Fish in the Bay – June 2019, UC Davis Trawls – Freshness Continues

Hello folks.  I joined Jim Hobbs and the UC Davis trawling surveys on Saturday, June 1st.  It was a crazy mixed up weekend due extreme tides induced by the New Moon in combination with approaching aphelion (Earth’s farthest distance from the Sun = July 4th this year).

Trawl map on a new moon weekend.

As an extreme-tide workaround, Bay-side trawls were conducted on Sunday.  Upper Coyote Creek was trawled on Saturday.

Note: As discussed in previous posts, New Moon and Full Moon “Spring Tides” occur every month with no loss of life or limb as far as I know.  The only exceptional difficulties for trawl scheduling happen in early January and early July when the Earth passes closest to, or farthest away from, the Sun respectively.  Extreme low tide must be avoided when planning an otter trawl in shallow marsh.


Bay-side station trawling results.


Upstream of Railroad Bridge.

Very wet rainy season + Late spring rain = fresher Lower South Bay.  Salinities at all stations were at least 5 ppt lower than typically registered by June in a “normal” year.  The impact on biota was conspicuous throughout the weekend.  Some unusual indicators are discussed below:

  • Pacific Herring
  • Sacramento Suckers
  • Prickly Sculpin
  • California Bulrush
  • Golden Anchovies, and more


1. Amazing Sunday

As shown below, Jim Hobbs, Rachel Fichman, and Pat Crain observed several unprecedented biotic occurrences on the Sunday / Bay-side trawls.  (Unfortunately, I unwisely chose to accompany the weekend trawls on Saturday.)


A pile of Pacific Herring.

Pacific Herring.  This pile of Herring was the first surprise from trawling on Sunday.  Young Herring have been few to absent by June in all previous years.  As noted in previous Fish in the Bay reports, the Herring are sticking around longer and getting more mature (green-backed) compared to previous years.

Apparently, this big Herring school was loitering in the freshness (5.4 ppt) at the upstream end of Alviso Slough.  It suggests a few possibilities:

  • Herring recruitment is much better than usual in 2019
  • In past years, young herring may have reared further upstream in Guadalupe River and Coyote Creek – upstream of UC Davis trawls.
  • Young Herring like the fresher water. (Something triggers them to head out to sea while still young, but for some reason, this group remains here as long as salinity remains low.)


Sacramento Suckers from Alv1.

Sacramento Suckers.  This is a native freshwater fish we rarely see in brackish marsh trawls.  We presume that suckers are still endemic in upstream creeks and rivers.  The current low salinity allowed this group to spread out farther downstream than usual.

These are young suckers; all around 2 inches in length.  Adult Sacramento Suckers can grow to over a foot-and-a-half.  These little ones could be siblings from one brood; a single spawn can deposit many thousands of eggs.


Sacramento Sucker Table. The table above indicates all Sacramento Suckers caught in UC Davis / Hobbs Lab trawls since 2010.  This is not a rare or endangered fish in California, just rarely caught in Hobbs’ trawls here.


Shrimp, Anchovies, and Submerged Aquatic Vegetation.

Shrimp.  So far, it looks like we may have another good shrimp year.  Native Crangon continue to dominate over non-native Palaemon and Exoplaemon.  The year-to-date Crangon count is already at 17,719. … This already exceeds all Crangon caught in years 2015, 2016, and 2017 COMBINED!

Anchovy numbers increased as waters warmed in June, which is expected.  Anchovies generally appear golden-green on the Bay side and vividly golden farther upstream in Coyote Creek as discussed far below.

Red Gracilaria.  The above photo also captured the summer-time reappearance of Red Gracilaria (a red algae seaweed:  Red Gracilaria seems to have been proliferating here since around 2016, but it always dies back when temperatures drop in winter.


Mudsnails along the waterline.

Eastern Mudsnails. On Sunday, Jim Hobbs noted particularly large masses of mudsnails along the waterline and in spartina stands near Alv3.  We often see a lot of these non-native, but now essentially native, snails.  They eat benthic algae off the mud surface and probably play a big role in nutrient cycling.


