Fish in the Bay – May 2022, Part 2: Leopard Shark Baby Boom.

These are additional notes from the May trawls.  As always, there are so many critters to discuss and so little time.  Leopard sharks, 50 of them, were a dramatic feature of the May trawls, but there was so much more.

1. Newborn Leopard Sharks in May.

Record Year:  50 baby sharks were caught in May.  Another 15 were caught and released during June trawls.  The year-to-date total now stands at 69 Leopards.  2022 is already our record Leopard Shark year!


Leopard Sharks at Alv2

Newborn Leopards eat tiny soft bottom-dwelling critters. No doubt they are eating well off of the May baby goby explosion, but young shrimp, amphipods, and polychaete worms are also on the menu.  On a few occasions, we observed newborn sharks spitting out half-eaten polychaetes.  These worms may be their favored food.    


Four baby sharks, an American Shad (top left), and a Pacific Tomcod (bottom left)  at LSB2, 1 May.


15 slightly larger baby sharks were caught the following month on June 12th.  – These four were from Coy3

Baby Shark Growth Rate.  It is satisfying to watch these sharks grow each month, from tiny 6-8” newborns around March thru May to 10-12” toddlers by mid-summer and eventually 24+” adolescents by year’s end.  

Hopefully, their surging numbers represent permanent improvement, not just another La Nina climate fluke.


2. Bat Rays and Sturgeon – The Other Predators.

Bat Ray at LSB1.

Bat Rays.  The Bat Ray season is off to a slow start.  Only six were caught in May.  Like Leopard Sharks, Bat Rays arrive in the warm season to birth their pups from spring through fall. 


White Sturgeon.  End of Sturgeon season.  

  • We typically only catch one or two sturgeon per year in the net, but we see many more on sonar.  We don’t always see them, but when we do it’s usually during the cooler months of the year.
  • Sturgeon physiology suggests that they avoid high temperatures and low dissolved oxygen during the warm season. They feed on the springtime surge in baby Gobies, English Sole, Staghorn Sculpin, and shrimp, then disappear as temperatures rise.   


3. Other ‘La Nina’ fishes?

Good News: So far, we have counted record numbers of Anchovies, Longfin Smelt, Leopard Sharks, and Yellowfin Gobies in 2022, the second back-to-back La Nina year. 

Bad News:  Contrary to expectations we did not see record numbers of Pacific Herring, Staghorn Sculpins, and English Sole.

2022 year-to-date totals thru May
English Sole          – 795 (a good but not great year)
Staghorn Sculpin – 291 (a poor year)
Pacific Herring    –     3 (a very bad year)


End of English Sole season in May.

Where did they go?  Both literature and our own trawling history suggested that Herring, English Sole, and Staghorn Sculpins are La Nina fishes.  Cool ocean upwelling feeds the adult population off the coast.  Adult Herring and Staghorns arrive in Lower South Bay around December thru February to spawn.  Baby English Sole migrate into the Bay each January thru March to feed and grow. 

But alas, the second year of our double-dip La Nina did little for Herring and Staghorns.  Only the English Sole showed up in modest numbers.


Staghorn Sculpin, English Sole, and Palaemon Shrimp at Alv2.

The cause for the weak performance of these fishes in this second La Nina year is unknown.

  • Could lack of rain have inhibited their recruitment?
  • Or, perhaps a surge in larger predators is controlling their populations?
  • See Weber et al (2021) State of the California Current 2019–2020: Back to the Future With Marine Heatwaves? This paper provides an interesting analysis of California Current System upwelling and finfish production. 

“The relatively strong biologically effective upwelling in late winter 2020 was the first to occur in many areas of the central and northern California Current System (CCS) since before the Marine Heat Wave (MHW) in 2014 (although a weaker event occurred in winter 2018; Figure 6). Winter upwelling likely was important not only in supporting production directly but also in preconditioning the system for increased production in the spring (Black et al., 2010).” 


4. Oddball Marine Invertebrates.

Scale Worms are sort of like carnivorous earthworms.  They occupy a niche somewhat between a terrestrial centipede and millipede; eating whatever they can catch or scrape off a rock. They are amongst the most common benthic critters found in oceans around the world.  The dry drought years make LSB more hospitable for them.


Orange striped Anemone (Diadumene franciscana?) at Coy4.

Orange striped Anemone.  Like scale worms, these tiny anemones continue to be very common with the dry years.  These are very attractive anemones if you have a magnifying glass.  The biggest is about 1 centimeter across.   They appear to detach and drift/roll around when they need to move to a new location.  We continue to find many specimens at far upstream stations.


Nereid Polychaete.  These small worms measure about 1 to 3 inches. They are similar to our more common “Pile Worms/Rag Worms” but smaller and much skinnier.  I call them “long skinny worms” for want of a better name. 

  • They have at least one pair of eyes and three pairs of antennae on their heads. That should narrow their identity down to some variety of Nereid Polychaete.   
  • Can anybody identify this species?


Blood Mysids at LSB2.

Blood Mysids.  A different variety of Mysid appears to reside at the deep Bay stations; LSB1 and LSB2.  These typically show a red spot just behind the head and tend to have a pinkish appearance, hence the nickname ‘blood mysid.’  What mysid is this?

Mysids are essentially midget shrimp or krill, albeit, they are not true shrimp.  Their populations bloom to massive numbers under the right conditions in estuaries and along the coasts.  They are amongst the most important foods for both small and large fishes. 

We presume that most of the mysids we catch at upstream stations are native Neomysis kadiakensis. But, what is the identity of these saltier ‘blood mysids?’  The Bay has at least three other species known to live in higher salinity water according to the CDFW Mysid Key (2006).

  • Alienacanthomysis macropsis, native, low salinity to marine, prefer high-salinity
  • Acanthomysis hwanhaiensis, Korea, low salinity to marine, prefer mid-salinity.
  • Acanthomysis aspera, Japan, fresh to marine but prefer high-salinity

Mysid identification is tricky.  More investigation is needed.

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