Fish in the Bay – January 2019, UC Davis Trawls – Anchovy Spawn, a belated report.

Hi everyone.  The UC Davis/Hobbs Lab team was back again for March otter trawls in Lower South Bay this past weekend.  My official blog report will be out soon, pending completion of data analysis. 

In the meantime, this is a late report from a larval Longfin trawl conducted on January 19th.

Micah Bisson & Jim Hobbs on the research boat.   Dr. Hobbs is holding the skid-mounted Clarke-Bumpus net.  The larger hoop-shaped 20-mm net is behind him.

This was an abbreviated survey of only six stations to search for larval Longfins. The expedition included two rarely sampled stations far upstream in Alviso and Guadalupe Sloughs as indicated on the map above. 

A lot of “Young-of-Year” (YOY) and several “Year-Two” (Y2) Longfin Smelt were caught that day – almost all from the eastern side of Pond A21. Analysis of jars full of net contents is not yet complete, so I do not know the actual larval results.

However, I do not intend to discuss Longfin Smelt.  Instead, I want to examine indications of an earlier Anchovy spawn and some other environmental indicators that we witnessed that day.

Dorothy Anne.  We prepared to launch just as Dorothy Anne was pulling out for a day of trawling.  The Dorothy Anne is among the last remaining shrimping boats in SF Bay.  The owners of Laine’s Bait Shop in Alviso have been using her to catch shrimp and baitfish since the 1960s.

First trawl, Pond A21 borrow ditch, north side.

The 20-mm net targets fish roughly 20-mm long, albeit actual mesh size is 1.6mm. 

1. Highlights of the first catch. 

Aside from the young Lamprey, shown at the bottom of the tray, this is a fairly typical early winter catch: two Crangon shrimp, an American Shad, Top Smelt, some anchovies, silversides, and a Pacific Lamprey, among others. 

Some of the Native fishes:

Topsmelt.  Six Top Smelt were caught in Pond A21.  Young Topsmelt are closely related to Inland Silversides (both are of family Atherinidae). They look similar and compete with each other.  Non-native Inland Silversides usually seem to win the battle. 

Northern Anchovy.  Anchovies are primarily our late summer through early winter fish.  Anchovies become scarce here from around February through roughly April due to freshwater flushing.  And, as the Hobbs team has discovered since at least 2016, Anchovies must be spawning here!  The photo above shows one mature and three “Young-of-Year” (YOY) Anchovies.  

Larval flatfish.  This fish was too small to be identified in the field and was not recorded in the fish count.  In macro-photo we can see it is left-eyed, therefore most likely candidate species are Speckled Sanddab, Pacific Sanddab, or California Halibut.  Halibut like the warmth but don’t do well with the fresh water here, so I am inclined to guess this tiny fish was either Pacific Sanddab or Speckled Sanddab.

Pacific Lamprey.  I mentioned the Lamprey in an earlier post: “Parasite Paradise.”  Ecologically, the Lamprey may be the most important native indicator species in this display.  But, we almost never see Lampreys in otter net trawls because those slippery little suckers (literally a boneless sucker fish) easily outswim the net or slip through the larger mesh. 

Longfin Smelt.

The single “Young of Year” Longfin Smelt from the first catch.  By appearance, this fish looks mature and ready for spawning.  It has taken on the darker dorsal color indicating spawning readiness.  But, it has not yet grown to adult Year-Two” (Y2) length. 

Over the current spawning season, we saw numerous examples of Longfins seemingly too small to be a year old yet displaying sexually mature appearance.  It is not yet clear if these young Longfins actually participate in the seasonal spawn, so I will save discussion for another day. 

A Great Egret and two Snowy Egrets stalking tiny fish.

Reminder: Tiny fish are bird food.  As we counted our catch, some great and snowy egrets were foraging in adjacent marsh where we could not trawl.  Ideally, our trawl catch resembles what birds hunt in nearby rivulets, but you can never be certain.

Western Grebes in Coyote Creek.

Pairs of Clark’s or Western Grebes cruised in the deeper waters of Coyote Creek.  (The black hood extending down around the eye should indicate that these are Western Grebes, but I have a hard time telling the two apart.)

2. Anchovy Spawn!

Several Young-of-Year and juvenile Northern Anchovies from Pond A21.

It is well known that Anchovies spawn near coasts and in estuaries.  Anchovies at sea around the world tend to migrate coast-ward at spawning time.  However, Anchovy spawning in SF Bay, and particularly in Lower South Bay, is not well documented, if at all.   

As discussed in earlier posts, the “Brown-Back” Anchovy, the SF Bay native subspecies once described as “Engraulis mordax nanus,” must spawn in the Bay, but where and when?

  • See FISH BULLETIN No. 91, Common Ocean Fishes of the California Coast (1953), p.36: NORTHERN ANCHOVY Engraulis mordax Girard There are two recognized subspecies of this fish. One, Engraulis mordax mordax, is found along the entire coast. The other, Engraulis mordax nanus, is a smaller, brackish-water form found in San Francisco Bay. 
Juvenile Anchovy Close-up #1.

