Fish in the Bay – 10 February 2018 UC Davis – Larval Smelt Survey, in search of Longfin Spawn.

Today, I joined Jim Hobbs for one of his Larval Smelt Surveys.

This is a different kind of survey commissioned by California Department of Water Resources (DWR).  For a couple of years now, Hobbs and the UC Davis researchers have been towing fine mesh nets in Lower South Bay search of winter-time larval smelt.  Hopefully, this effort will map out the exact spawning Longfin Smelt range.  As you all know, Longfins are the next threatened fish after Delta Smelt, which are facing extinction.

This trip did not involve the big otter trawl nets.  Instead smaller, sled mounted, “Plankton Net”  and Clarke-Bumpus nets were towed in tandem.  (You can see the mouth of the Plankton Net next to Jim Hobbs in the photo above.  The smaller Clarke-Bumpus net is mounted next to it.)  The mission of this survey was to catch larval fish and tiny bugs they eat.

Area surveyed is shown in the google map image.  I did not mark specific survey locations because sampling was rather random (albeit locations were recorded).  Net contents consist of gelatinous goo that is sent to the lab for microscopic analysis.  Outside of random sticklebacks and maybe a herring larva or two, you cannot discern by eyeball exactly what was caught.  Despite that, and ironically, these might be the more biologically important surveys.

We already know from Hobbs’ otter trawls in December and January 2018 that Longfins are spawning in this area.  Spawning could continue so long as temperature stays below 14.5 degrees C and the water doesn’t get too salty.  Only Longfin Smelt have been caught here.  People ask me if we have seen, or expect to see, the critically endangered Delta Smelt.  Sadly, the answer is “No,” we do not expect to see Delta Smelt as they do not tolerate salt water above 19 ppt, and usually range in waters of 2 to 7 ppt.  There is too much salt water between Lower South Bay and the Delta.

BTW: Longfins and Delta Smelt are “True Smelt.” The fish family is called “Osmerid.”  Other true smelt are Night Smelt, Surf Smelt, Wakasagi (in Japan), Eulachon, and others.

An interesting article about Eulachon is here:  Eulachon populations, like Delta Smelt and Longfins, crashed in the early 1990s, though they have been bouncing around since then.  NOAA has Eulachon under a “recovery plan:”

Eulachon is just another example of a True Smelt that was once one of the most populous fishes in estuaries in the Pacific Northwest: a high food value fish that experienced huge population “booms and crashes” in response to environmental changes. Unfortunately, Eulachon, Longfins, Delta Smelt, and other True Smelts tend to be fragile little fishes that do not adapt well to major modifications to riverine and estuarine habitats, water supply, invasive predators or competitors, and such.

FYI: “Non-true smelt” are of the Atherinid family (AKA: old-world silversides), such as the Top Smelt, Jack Smelt, Grunion, etc.

Fun Fact about True Smelts:  Some say that all true smelt smell like cucumbers when taken fresh out of the water.  It is true that Delta Smelt and Surf Smelt have the cucumber odor according to reliable reports (e.g. )  However, Ryan Mayfield, assures me that Longfins do NOT smell like cucumbers.  (I have never personally sniffed our Longfins.  But, I promise, next time Jim Hobbs shows me an adult longfin, I will sniff it.)

More winter doldrums.  The winter marsh continues to be a gray world. Plants, birds, and fish all take on a gray cast.  The photo above was in Pond A19.  The avocets in the foreground and the Willits just behind them are wearing winter white-gray colors.  The marsh, to most human eyes looks almost dead.

Sticklebacks were almost the only adult-sized fish caught by Plankton Net, and dozens were caught.  This is interesting because over a total of 60 monthly otter trawls in December, January, and February, practically no sticklebacks were caught.  Only seven of them were netted on one occasion at the “Artesian 3” station in February – the highest number seen in over three months.  In contrast, these plankton trawls captured several to almost 40 of them.  It illustrates the limitations of any particular trawling rig: big nets catch big fish, little nets catch little fish.  Or to put it a different way, just because you don’t see sticklebacks in otter trawl surveys, doesn’t mean they are not there.  The sticklebacks below were caught in Pond A19.

Jim and Pat Crain informed me that stickle backs can be voracious predators of copepods and larval fish.  So, it makes sense that we find sticklebacks in the midst of all the tiny creatures.  Interestingly, this is also our local recruitment season for Pacific Herring.  I found this 2013 paper that researched the extent of stickleback predation on Atlantic Herring in the Baltic Sea:

Bottom line from the paper: “we … consider the three-spine stickleback to be the most important piscine herring-spawn predator within the Baltic Sea lagoons and estuaries.”

Image above shows how authors, Kotterba, Kuhn, et al, set up a portion of their experiment.

Stickleback showing his spines.  Saltwater sticklebacks are armored and have defensive spines.  It is a fish-eat-fish world down there.  Sticklebacks are eaten by striped bass and waterfowl.  But, I assume stickleback spines make them a little less appetizing.  Smelt and herring don’t have spines or other conspicuous defenses, so high reproduction rate is their strategy for evolutionary survival.

Big Copepods were found in Pond A19 and in nearby portions of Coyote Creek.

These were really big copepods with bright red eyes amongst numerous larval fish.