Eastern Mud Snail Closeup.

The 274 mudsnails recorded in data sheets above were only a small fraction of the total abundance on 2 June.


A friendly neighborhood muskrat.

Common Muskrat.  Jim and Rachel observed his muskrat swimming across the mouth of Lower Coyote Creek near station Coy4.  The muskrat swam around Jim’s boat, then climbed on the boat transom to take a break.  After a few minutes of rest and grooming, he continued his swim.


Leopard sharks.  Rachel showing off two of the three Leopard Sharks caught at LSB2.


Plainfin Midshipmen (top photo), Cheekspot Gobies (bottom)

Plainfin Midshipmen.  Some young Plainfin Midshipmen showed up on the Bay side in June.  This seems to be a regular annual occurrence.

Cheekspot Gobies.  Again, the short mouth (maxilla terminates forward of the eye) indicates that these tiny gobies in deeper waters near LSB are Cheekspots.


2. Slightly Less Amazing Saturday

Until I saw Jim Hobb’s photos from Sunday, I thought we had a pretty interesting set of Saturday trawls.  … However, I must admit, Herring, Sacramento Suckers, Mud Snails, Muskrats and Sharks are more exciting than Tires, Bulrush, Prickly Sculpin, and Fish Eggs.

Artesian Slough:  Jim Hobbs on the transom / muskrat resting platform, Steve Slater at right.

On Saturday, we were joined by one of Jim Hobbs’ colleagues, Steve Slater.  Steve is a Senior Environmental Scientist with California Dept. of Fish and Wildlife from the Stockton office.


Jim Hobbs and Steve Slater wrestle a tire from the net at Art1.

First catch on Saturday was a tire with bugs and a few fish.  


Striped bass with fat bellies.

Striped Bass.  We only caught 8 Striped Bass this weekend.  However, those that I saw looked well fed.


Tire bugs:  Corophium on left, gammarids on right.  (Bugs shown are not to scale.  Corophium are about half the size of gammarids.)


California Bulrush.  The most striking thing on Saturday was the tall lush appearance of California Bulrush along Artesian Slough, most of Coyote Creek, and even inside Pond A19.  I have regularly visited this marsh since I was a young City of San Jose employee in the early 1990s.  I don’t recall ever seeing bulrush looking so tall and vibrant.


Marsh Wren nest.

Marsh Wrens weave nests in the bulrush.  The nests are usually very hard to see, but with bulrush looking so green, I was able to spot several nests as we motored down Artesian Slough


Stands of California Bulrush in Pond A19 (top) and near station Art3 (bottom).

California Bulrush range greatly expanded this wet year.  New stands have appeared all the way to the western side of Pond A19 and far down Artesian Slough into higher salinity areas normally occupied by Alkali Bulrush or Spartina.

Ever since I started watching Pond A19 around 2012, California Bulrush has never established like it did this year.  We should expect to see some (possibly significant) die-back as salinity increases through summer.


Baby Crangon from Upper Coyote Creek.

Crangon.  I used to think that Crangon were adversely impacted by freshwater flushing.  I was wrong!  Crangon appear to love freshwater flushing – at least the young do.


Golden Anchovies on 1 June.

Golden anchovies!  This is another first.  I saw golden-green anchovies that seemed to arrive last month and about this time the previous year.  But these latest ones caught on June 1st are 24-carat gold.  They show some greenness in the head crest, so they must be of green-back heritage.  But the rest of the heads and backs are increasingly golden.


More golden Anchovies.

Does fresher water or warmer temperature make green-back anchovies appear golden?  Normally, Northern Anchovies live in the ocean where salinity is much higher and temperature is much lower than here.  It would be nice to know what makes our Anchovies so golden, don’t you think?


Green back anchovy from Dump Slough

Riddle me this!  The Anchovy shown above was caught at DMP2 on the same day.  This one shows the deep emerald green of a true green-back.  But, temperature was even higher and salinity even lower than where the gold-backs were caught????   I continue to think we have at least two, and possibly up to four, separate Anchovy populations that visit the Alviso Marsh Complex.


