Fish in the Bay – 17-18 February 2018 UC Davis Trawls – A Blustery Day.

Hello everyone.  I am now a retired guy, and this is my first fish email from the retired side.  Family matters and some procrastination have put me behind.  This is my second submission for February.

I went out with the UC Davis / Jim Hobbs fish researchers twice in February.  The Hobbs team performed a larval smelt survey on February 10th that I emailed about several weeks ago.  Then, they came back to perform the regular fish and mysid population surveys the following weekend of 17-18 Feb.  Increased monitoring these past couple of years is showing that Lower South Bay may be the new epicenter for Longfin Smelt spawning in the Bay particularly after the 2016/2017 wet winter.  This is mixed-news at best:

  1. Very good news that Longfins spawn down here;
  2. Bad news that Longfins have declined to such an extent in northern parts of the Bay and Delta.

Bird Watching.  Before I met with the boat crew on Sunday, I stopped by Curtner Elementary School in Milpitas to check on the bald eagle nest, then arrived at the boat launch on Artesian Slough to document interesting birds as I waited for the boat.  These are some of the many birds that feed off our beautiful fish and bugs.

Bird Key:  A. Bald Eagle, B. Great Blue Heron, C. Black-Crowned Night Heron, D. Snowy Egret, E. Northern Shoveler, F. Green-Winged Teal, G. Greater Scaup, H. Green Heron, I. Pied-Billed Grebe, J. Cinnamon Teal, K. Ruddy Duck.

I don’t give birds a lot of attention in my emails because 1) my Nikon Coolpix S9700 camera is not adequate for birding – and a better camera might not survive long on a rocking boat, and 2) there are many, many talented bird photographers in the Bay Area.  But, it makes me a little sad and frustrated that I generally must leave images of avian life on the cutting room floor.  So many important and fascinating birds!

Less than 20 minutes later, the Hobbs crew showed up at the Artesian Slough launch, and bird watching was over.  Time to look at fish!

As usual, the UC Davis team trawled, or attemped to trawl at 20 stations: 10 on Saturday, 10 on Sunday.

Saturday, 17 Feb – Bay-side trawls

Sunday, 18 Feb – upstream and east of the Railroad Bridge

February fish numbers were again low, which is typical for winter.  But, continuing high numbers of American Shad and Threadfin Shad are very encouraging.  These two species, like Longfin Smelt and Prickly Sculpin, recruited well due to the big freshwater flush in early 2017.  I am still amazed that an event as specific as a big storm in February 2017 continues to influence fish populations a year later.

Striped Bass. Hobbs Lab researcher and Facebook friend, Malte Willmes, joined us on this trip.  Above, Malte admires a very well-fed Striped Bass, one of the first fish caught on Sunday.

American Shad & Threadfin Shad.  The next trawl, at station ART-2 midway down Artesian Slough, yielded a small tray full of Threadfin Shad and two American Shad.  An American Shad is near the center of the group below.  He is a little longer and with four or five small dots behind the bigger black dot behind his gills.  Body shape and the “thread fin” are other clues.  To untrained eyes, a shad is a shad.

Both types of shad are non-native, but generally not considered a problem in California.  Every time I see one, I think, “What a pretty fish!”

Corbula.  Young invasive corbula clams were also picked up at the same location.  Filter-feeding corbula had a profound adverse impact after they established in Suisun Bay in the mid-1980s.  For that reason, I continue to collect them rather than toss them back.

More green water.  Above, Jim Hobbs gazes at green water flowing out of Pond A18.  That is the difference that phytos make.  It’s all the same water, just different residence times in sunny South Bay.  For some reason, phytoplankton, over many days to weeks in a slow-moving pond, make pond water look vivid green.  Pond A16 shows the same effect most of the time.  The greenness seems to have no effect, good or bad, on fish, benthic critters, or other phyto populations in, or outside, the Pond.  But, what is making the water look green?!?!?

Three spined Stickleback.  There were only a few Three-spined Sticklebacks caught on Sunday.  This was a nice looking one showing his spines.  I learned the prior week that Sticklebacks are voracious predators of larval fish, particularly herring larva.

Mysids. We caught a lot of mysids.  These are tiny shrimp-like critters that fish and whales like to eat.  When people refer to “krill,” mysids are part of the overall krill community off some ocean coasts and in estuaries.  A few years ago, I risked parasite infection and ate some.  I can attest, they taste like shrimp and are absolutely delicious.  Looking back, that was foolish.  Don’t do what I did.

Windy day.  We encountered strong wind as we left Artesian Slough and motored out into Lower Coyote Creek.  It is surprising how much wind-shelter the small 2-to-3-foot-high levees provide.  As soon as you move beyond that small screen, boom … the wind hits you.  We later found that trawling the east end of Pond A19 was impossible due to strong wind over the open water.

Snowy Egrets decided to huddle down behind the levees for wind protection at different places.

