Fish in the Bay – February 2020: Comb Jelly Explosion!

No rain = fewer fish!  An unseasonable winter dry spell continues.  Lower South Bay continues to get saltier.  Based on only a few years of data at my fingertips (2017 – 2019), this was dry but still almost typical for early February.  But, we have had no rain since then!  Generally, less rain means fewer fish.

I prefer more fish, so Pray for rain!


Trawl map.


Bay-side station trawling results.


Upstream of Railroad Bridge.

On the plus side, we caught over 3,000 comb jellies and several other unusual (for Lower South SF Bay) saltwater critters.


1. Unusual Appearance of Salty Ocean Critters Continues.

White Sea Bass in Pond A21.

White Sea Bass. This is the third White Sea Bass caught in Lower South Bay trawls since 2010.  The previous two were also babies and both netted in 2016.  Sea Bass normally live in schools near kelp beds off the coast.  Juveniles, like this one, lose the dark-colored bars as they grow.  They can grow to well over 50 pounds in the ocean. 

Somehow, this young one drifted into the Bay.  Unseasonable high salinity must have drawn him further south than normal.   


Pacific Herring at UCoy2

Pacific Herring adult.  Baby Herring are common by around March in Lower South Bay, but adults have never been caught here – UNTIL NOW.  I had never seen a Herring adult.  This one was 180mm / 7.1 inches long.  It looked like a mid-sized round and fat American Shad at first glance.  …  It must be delicious!  However, this fish was returned to Coyote Creek unharmed.  He, or she, was far upstream.  What a surprise!

Herring adults are known to spawn in North and Central SF Bay, and millions of larval fish drift to all parts.  We can only guess that this wayward adult meandered this far south in the Bay with the high salinity.  (However, always consider that fast-swimming adult Herring could be routinely evading our trawl net!  Who else is looking for adult herring in Lower South Bay???  Could adult Herring also drop their eggs here?)


Decorator Crabs!  Baby Decorators continue to show up.  We went at least a few years without seeing them.  Now they are back – all the way upstream as far as Pond A21.  This could be a big spawning event for Decorators further north in the Bay.  Is anybody else keeping tabs on San Francisco Bay Decorators?


Heptacarpus shrimp from LSB2

Heptacarpus Shrimp (Stimson’s Coastal Shrimp) were again caught at LSB stations.  


Two more Heptacarpus shrimp from LSB2

As always, the physical appearance of Heptacarpus shrimp varies widely: some are banded red, some are banded black.  This time we caught the white-and-tan odd-ball shown above (two views of the same shrimp).  These may represent more than one species.


Blue Anchovies – babies at LSB2.  I now firmly believe that iridescent blue crowns on baby anchovies tell us that salinity was high at time of hatching and early recruitment.  Maybe salinity is only part of it, but I am sticking with that story for now.  

We need to determine how precise this bright neon indicator is.  With Shad, their colorful salinity indicator is fairly precise – accurate to within 2 ppt in three-minutes!  For Anchovies, who knows?  A lot of things may affect a fish’s color.  We can figure this out!


2. Attack of the Ctenophores (Comb Jellies)!!!

Ctenophores filling the tray.

Ctenophores (pronounced “Teen-O-For” or “Ten-O-For”), AKA Comb Jellies, could be our best indicators when salinity is high in winter.  We generally see a lot of them in dry winters and few of them at any other time.


Beautiful Ctenophores in the hand.

This was a text-book Ctenophore bloom explosion.  These little gelatinous blobs are hermaphrodites that reproduce while still young.  When conditions are right, they reproduce like crazy.

Are Ctenophore blooms good or bad?  I think these are very good, but with Ctenophores it can go either way!