Copepod closeup:  I have never seen such big copepods – no microscope needed!  Granted, my copepod experience is very limited.  Most laval fish here are presumed to be different types of gobies, but hopefully careful analysis will reveal some surprises.

Further upstream on Coyote Creek. The jar held by Jim Hobbs gives an idea of what heaven looks like to a stickleback.  A broth of algae, copepods, larval fish and other tiny creatures that swim or float with the water column.

Closeup of the jar: lots of skinny white larval fish amongst the mass of plant fibers.  You can also see lots of small roundish copepods near the right and bottom sides of the photo.  The several plankton trawl results indicate that almost every point in Lower Coyote Creek, the Island Ponds, and Dump Slough are crawling with larval fish and copepods in February.

Plant life #1 – Cattails.  I noticed that that portions of Artesian Slough and Coyote Creek on the north side of Newby Island are flanked with dead cattails.  These areas are normally exposed to brackish tidewater that is too salty to support cattails.  The 2017 February Freshwater Flush temporarily upended the normal order.  It is amazing that cattails could colonize so quickly in a normally hostile place, then die off just as fast.

Plant life #2 – California Bulrush.  California bulrush takes over when cattails can’t.  Bulrush is the plant we usually see lining fresher portions of Coyote Creek and Artesian Slough.  But even California bulrush has salinity limits, giving way to shorter Alkali bulrush over much of the main stem of Lower Coyote Creek.  This year was a good example showing how winter rains affect the geographic range of different plant types.

Pacific Herring larvae?  Plankton net contents got a little thinner as we moved upstream on Coyote Creek; less algae, more vascular plant fibers to my naked eye.  There were still a lot of fish larvae.  The long, skinny, snake-like looking ones were of most interest.  Dr. Hobbs tells me that these are likely herring larvae, though longfins look very similar.  Longfins develop a conspicuous, triangle shaped swim bladder at this age.  I tried to spot a longfin bladder in these skinny guys, with no luck.

Bay Pipefish was the only other adult fish caught.  This one was caught further up Coyote Creek, on the south side of Newby Island.  The tiny mouth of this fish looks too small to swallow anything larger than copepod nauplii.

Fun Fact from Jim Hobbs and Pat Crain: Sticklebacks and Bay Pipefish (and sea horses and trumpet fish) are members of, once-thought-to-be-related, orders of fishes; sygnathaformes (means “conjoined-jaws”) & gasterosteiformes (means “bone-bellies”).  I later discovered they have at least one official fan club: the IUCN Seahorse, Pipefish and Stickleback Specialist Group –  Tube-like snouts, male parental care, and outer body armor seem to be some of the visible distinguishing characteristics of this group.  And, they are cute little fish that everyone seems to love!

Lots of sticklebacks a little further up Coyote Creek.  In this instance, Dr. Hobbs took us further upstream than normally surveyed by otter trawl.  The intent was to explore the limits of Longfin spawning.  This was where the most sticklebacks seemed to be.  If sticklebacks are an indication of herring eggs and larvae, or fish larvae in general, then we should find a lot of larvae here.

This is what “up the creek” looks like on the surface:  The UC Davis boat was too big to go further.  The creek is choked with bulrush past the north side of the “Recyclery” east of Newby Island.  After a few more Plankton Net trawls, we called it a day.

EPILOGUE.  Beach Seine the next night.  Jim Hobbs and the UC Davis research team are also finishing work on a “Mercury in Small Fish Study” funded by the Salt Pond Restoration Project.  This study consists of analysis of numerous small sticklebacks and Inland Silversides for mercury contamination.  Beach seine nets are used to collect small fish in Alviso, Guadalupe, and Artesian Sloughs.  On this occasion, Jim’s team was out on Monday night, after dark, slogging through the mud by flashlight.

It was cold.  I had a jacket on against the chilly breeze, and I was shivering after 20 minutes.  These guys were in the water!  I watched as Rachel Fichman, Wilson Xieu, and Michael Berientez unfurled the long beach sein net around a large area of water then hauled it back in to sort through the fish.

Ordinarily, I would not have stopped by to observe a nighttime beach seine. I would have been headed home in the evening commute, but Jim Hobbs had just sent me news that almost made me fall out of my chair; a spent female Longfin had just been recovered!  This was a female that had just dropped her load of eggs nearby.

The spent female Longfin!

You can imagine my excitement.  She was caught at the SJ-SC RWF boat launch, 350 feet from where tertiary treated wastewater flows to the Bay!  Somehow, this little threatened fish swam nearly 2 miles up Artesian Slough, toward the largest wastewater treatment facility in the bay.  She was seeking the ideal temperature, salinity, and substrate for spawning.  Finally, she picked practically the exact spot where treated wastewater discharges from 1/5th of the SF Bay human population.

This discovery would have been unimaginable up through the late 1970s.  Toxic metals, chlorinated pesticides, and low Dissolved Oxygen would likely have scared this fish away.  Treated wastewater is much cleaner today: we have data that shows this.

But, in complete honesty, a Longfin spawning at our outfall was unimaginable to me until today.  It was only last year, March and April 2017 that Hobbs first confirmed that Longfins spawn in Lower South Bay.  Now we find them spawning on our doorstep.

If we can all treat our wastewater to make this happen, we can do anything!

Jim Ervin
soon to be retired


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