Fish in the Bay – October 2023, Fall Begins.

Several October spoilers were given in the previous post.  Much more remains to be reported.

  • We will only cover a few important developments for now.


Longfin Smelt.  Longfins are returning for the winter spawn.

The Silverside Tsunami is subsiding. 
But, don’t be fooled.  They will be back!


Shimofuri Explosion.  Shimo numbers are also in decline after September.  Don’t be fooled.  They too, will be back!

105 Bat Rays in October!  With September and October results, we jumped from a crappy Bat Ray year to a new potential record-breaker.

Musculista (Asian Date Mussels).  This could be a serious invasion!   — To be discussed separately in another post.


1. Longfin Smelt.

Longfin Smelt count = 94.  This is the best Longfin October ever – by far!  We usually catch only zero to a few Longfins this early in the season.  The previous October record was 37 in 2021.  If our luck holds, we may achieve another record year (knock on wood).

Interesting tidbit:   UC Davis researchers have already noted that early-season Longfins tend to be young and small.  Big adults generally show up a month or two later.  What’s up with that?

There was no clear Longfin size gradient in October.  Longfins at all stations averaged between roughly 50 to 65 mm with just a few larger and smaller outliers. 

So many questions.  …

  • Do young Longfins arrive early because they don’t migrate as far out into the Bay during summer? Or, are they just young and inexperienced?
  • Will these young Longfins successfully spawn this year?
  • Will young Longfins survive to return next year?



Left: Sami measuring, photographing, & preserving Longfins for analysis.  Right: Longfins caught at UCoy2. 

Good News:  Ongoing studies continue, and every year the local Longfin population appears to be increasing. 
Stomachs, livers, gonads, and otoliths will be analyzed to track ages, health, and reproductive readiness of some of these early arrivals.  
Some fish are also now being packed in liquid N2 for additional hormone analysis that has been added to the data collection effort. 

  • We must learn the secret of this population’s success.
  • Any small environmental catastrophe, like a red tide bloom, could still wipe out years of work!


2. Bat Rays.

Bat Ray count = 105.  Another record!  This was the most Bat Rays ever caught in a single month. 

First, we caught 34 Bat Rays at Coy2. … with a tire.

Tires are always unpleasant surprises.  This tire was covered in barnacles and was full of mud and small critters.  The tire itself was an old Sears brand.  We always check for any signs of new tires in the marsh.  So far, all tires appear to be at least a few to several decades old. 

  • Nowadays, we carry tires back to Alviso Marina for disposal as deck space allows.  In the old days, we didn’t.  It did not occur to us that we would still be trawling here several years later. 
  • Catching tires sucks!  We must get rid of these tires!


34 Bat Rays in the tub after tire removal at Coy2.

All Rays were young.  Most were still babies.  It seems that Mama Bat Rays waited until late this year to deliver their pups.


Then, we caught 50 more Bat Rays at Coy3.  50 in a single trawl!  We have never seen so many Rays stuffed into a single catch.  

Volumetric Analysis:

  • The mouth of the net is 14 feet wide and sweeps a path several hundred feet long.
  • The channel bottom in Coyote Creek varies from at least 200 to 400 feet wide.
  • The distance between stations Coy2 and Coy3 is a little over a mile.
  • Add additional miles of channel length and width for stations Alv3 & Coy4 where 10 more baby Bat Rays were netted at each.
  • If we assume the net caught representative samples at each station …

There must have been a bazillion baby Bat Rays lining the Coyote Creek bottom on October 8th

With so many baby Bat Rays comes great risks and responsibilities.  The responsibility is to measure and release each Ray safely and quickly.  The risk is getting stuck by a stinger.  Bat Rays are slippery and muscular.  The stinger strike-range is limited, but any slip ups could be painful.

Pro Tips:

  1. Secure the Ray with a dip net or other handy tool.
  2. Grasp the Ray by its spiracles (the openings behind his or her eyes).
  3. Measure and check for sex.
  4. Release the Ray overboard.

Caution:  Be quick and careful.  When the spiracles are plugged, the Ray cannot breathe.  You are choking the animal.  If measurement is taking too long, loosen the grip or return the Ray to the tub so it can catch its breath.


3. Sentinel Fishes in the Marsh.

Two of three Bay Pipefish at UCoy1, 7 Oct 2023.

