in the cold time of year.  If the spawn is successful, we will start seeing tiny babies by March or April.


This time of year – I tend to guess that these are gravid females.  However, Staghorns also like to stuff themselves full of Crangon Shrimp or any other available food. You can never be certain if they are gravid females or just typically gluttonous Sculpins. 

  • Science can run amok: Idle curiosity calls for a closer look inside these sculpin bellies to count the eggs.  But, would the sacrifice be worth the knowledge gained?  We can trust our eyes for this one: This is Staghorn spawning time! 


Harbor Seal count:  38(???)  Seal counts from photos are an approximation, at best. 

Calaveras Point Seal Rookery is mainly comprised of females.  During Seal-fertile months, a few unattached males usually loiter nearby.  They wait for a chance to sneak past any aggressive alpha that stands guard.  One or two males occasionally pair-off in a battle for dominance.

  • Many of these females are pregnant now.  Pups arrive around March.

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