Fish in the Bay – June 2022, Record Anchovies and Gobies!

The fishes are now solidly in their summertime regime:  Anchovies, Gobies, baby Sharks, and Bat Rays.  Cool water fishes have retreated to deeper waters. We usually refer to the warm season in Lower South Bay as “Anchovy and Goby Season.”

Anchovy explosion.  See Fish in the Bay Alert from last week:   Spawning Anchovies have arrived!

Goby population explosion. The distribution of gobies in trawl catches was unusual.  The largest numbers were netted at downstream stations: Coy1, Coy3, Alv3, and LSB2.  Relatively few gobies were found upstream or in the ponds.


There was an interesting inverse relationship this month: where Anchovies are numerous (upstream and in the ponds), Gobies are scarce, and vice versa. 

  • On the map above, I highlighted four trawling stations where 300+ gobies were caught: Coy1, Coy3, Alv3, and LSB2. These are generally more downstream and deeper water stations. 
  • Attractions? I am not sure what attracts gobies to these particular downstream stations other than being in the main deep channels and places where the most detritus accumulates.
  • Repulsions? Perhaps thousands of Anchovies are simply gobbling up all the tiny food at upstream stations. Gobies may find little to eat when Anchovies crowd in like that. (Dense congregations of Anchovies would also draw down dissolved oxygen.  However, gobies are very tolerant of low DO, so I doubt that would discourage them.)


Shrimp wars.

  • Unfortunately, native Crangon shrimp are once again declining as summer waters warm. There was no apparent reason for an abrupt decline in Crangon numbers after June 2021.  Now it seems to be happening again.   
  • All three varieties of shrimp were scarce at upstream stations. Palaemon and Crangon shrimp were most abundant where gobies congregated and scarce at upstream stations with many Anchovies. This again supports the notion that Anchovies may have been scavenging all available tiny food at upstream stations. 


1. Tales from the fish nursery – Gobies and Toadfish.

Young Yellowfin Gobies, Art3, 11 June 2022.

Bad News!  Non-native Yellowfin Gobies are at a record high. Both May and June were record months with 2,363 and 1,899 Yellowfins respectively. 2022 is now our record Yellowfin year.  

Yellowfin numbers declined in 2019 and 2020.  This led us to suspect that the newest invader, the Shimofuri Goby might be crowding them out.  But alas, the Yellowfins are back.  This Goby Battle continues!  


Arrow Gobies and two young Starry Flounder, Pond A21, 12 June 2022.

Good News!  Arrow and Cheekspot Gobies also are at a record high: 1,142 of them were caught and released in June. 

Arrow gobies (Clevelandia ios) and Cheekspot gobies (Ilypnus gilberti) are small native gobies in West Coast bays and estuaries.  Adults of either species grow to about 2 inches long. They are extremely common and very important in estuarine mudflat ecology.  They serve as food for larger fishes and birds. These small gobies eat tinier organisms like copepods, worms, algae, and such. 


Arrow Gobies have bigger mouths and more sinuous bodies.  Arrows are more adapted to life on a soft mudflat in shallow brackish warm water. 


Cheekspots have tiny mouths, arched backs, and more distinct blue-black iridescent patches on their ‘cheeks,’ aka opercula.  (To make matters confusing, the blue-black spot is not always visible, and both Arrows and juvenal Yellowfin Gobies can also sometimes display a dark spot on each ‘cheek.’) 


Arrow/Cheekspot spawning.  Literature suggests that Arrow Gobies tend to spawn in late winter through spring, but both Arrows and Cheekspots may spawn throughout the warm season.  We seem to see more gravid Arrows in spring and gravid Cheekspots throughout the summer. 


The only Shokihaze Goby caught in June, LSB2.

Shokihaze Goby. Only one Shokihaze was caught in June.  None were caught in July. From 2015 through 2020, Shokihazes were our second most common gobies after Yellowfins.

  • When Shimofuri Goby numbers spiked after mid-2021, Shokihaze catches plummeted.
  • Shokihazes usually concentrated along a corridor from lower Alviso Slough to the deep LSB stations when they were plentiful. Perhaps, not coincidentally, the majority of Shimofuri Gobies now occupy that same corridor.    


Plainfin Midshipman.  We caught 33 Midshipmen this month.  All of them were tiny one- or two-month-old babies caught at downstream stations and in Lower South Bay itself.  These little ones hatched from eggs that were guarded in underwater caves by adult males (Singing Toadfish) for 40 to 45 days.   

Midshipmen are strange but impressive-looking members of the big-headed Toadfish family.  So far, we only occasionally catch adults near the start of their spawning season between January and April.  Midshipmen are highly edible and important food for many bigger critters. 


2. Luca Sartori, Summer Intern. 

Luca counting some of the 3,600+ Palaemon shrimp caught in June.  According to Luca, “It was a shrimptacular experience.”

Luca Sartori, our summer student intern.  For the first time, and in consideration of post and ongoing COVID restrictions, we invited a summer intern to join our trawling expeditions.  Luca is a sophomore studying oceanography at California State Maritime Academy.


3. Flatfishes.

Starry Flounder, Halibut, and a Shimofuri Goby, Alv1, 12 June 2022.

Starry Flounder. Ten baby starries were caught and released in June.  These tiny Starries probably hatched far upstream at the foot of freshwater creeks (primarily Coyote Creek) only a month ago judging from their lengths at around 35 to 75 mm.  Half were caught upstream at UCoy2 the rest were widely dispersed all the way out to LSB1.    


Right and left-eyed baby California Halibut at LSB1 on 12 June 2022.

California Halibut. Sixteen juvenile halibut were netted at downstream stations – thirteen of them at LSB2.  Young halibut arrive from the northern deep bay to feed in shallow waters of Lower South Bay. They are voracious ambush predators that feed on everything from amphipods to Anchovies. They migrate back out to deeper water in search of bigger prey as they grow.  Halibut are delicious!   

  • Halibut notes from Luca: California Halibut feed off anchovies and other small fishes by ambushing them. Like most flatfishes, larval forms have eyes on different sides of the head.  Eyes slowly migrate to one side as the fish develops early in life. 


4. Gulls.

California Gull Rookery at Adobe Creek, 17 June 2022.

California Gulls.  As noted in the previous Fish in the Bay – Anchovy Alert, we were mobbed by California Gulls at the end of June trawls.  Where do these gulls come from? 

  • At Luca’s suggestion, we investigated the gull rookery in Adobe Creek between Moffet Field and Palo Alto. Thousands of squawking California Gull adults were tending nearly adult-sized chicks when we visited.  This is a major gull rookery and quite a sight to see.  


Luca’s Gull notes:  California Gulls have been present in San Francisco Bay, but they were never abundant until fairly recently.  Their population surged in the early 1980s, when they seem to have discovered suitable breeding grounds close to ample feeding at nearby dumps and landfills. Today, there are 45,000 breeding gulls in the South San Francisco Bay.  Most of those are California Gulls. 

Fun fact.  The California Gull is the state bird of Utah!


Additional gull notes from Luca:

California and Western gulls are easy to confuse. They look similar and often inhabit the same area.  The easiest way to distinguish them is the legs. California gulls have yellow legs.  Western gulls have rosier pink legs. 

Subtle differences. 

  • Western Gulls are bigger birds. 
  • Westerns have lighter red rings around the eyes and lighter red dots on the bottom jaw compared to California Gulls. 
  • Western gulls also have a smaller pink gape at the corners of their mouths.  The gape is larger and redder in California gulls. 
  • California Gulls have a much wider range across North America and are often found inland.
  • Western Gulls rarely venture far from the coastline. 

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