Fish in the Bay – May 2024, El Nino?

Relatively few fish overall.  May totals were generally not the lowest ever, but these numbers were reminiscent of low fish totals we saw in some of the earlier years of 2010 to 2016. 

Is it El Nino?  According to legend, Peruvian and Ecuadoran fishermen discovered that sea surface temperatures turn especially warm around Christmas time every few to several years. (They called it El Nino, “baby boy” in reference to the Christ child.)  

  • Unfortunately, fishing sucks when El Nino hits. That’s because the surface warmth slows down cool ocean upwelling along the west coasts of North and South America. 
  • Our own experience here in Lower South SF Bay seems to corroborate these ancient observations. With exception of Halibut and possibly California Tonguefish, other fishes become scarce during El Nino.      


Only three fish in Artesian Slough!  This is not the first time that we caught so few fish there, but it is always a bit unsettling.  Artesian is usually attractive to fish by being a little warmer and fresher than adjacent slough segments.  This was one of those times when it provided neither advantage.

Most Yellowfin Gobies (290 out of 350 for the weekend) were caught in Dump Slough and Pond A19.  That may define the rough epicenter of this year’s Yellowfin spawning zone.


Only 24 Anchovies for the weekend – all but 3 downstream.

Baby Longfin Smelt.  Four tiny baby Longfins were spotted in May otter trawls. This was far short of our hopes and expectations.  But, at least this confirms that Longfin spawning was again successful. 

  • Fragile babies flee to deeper cooler waters quickly. We anxiously await the next Longfin return in October or November.


1. May was the new March.

According to the old saying, “March comes in like a lion and goes out like a lamb. 

  • This season was different. Cool and wet winter weather persisted intermittently through early May.

In like a lion:  For our trawling day on Saturday May 4th, we showed up mistakenly expecting slight rain and mild temperatures.  Dressed in windbreakers and light clothing, we were all unprepared for the freezing downpour that persisted until mid-afternoon.  To make the experience even more uncomfortable, the day was punctuated with minor equipment failures, two aborted trawl attempts due to mud balls, and a temporarily fouled propeller. 


Out like a lamb:  May 5th was sunny, pleasant, and wonderful.  It felt like a different season. Fish and bugs must have been feeling this climatic variability as well.

Interesting El Nino connections:

  • Jacox et al (2024) Linking Upwelling Dynamics and Subsurface Nutrients to Projected Productivity Changes in the California Current System
    “Despite models’ diverging projections of productivity changes, they agree that those changes are predominantly driven by subsurface nitrate concentrations, not by upwelling strength. Our results highlight the need for more attention to processes governing subsurface nutrient changes, not just upwelling strength. …Across models, phytoplankton biomass changes are more closely tied to subsurface nitrate concentration than upwelling strength.”


2. Extra Baby Fish Month.

Yellowfin Goby count = 350.  The Yellowfin Goby spawn continued through May.  This is an extension of April’s “Traditional Baby Fish Month.” 


Other baby fishes.

Northern Anchovy count = 24.  About half the Anchovies were long skinny babies. Adult spawners tend to arrive in June or July.

Longfin Smelt count = 4.  All four Longfins were tiny post larval juveniles.  Adult Longfins have retreated to cooler deeper waters.


3. Water was still fresher than usual.

Pacific Herring count = 5.  All Herring we intercepted were recently hatched juveniles making their way out to deeper waters. 


Starry Flounder count = 6.  Five of six Starries were caught at UCoy1.  Starries dropped to their lowest total in May and then dropped again to only three in June.  The “Year of the Starry” ended abruptly.  This is a bitter disappointment.  

Sacramento Sucker count = 2.  Extended rains and fresher water continued to encourage Sac. Suckers to venture downstream into our trawling area.

Striped Bass count = 9.  


Fish trophic web at station Coy1:

  • Pregnant male Pipefish feed on rotifers and copepod nauplii.
  • Juvenile Pacific Herring feed on copepods as they grow and migrate out to sea.
  • Baby Halibut ambush young Herring, Anchovies, shrimp, etc.
  • Young-of-year Striped Bass eats whatever it wants.


4. El Nino brings us Halibut.

Young Halibut at Coy4.

California Halibut count = 37.   Young Halibut continue to show up.  The year-to-date count is already 120. 


The Halibut – El Nino connection is readily apparent here: These are the highest Halibut numbers we have seen since just after the last big El Nino in 2014/15.   

Staghorn Sculpin count = 2.  (no photo).  This was our lowest ever May count for Staghorns.  The previous record low count for May was 31 in 2015.  Clearly, El Nino is not good for Staghorns.  We usually catch dozens to a few hundred young Staghorns this time of year. 


5. Interesting oddballs.

Bay Pipefish count = 9.  These tiny slough-dwellers don’t migrate far from home, hence they are more influenced by local weather as opposed to the greater ENSO-type ocean cycles.


Pipefish numbers tend to increase in warmer and drier years though.  Fresher water from this spring’s extended rainy season continues to keep them pushed farther downstream than usual.    


Sami shows off the puffy cheeks of a territorial male Shimofuri at Coy3

Shimofuri Goby count = 30.  Shimofuri numbers are typically low early in the year.  Then, they explode from late summer through fall after the peak of their warm season spawning. 

  • Larger territorial males establish nesting burrows or hollows. Their cheeks swell as they prepare to attract females and fight off other male competitors.


Thanks to information from researchers at the Biological Laboratory of the Imperial Palace (BLIP) in Japan, we now understand that puffy cheeks in Shimofuris and most other gobiids can be interpreted as a sign of male spawning readiness.  


Each fish and bug tells us a story.  We are learning to read the clues. 

Good news!  This current El Nino was strong but of very short duration.  According to NOAA, it has already ended. 

“The tropical Pacific’s climate pendulum appears to be swinging back toward its other extreme: La Niña. In the Pacific, La Niña brings cooler-than-average temperatures in the central-eastern part of the basin, stronger winds both near the surface and at high altitudes, …. The forecasting team thinks there’s a 65 percent chance that La Niña will arrive by July-September.”

Will La Nina bring the fish back?  Hypothesis testing continues.

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