This photo shows portions of at least four juvenile anchovies draped over and around some Synidotea isopods and other debris.

BTW: I am referring to these baby anchovies as “Juvenile.”  They range from about 30 to 40 mm in length, but they are still skinny and have not developed a young adult body shape. 

Juvenile Anchovy Close-up #2: A juvenile anchovy draped over a larger Young-of-Year anchovy.  A Synidotea isopod is visible at lower right.
Juvenile Anchovy Close-up #3: The anchovy is at top and nearly wrapped around a tiny mysid shrimp.  Other mysids are piled up below.

How fast do Anchovies grow?  Growth rates and survival vary based on water temperature and food.  Various Anchovy studies from around the world indicate larval growth rates of 0.4 to a little over 1.0 mm per day.  If the same growth rates apply to San Francisco Bay Anchovies, then these little guys must be between six weeks to two months old.  Therefore, they may have hatched in late November or early December. 

  • Bay of Biscay, France and Spain: The growth rates calculated in this study are within the range of 0.4–1.0 mm day−1 (for larvae younger than 30 days) reported for this species in Mediterranean waters (García and Palomera, 1996; Dulčić, 1997; García et al., 2003; see also revision in Palomera et al., 2007).”
  • Off South Africa: “Growth was found to be rapid initially, fish attaining some 2 cm in the first 30 days, the rate then slowing down to about I cm per month, resulting in growth to 6.5 cm in the first 5 months. Growth then slows even further to c. 0.6 cm· month-I, and thus, after a year’s growth, the fish are of the order of II cm long.” 
  • ABSTRACT:  Anchovy growth rates – three annual cohorts – in the Adriatic Sea: The instantaneous growth rate, calculated for the whole fish sample, was 0.68 mm/day.”
Colorless baby anchovies.  Anchovy at bottom left is from station Coy4.  The other two, at top and right, were caught in Pond A21.

Are Dinoflagellates the key to local Anchovy recruitment?  Studies off the Coast of Southern California show that larval Anchovies depend on high concentrations of dinoflagellates within days after hatch.  Coincidentally, phytoplankton studies conducted by USGS and City of San Jose have also detected mid-winter dinoflagellate blooms that coincide with seasonal rains.

  • Lasker (1988):   “In common with other clupeoids the northern anchovy is highly fecund, and each female spawns from 20 to 30 times during a span of about 4 months, a spawning season which extends from December through April in California and Baja California coastal waters.  … Our laboratory studies on the anchovy always indicated that the only way we could insure survival of some of the larvae, usually a very small percentage, was to provide food at very high densities.  … food organisms of the right size and of the right density (20 to 30 particles/ml or more) were mostly dinoflagellates and were generally located in stratified layers near the chlorophyll maximum. Twenty to thirty particles per milliliter seemed to be a threshold quantity needed for successful first feeding.”  (pp.29-30)
  • Lasker (1981):  “Upwelling brings nutrients to the surface and results in high levels of primary productivity in the surface layers of the sea and particularly in water adjacent to the shore. This is a common course of events in the Southern California Bight but enhanced productivity does not necessarily ensure good larval fish feeding conditions despite the fact that above-threshold-for feeding concentrations of particles, usually a variety of diatoms, are prevalent during these events. Behaviorally, the anchovy larva ignores or rejects diatoms, probably because diatoms are spiny and filamentous. These phytoplankters are rarely found in the anchovy larva’s intestinal contents (Arthur, 1976; Berner, 1959; Scura and Jerde, 1977).”  (P.377) 
Young of Year blue-back?  From outward appearance, this young anchovy could easily be mistaken for as a brown-back.  Closer inspection reveals blue pigmentation.

Studies in other parts of the world have found that anchovy growth and recruitment success are highly dependent on where ocean currents disperse the larvae to inshore locations or farther out to sea.

  • A summary of work presented at University of the Basque Country (UPV/EHU) correlates later anchovy migration in the Bay of Biscay with growth rates:  “The chemical analysis of the otoliths indicated that the anchovies belonging to the first group grow much more rapidly (0.88 mm a day) than the second group (0.32 mm a day).  … the results show that individuals that swim out to sea and then return make up 99 percent of the population of young anchovies.  Thus, it is suggested that this movement of young anchovies to the exterior zone of the estuary is important to successful recruitment.” 
  • Falcini, et al. (2015) describes a similar role of ocean upwelling and currents in dispersing larval anchovies and eggs off the southern coast of Sicily: 
Juvenile Anchovy from Coyote Creek.  The first trace of blue-back pigment is showing just behind the eye.
Another young Anchovy from Station Coy4.

In every instance I could see, young anchovies longer than roughly 40 mm showed blue or green pigmentation on the head.  All larger anchovies showed clear signs of blue or green dorsal color.