Chandy et al. (1995) “Estimating the predatory impact of gelatinous zooplankton”  reports:  “Cenophores can be extremely important predators in the food chains of coastal (Reeve 1980) and open-ocean ecosystems (Swanberg and Bgmstedt 1991). Larson (1987) has shown the large impact ctenophores can have as consumers of euphausiid [planktonic crustacean] eggs and larvae where they can compete with salmon and other juvenile fish for these same prey. Reeve et al. (1978) stated that ctenophores often act to balance the ecosystem by restraining an overabundance of copepods from virtually eliminating all phytoplankton from the water column.”


Ctenophore in the Photarium.

The name Ctenophore means “comb bearer.”  In this case we can see three of the eight rows of ciliated “combs” along the sides of this jelly.

They say Ctenophores may be among the oldest complex animal life, “… dating as far back as the early Cambrian, about 525 million years ago.” ( )   Albeit, there is still some ambiguity in the genetic record.  In any case, they have been around long enough that more complex lifeforms evolved to live in a world shaped by Ctenophores, not the other way around. Ctenophores form a “clean-up crew” that keep crustacean populations from going haywire.

Key Question:  What eats them?  A number of fish and benthic critters CAN eat them, but I do not yet know specifically how these transparent blobs of carbon get cycled here.  This is a missing piece in the nutrient puzzle.  The Wikipedia “Ctenophore” article suggests some ideas: 

It is … often difficult to identify the remains of ctenophores in the guts of possible predators, although the combs sometimes remain intact long enough to provide a clue. Detailed investigation of chum salmon, Oncorhynchus keta, showed that these fish digest ctenophores 20 times as fast as an equal weight of shrimps, and that ctenophores can provide a good diet if there are enough of them around.

…. Since ctenophores and jellyfish often have large seasonal variations in population, most fish that prey on them are generalists and may have a greater effect on populations than the specialist jelly-eaters. This is underlined by an observation of herbivorous fishes deliberately feeding on gelatinous zooplankton during blooms in the Red Sea.[58]


Ctenophore closeup.

We counted over 3,000 of these interesting animals over the weekend.  .  They were at all but the eight most upstream stations. 

If someone probed and sampled the semi-digested material in middle of the gut shown here, we could identify exactly what this Ctenophore ate over the last several hours.  Maybe we could figure out precisely what copepod or other crustacean foods make Ctenophore populations EXPLODE like this.  … Then, which diatoms or other phytoplankton feed the copepods … This nutrient puzzle is complicated, but it’s not THAT complicated!


3. Bay Gobies!?!?!?!

The last Bay Gobies caught in Lower South Bay – until now.

Bay Gobies.  Native Bay Goby was once numerous here in Lower South Bay.  They were commonly caught in otter trawls in the 1980s.  As recently as 2012, UC Davis trawls caught 12 of them.  Then, Bay Gobies disappeared!  Only TWO (2) were caught over the last several years!!!  They are still present in South Bay to the north, but essentially gone from Lower South Bay. 

Why did Bay Gobies leave?  I am sure that competition with non-native Yellowfin, Shokihaze, and Shimofuri Gobies exerts big pressure on them.  There could be other factors.


Have Bay Gobies returned to Lower South Bay???  One from LSB1 and one from LSB2 shown above. 

Big surprise, we appear to have caught at least several juvenile Bay Gobies at LSB1 and LSB2 stations in February.  These could be spawn from Bay Gobies to the north.  And, it is possible that we had not noticed tiny baby Bay Gobies like these in the past.  They are difficult to identify by naked eye on the boat. 

– notice the interrupted pattern of dark melanophores along the sides.  This appears to be the identification key.

Are Bay Gobies are returning?  … We shall keep watching.


4. Crangon brooding

Berried Crangon at Alv3.

There is no happier sight to see than berried Crangon in winter!  I hope this dry period doesn’t impact the recruitment of little ones.  Literature tells us that this dry period will probably hit them hard.  We need rain!  Quickly!


Crangon franciscorum in various states of maturity shown above:

  1. Year-old females with light-colored racks of eggs against their bellies (center and far left).
  2. Slightly younger females with growing tan-colored egg masses just behind their heads, and
  3. Smaller immature (male?) Crangon (uppermost in the photo).