Staghorn Sculpin.  Two plump Staghorn Sculpin were netted at the Coy-1 station.  We didn’t catch a lot of fish, but those that were caught appeared to be particularly well fed.  Also notice the white markings over eyes and forehead of one of these sculpins:  I don’t know the significance, but I have seen this color pattern in others.

Prickly Sculpin.  Later in the day, Prickly Sculpin were caught further upstream in Upper Coyote Creek and Dump Slough – one each.  Photo above shows a Prickly and Staghorn Sculpin for side-by-side comparison.  This Prickly would have hatched further up in Coyote Creek the previous winter.  The big February Flush of 2017 washed him (or her) downstream.  Now it is fighting its way back up Coyote Creek to return to the spawning grounds, hopefully not too late.

As far as I know, the Staghorns may be spawning right in these downstream locations where we survey, as indicated by some of the babies you will see further down.

Strontium sampling.  Among other tasks between trawls, Malte collected water samples for strontium isotope analyses.  A Hobbs Lab specialty is study of fish “otoliths” (aka “ear stones”).  The ratio of strontium isotopes varies by water body and becomes embedded in otoliths as fish grow.  So, by collecting extensive strontium data, researchers can figure out where a given fish spent key portions of its life, after the fact, of course.

Fish Diversity in Dump Slough.  This was the other Prickly Sculpin caught in “Dump Slough,” formally known as “Coyote Creek Bypass Channel,” or Coyote Creek South Slough.”  The main marshes along tiny Dump Slough were partitioned off as part of Salt Pond A18 until levee realignment in 1988.  Those marshes now support a robust estuarine community of fishes and birds.  It looks like a garden of Eden to my untrained eye.  But, Dump Slough is still substantially cut off from periodic creek flow except during particularly high storm flows as happened in February 2017.  Pricklys were seen for the first time in Dump Slough after the February Flush and continue to be caught.  The Hobbs team also caught a few Longfin Smelt in Dump Slough over the past year.  I hold out much hope for Dump Slough as an underused flood plain habitat.

More Threadfin Shad.  Most were caught in Dump Slough.

Bay Pipefish.  One of my favorites, also from Dump Slough.

Baby sculpin.  We saw something a little more unusual in upstream stations: three very tiny Staghorn Sculpin.  This is a positive sign that Staghorns are spawning nearby, as they should.   According to the UC Davis website, California Staghorns spawn in January and February ( ).   I already know, and will report next week that we saw more tiny Staghorns in March.  These may be indications of a good Staghorn recruitment this winter.

Mysids.  Baby staghorns should have plenty of mysids to feed on as they grow.  Here is another handful of mysids caught at the UCoy1 station where the pair of babies were found.

Longfin Smelt.  This was the single Longfin Smelt caught on Sunday in Pond A19.  Longfin numbers are expected to decline after the end of winter spawning season with increasing temperatures.  However, the three caught in February is deceptive.  Several more were caught the following month in March.

Mysid Net Jars.  In addition to otter trawls for fish, Jim Hobbs and crew sample using a smaller Mysid Net and Clarke-Bumbus Net.  These survey populations of very small organisms.  When I accompany the UC Davis trawls on Sundays, I try to photo analyze the Mysid Net jars.  This provides a nice “snap-shot,” so to speak, about tiny food at different points in the estuary.

Above is Jim Hobbs taking his snap-shot from the other side after we landed back at the Artesian Slough launch.

These are the jars arranged left to right, from salty Bay-side to upstream stations.  (The Alviso-3 jar is deep red owing to red Rose Bengal dye in the sample.)

Larval Fish.  It was hard to see by naked eye, but fairly clear in the photo that there were a lot of unidentified baby fish in the sample from Pond A21.  These were probably gobids and/or sculpin.  Longfin Smelt and Herring larvae would look long and snake-like.

Ctenophores.  The two samples from far out in Lower South Bay (LSB) contained a lot of comb jellies, or ctenophores, if you prefer the scientific name. You can see at the bottom of the Saturday data table that I added a line for comb jellies caught by otter trawl.  Those numbers do not include the comb jellies seen in these jars.

Ctenophores, pronounced “Teenofores,” are not closely related to what we otherwise call “jellyfish,” aka: Medusae.  In fact, a Scientific American article from 2013 claims that Ctenophore genome studies suggest that these may be the most ancient form of animal life.

Of greater importance here, I have noticed that Ctenophores tend to show up in large numbers around December or January.  This is the same time that we also tend to see blooms of tunicates (sea grapes) on the bottom.  It continues to puzzle me that these filter feeders would invade in winter when the supply of phyto and zooplankton is at its low point for the year.  Dr. Hobbs suggested that cold temperatures may favor both unrelated life forms.  So, maybe these are part of a polyphyletic cleanup crew … arriving with winter cold to harvest excess planktonic life after another productive year??  They look more like soap bubbles than scrubbing bubbles, but they don’t appear to cause any harm to fish, birds, or humans.


That’s all I have for now.


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