2. Photarium photography experiments.

I got a “Photarium” small fish viewing tank as an alternate means of taking photos of fish and bugs in water.  It has advantages and disadvantages which you can see below.


Prickly Sculpin, out of water versus in water (same fish).

Prickly Sculpin numbers continue to be off the chart this wet spring.  The year-to-date count is 229 Pricklys so far.  This compares with only 23 caught in 2014, ZERO in 2015, 3 in 2016, and 10 in 2018.


Slightly older Prickly Sculpin with Three-spined Sticklebacks in the Photarium.

2017 was the record-breaking “Year of the Prickly,” in which 406 were caught.  I doubt we will break that record.  Prickly Sculpin numbers should decline the rest of this year as marshes salt up.


Prickly Sculpin with young Yellowfin Goby: out of water at top, in water at bottom.

We continue to see very young Prickly Sculpin.  Pricklys may have spawned multiple times because of the extended fresh season.  Some fish species continue to spawn if physical triggers, like temperature and salinity, keep telling them to spawn.


Rainwater Killifish, out of water, in water (same fish).

Rainwater Killifish is a very hardy non-native survivor.  They invaded SF Bay sometime in the late-1950s.  This particular fish looks dramatically different in water versus out of water.


Shokihaze Goby, aka “Bearded Goby.”

Shokihaze Gobies are sometimes called “Bearded Gobies” because of the fleshy “whiskers” over the lower jaw and operculum.


Longjaw Mudsucker – two different fish.

Longjaw Mudsuckers out of water tend to look like they are smiling as they expand their buccal cavity to absorb oxygen from air.  Don’t be fooled: they prefer being in water.


Three-spined Sticklebacks look about the same in and out of water.


4. Polychaete of the Month.

This was one of two polychaetes caught at Coy1.

Above photos highlight the two pair of eyes and tentacle arrangement on a young polyhaete from station Coy1.  You can also clearly see the constricting blood vessel along its back (no heart).  (Blood flows to the head through the dorsal blood vessel then back down the body via another blood vessel on the ventral side.)


Same polychaete swimming in the Photarium.

Polychaetes can be surprisingly agile swimmers.  Also, notice the antennae array on its head.  This is an advanced worm.

  • This YouTube video describes experiments in European estuaries to measure polychaete impact on nutrient cycling and denitrification:  “Nereis polychaetes and effects on nitrogen and phosphorus cycling in estuarine benthos.”

If we are concerned about benthic rates of denitrification in Lower South Bay, we may want to study these worms in greater detail!


5. Gooseneck incident in Dump Slough.

The “Gooseneck” in Dump Slough.

We caught an unusually large number of fish at station DMP2 in Dump Slough:
543 Sticklebacks, 114 Pricklys, 37 Mudsuckers, plus a few others = 708 total.

We knew what had happened.  As Pat Crain brought the boat around a sharp bend in Dump Slough, a portion of the net plowed through a stand of California Bulrush in the corner.  Normally, we do not want to trawl through vegetation.  It is not good for the marsh, the net, nor the boat.  But, this inadvertent, and in this case almost unavoidable, incident does illustrate a point:  There are a lot more fish in the mash edge than in the mid-channel where we trawl.

I would go so far as to speculate that many of these fish flee to the edges when they feel the vibration of the Hobbs boat coming down the channel.  Many others, like Longjaw Mudsuckers, live in sheltered hollows among the tule roots.

This may be analogous to recent findings about the disproportionately large role that tiny “invisible” fish have in coral reefs:


6. Egg Cam

Exopalaemon eggs.  I noticed that I could see eyes and developing organs in Exo eggs under magnification.


Prickly Sculpin eggs?  Pat Crain suggested that this string of fish eggs might have come from Prickly Sculpin.  We collected it in Pond A19.  As with the Exo eggs above, developing embryos are visible.


Until next month…



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