More Crangon:  Black-tail (C. nigricauda) and Brown-tail (C. franciscorum) at Coy4.

Salty winter water brings the Black-tails back.  Crangon nigricauda are well known as being more salt-tolerant than Crangon franciscorum.  In Lower South Bay we rarely see Black-tails (C. nigricauda) except during periods of sustained high salinity. 


Berried Crangon at LSB1.

Both brown-tail and black-tail Crangon were berried in February.  Their sexual cycles seem to be on the same time schedule.  I continue to wonder if these really are two different species, or if they are different species, whether or not they readily hybridize here.


LSB2: more berried Black-tail and Brown-tail Crangon.

What if black-tails and brown-tails are NOT two separate species?  Could that be possible?


Crangon nigricauda.  These black-tails have light tan “tiger-stripe” patches.  Do these represent a different sex or life-stage?  Or does higher salinity cause these Crangon to form a banded pattern?  Tiger-striping could be common, but I have not noticed it before.


More tiger-striped Crangon from LSB1.  Three of the four Crangon shown above would easily be classified as Crangon nigricauda (black-tails).  However, second shrimp from the top has a brown tail, with all other tiger-stripes being the same.  Clearly, this bunch is all the same species.  

According to the Crangon literature, these are either C. nigricauda or C. franciscorum.  The color of the tail is the naked-eye identification key.  But, these tails appear to be telling a different story.


5. Other interesting fish.

Two English Sole from Saturday: dorsal and ventral views.

English Sole.  As usual, both English Sole caught on Saturday had visible parasite infections.  What’s up with this?  Why are debilitating parasites a characteristic of this species?


Yuckko!  Nasty tumor closeup from English Sole at Alv3

English Sole infection.  I don’t plan to get deeply involved in diagnosing English Sole parasite infections.  But, if someone is writing a book or paper on the subject, these photos are for you!


Speckled Sanddabs from LSB1.  Baby sand dabs never seem to have external parasites, nor do the adults.  None that I have noticed anyway.  The same is true for Halibut, Starry Flounder, and Diamond Turbot.  The only flatfish nearly always covered in parasites is English Sole!


Micah showing off our Leopard Shark of the day.

Leopard Shark!  We generally catch a few young Leopard Sharks each year.  Dry years tend to favor them.  They get clobbered when it rains too much – as it did in 2017.  But, they are still around.


More pregnant Prickly Sculpins at Alv1 in February.

Pregnant Prickly Sculpin, again.  As in previous months, we continue to see pregnant pricklies.  Pat Crain tells me that pricklies are more common in the upper Delta over the past year as well.  This is a Baby Boom generation caused by California’s extended rain in 2019. 

Prickly Sculpin spawn repeatedly when conditions are right.  But, their continued presence in the salty Alviso Marsh Complex is now a paradox.  Adult pricklies can tolerate high salinity, but Prickly fry might be more sensitive.  If so, we may see fewer of them next year.


6. Something different – Mud Snail Eggs.

Snail egg explosion!  I believe these beige-colored egg capsules are from Eastern Mud Snails (Ilyanassa obsoleta).  Those are the most numerous snail we see around here.  Adult snails concentrate around station Alv3, at the mouth of Alviso Slough/Guadalupe River. 


More snail eggs!

We encountered hundreds of tiny egg capsules at each station from Alv1 downstream to Coy4 and then upstream on Coyote Creek all the way to Pond A21.  At least 30 or 40 eggs are packed into each egg capsule.  That’s a lot of snails!

This must be snail egg season.  The snails lay eggs on every type of solid matrix material.  Adult snails often carpet the shore-side near the waterline at Alv3.  They consume algae on the surface of the mud.  At least a few important critters, like diving ducks or sturgeon eat the snails, and probably the eggs too, otherwise, snails would be filling the Bay by now.


More rain, please!

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