Where have native Brown-Back Anchovies gone? I would be delighted to report that these juvenile anchovies are members of the local “Engraulis mordax nanus” variety.  Unfortunately, closer examination does not support that hypothesis.  All larger juvenile anchovies caught on January 19th appeared to show nascent green-back or blue-back pigment. 

Anchovy adults.  These two appear to be faded ocean-going blue-backs, though they also showed some signs of green.

Even amongst adult anchovies, all appear to be ocean-migrating blue-backs or green-backs.  This contrasts with our observations of numerous adult brown-back anchovies up until late-2016. 

These two adults were a little greener at the head.  Dark melanophores continue to make the dorsal side look dark even as all other signs of color had faded.
Young of year anchovies showing green (at left) or blue-green (center and right) color.
Young-of-Year anchovies showing early signs of vivid blue color.
More blue, green, and blue-green anchovies.
Four more anchovies from Coy4.  The youngest of this group show tiny patches of green on the head.  The larger ones show strong signs of blue-green color.

It is good to see signs of spawning anchovies in the vicinity of Lower Coyote Creek and restored ponds.  But, why do they all appear to be blue and green-backs?  Why do we see no Brown-Backs amongst this spawn?

Why we should we care about anchovies: 

3. Shrimp Spawn!

A large pile of Crangon were caught a Station Coy2, just downstream of the railroad bridge on January 19th.

Crangon Shrimp (Crangon franciscorum). We were near the tail-end of the Great Crangon Brooding Migration of 2018-19, albeit, we continued to see a few egg-bearing Crangon stragglers into early March. 

The Crangon winter brooding cycle was not obvious in our Lower South Bay observations from 2015-2017.  Crangon numbers were very low here during those dry years.  From what we observed this year, it is now clear that female Crangon swim upstream into Lower Coyote Creek to release larvae from eggs when water temperature drops in winter.  After larvae release, females retreat back to the deeper Bay before winter flushing.  

(Also note:  Longer-term SF Bay shrimp data is maintained by Kathy Hieb and CDFG’s San Francisco Bay Study and the Interagency Ecological Program for San Francisco Estuary )

It is well documented that Crangon populations boom after a succession of wet winters.  As such, the Crangon cycle is a good overall indicator of ecological health in Lower South Bay.

Palaemon macrodactylus.

Palaemon Shrimp.  Some non-native Palaemon shrimp are getting a little redder and larger as is typical this time of year.  Apparently, females start developing larger Chelae (forearms, or legs with pincers) as they grow ready for egg development.  I believe female Palaemon use these Chelated arms for turf-battle fights over brooding space once they become laden with eggs. This in addition to pincer use for feeding and grooming.

(Male Palaemon may develop large chelae as well.  I only know for certain that egg-bearing females here often have a reddish hue and always seem to have enhanced chelae that are not so conspicuous at other times of year.)

4. Upstream stations: A different freshwater world.

Micah Bisson sorting and measuring sticklebacks and bugs on Guadalupe Slough.
Guadalupe Slough Sticklebacks.

Unsurprisingly, a very different array of critters was caught in the fresher, far upstream stations. 

  • Insects like Water Boatmen and Dragonfly nymphs are common in freshwater marsh. 
  • Three-spined Sticklebacks are voracious fish egg and larva-eating demons. Several caught in Guadalupe Slough were pregnant or “spent” females.
  • At the “freshwater-salt wedge” we caught gobs of mysids that later appeared to proliferate at downstream stations as well (See February Fish in the Bay reports.)

Interestingly, I just learned that Water Boatmen insects (aka: Corixidae) are some of the loudest organisms in the world, at least on a pound-for-pound basis.  If you hear crickets chirping in freshwater marsh, the sound may actually be coming from Water Boatmen:   


Upstream at Alviso in the afternoon.  By the time we finished the last larval trawl at Alviso, the Dorothy Ann had returned to port.  She was tied up aft of the Dragon Lady, one of the other last remaining commercial shrimp boat in SF Bay.  

Probably not coincidentally: dozens, possibly a few hundred, goldeneye and bufflehead ducks typically concentrate where freshwater meets the Bay.  These are diving ducks that feed off the bottom.  I suspect these ducks loiter here because of abundant food.  But, also keep in mind that hunting is not allowed here, and ducks figure out the safe zones pretty quickly.

Two White Sturgeon.

Lucky day at Alviso Dock.  We returned to the Alviso Dock just as one of the CDFW wardens was measuring two White Sturgeon caught by some weekend fishers.  Wow!  Look at the size of those two prehistoric monster sturgeon!  Dr. Hobbs estimated that each of those two fish may be 30 to 35 years old! 

It is a wonder that so many sturgeon are caught in this area.  … That is to say, I wonder if these giant fish are getting fished out?!?!

Jim Hobbs showing off some of our larval catch – packed with mysids.

Stand by for the March report!

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