Bay Pipefish.  October catch = 8.  We rarely catch very many Pipefish.  They live in vegetation (and bryozoa) along the channel and pond margins.  The otter trawl collects from the mid-channel.  Once in a while, stray Pipefish fall into the net.  

The Pipefish Story:  Bay Pipefish are essentially seahorses. They have seahorse faces and tiny seahorse mouths.  Female Pipefish impregnate males by depositing eggs in the male belly pouch. We usually find pregnant males in the spring and through the warm season.  A short time after eggs hatch, the male releases tiny babies to fend for themselves.  People who raise seahorses know that the tiny babies must find especially tiny food, like rotifers and copepod nauplii, to survive.

  • Bay Pipefish indicate presence of tiny fish food in this marsh habitat.


Two alpha male Longjaw Mudsuckers at Dmp1.  Note the ‘long jawbone’ on each fish.

Longjaw Mudsucker count = 2.  The year-to-date Mudsucker count is 31.  That is low.  Annual counts by otter trawl have ranged from 21 to 135 since 2014 with no obvious trend.  This is another fish that avoids being caught out in the middle of the channel, so otter trawl catch numbers do not necessarily reflect the status of the population.

The Mudsucker story:  Mudsuckers thrive in warm shallow vegetated marshes.  Big male Mudsuckers seek defensible burrows in the mud banks amongst roots and rhizomes of marsh plants starting about this time of year.  They ward off any other males using their giant long-jawed mouths.  A successful male will seduce one or more females to deposit eggs in his burrow.  The male then fertilizes and guards the eggs until hatch.

  • Longjaw Mudsuckers indicate that healthy pickleweed & bulrush marsh is nearby.


Striped Bass count = 1 (one).  The single Striped Bass caught in October was a fairly large one (430 mm or almost 17 inches).  Unsurprisingly, it was caught in Artesian Slough where the SJSC RWF provides a steady flow of richly oxygenated water just upstream.  

  • Dissolved Oxygen (DO) was above 6 mg/l near the surface in Artesian Slough and between 4 and 5 mg/l everywhere else in nearby areas of Coyote Creek and marshes.

The Striped Bass story:  Striped Bass were first introduced to California by Dr. Livingston Stone, I believe in 1879. 

1872:  Among the issues Livingston Stone addressed were the effects of overfishing, and the need to feed a surging human population. It was decided that several marine species long-established as food staples on the East Coast — shad, striped bass, catfish, Penobscot salmon, eels, lobsters, and others — should be transplanted to the West Coast. Stone, tasked with safely transporting the fish cross-country, transformed a Central Pacific Railroad car into a 2,000-gallon aquarium on wheels, employing ice, milk cans, and a hand-aeration system.

Striped Bass (and American Shad) introduction was very successful.  Bass rapidly populated the rivers of California.  The barracuda-like hunters soon assumed near apex predator status. A commercial fishery was established within just a few years.  To this day, Striped Bass are a favorite sport fish in the rivers of California and out in the ocean.

  • The presence of Striped Bass in the warm season indicates that the DO level is probably higher than normal, and our native fishes are about to be eaten.


 4. Blackbirds.

A cloud of Blackbirds erupting from California Bulrush in Dump Slough on September 9th.

Blackbirds.  We first noticed giant flocks of Blackbirds in the newly emerged stands of California Bulrush in August. 

We have seen Blackbirds here in the past. These giant flocks usually hang out along the periphery of Newby Island Landfill where they dumpster dive and/or pick nutritious morsels from compost piles. 

As mentioned in August, these Blackbirds are a diverse mix of European Starlings, Brown-headed Cowbirds, Red-winged Blackbirds, and threatened Tricolored Blackbirds at the very least. 

Dump Slough typically supports large stands of California Bulrush, albeit the stands retreated substantially during the recent drought years. 

For some reason, the re-emergence of Bulrush habitat this year has proven powerfully attractive to many Blackbirds that largely ignored it in the past.  Is this a good thing?  Or, a bad thing?

Red-wings and Tricolors are the native marsh species. 


Bad news:  Most of these Blackbirds are non-native types.

Good news:  Both Red-winged and Tricolored Blackbirds appear to be present!

Red-winged and Tricolored identification guides:


So many stories!


Genesis – Home By The Sea

“Welcome to the Home by the Sea”

(BTW:  This is a decent Halloween theme song.) 

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