Fish in the Bay – July 2024, Part 2. Anchovy Colors & Spawning Behavior.

This second part of the July report covers some additional random items.

• Spawning Anchovy sex ratio
• Water Color Update for red tide season
• Anchovy colors in July.

1. Spawning Anchovy Sex Ratio.

We may have inadvertently detected skews in Anchovy sex ratios: female Anchovies appear to have a strong preference to hang out in restored Ponds A19 and A21.  This female skew may also extend into the upstream sloughs as well based on limited data from both July and August trawls.

• The map image above highlights a few stations where differing sex ratios were most conspicuous.
• The tables at the bottom and right edges summarize Anchovy data for both July and August.
• Important caveat: Male and female Anchovies look the same. We determine sex strictly from “egg-checks” in which each Anchovy expresses either 1) eggs, 2) milt, or 3) nothing. This is not a fool-proof method, but it is non-invasive and hence non-lethal for Anchovies. …
• At least 2/3rds of all Anchovies in restored ponds expressed eggs in both July and August.  That’s fairly solid confirmation of a serious sex skew.   

An Anchovy egg-check in Pond A21.

We have closely monitored the summertime Anchovy spawn each summer since 2020. In addition to counting and measuring, we conduct limited “egg-checks” on a few individuals at each station to track the geographic spread of spawning-ready individuals. – Most Anchovies are also photographed for subsequent dorsal color evaluation.    

2. Water Color Assessments Continue.

The warm months of late summer are H. akashiwo / Red Tide season.  H. akashiwo was the flagellated single-celled organism that bloomed into a massive fish-killing red tide in central SF Bay in August 2022.  Somehow, we dodged that bullet here in Lower South Bay (LSB).  But, H. akashiwo is always present in low numbers or as sleeping cysts.  The characteristic reddish-dark brown stain of a toxic bloom could appear at any time when warm waters, high stratification, and intense sunlight combine into ‘perfect storm’ conditions for the organism.  

We continue monthly evaluation of water colors using the UCSC Kudela Ocean Sciences Lab color chart:  http://oceandatacenter.ucsc.edu/PhytoBlog/wharf water color/SWchart_caption.pdf   

• In the photo montage shown above, my thumb points to the best match with water color as viewed from both sunny and shady sides of the boat.

In July 2024, water colors ranged from Different Gold (#24) to Melange Green (#26).  This is typical for a New Moon / Spring Tide. 

• Gravitational Shadow of the Moon: In this shallow part of the Bay, waters tend to ‘brown-down when sediment resuspension is high.  Waters generally ‘green up’ during Quarter Moon / Neap Tide periods. 

3. Interesting coincidence.

Prymnesium parvum cultures from the Oder River. | © Katrin Preuss/IGB

In August 2022, San Francisco Bay experienced it’s biggest fish-killing red tide bloom of the century caused by a mixotrophic flagellated alga – H.akashiwo.  At the same time on the other side of the world, a mixotrophic and flagellated Haptophyte, Pyrmnesium parvum, caused nearly identical ecological destruction.  

YouTube Video:  Discovery of the Largest Protein Ever, In the Most Unlikely of Organisms (PKZILLA)  https://www.youtube.com/watch?v=BZ1cwtNoPCo 

• Oder River disaster: What is known about the alga Prymnesium parvum? https://www.igb-berlin.de/en/news/oder-river-disaster-what-known-about-alga-prymnesium-parvum 
  • “In July and August 2022, a man-made environmental disaster occurred in the Oder River: a mass die-off of fish, mussels and snails that started in the Polish section of the Oder and then continued downstream until it reached the border Oder. Researchers estimate that up to 1,000 tonnes of fish were lost. The immediate cause of their death was a toxin-producing (planktonic) brackish water alga, scientifically known as Prymnesium parvum …
    • Prymnesium parvum is a unicellular microalga that is 5 to 10 micrometres (µm) long and 4 to 7 µm wide. 
    • Using its two flagella of equal length, the alga can actively move through  It also has a holding organ, the so-called haptonema, with which it can attach itself to prey organisms and other surfaces.” 
  • Fallon et al. (2024) Giant polyketide synthase enzymes in the biosynthesis of giant marine polyether https://www.science.org/doi/10.1126/science.ado3290 
    • “Prymnesium parvum are harmful haptophyte algae that cause massive environmental fish kills. Their polyketide polyether toxins, the prymnesins, are among the largest nonpolymeric compounds in nature and have biosynthetic origins that have remained enigmatic for more than 40 years. …
    • These molecules often require large—sometimes massive—enzymes or enzyme complexes for their biosynthesis. Fallon et al. identified genes from a toxic microalga corresponding to polyketide synthase megaenzymes that are among the largest proteins identified to date, one being nearly 5 megadaltons.”

Tiny organisms provoke us to make the most interesting discoveries!

4. Anchovy Color Assessments.

We have qualitatively observed Anchovy (and other Clupeiform fish) dorsal colors for several years now.  I had briefly experimented with “Pantone” and other color scales in attempts to quantify the salinity-induced color changes we see, but I never pursued it.

• During August trawls, UC Davis intern, Mia Thuilot, suggested we use the Kudela Lab Color Chart to evaluate Anchovies. This was a brilliant suggestion. … Albeit, some modifications were needed. The Kudela Lab Color Chart incorporates way too many colors – 32.  And, the numeric arrangement of colors is a bit chaotic.    
• Accordingly, I honed down the 32-color Kudela Lab Chart to a smaller selection of 13 colors – and rearranged them into an order that best matches the Clupeiform rainbow of colors. This simplified color scheme seems to work!

As discussed various times in the past, plate-like guanine crystals in chromatophore cells diffract sunlight into bright iridescent colors we see along the backs of Clupeiform fishes.

• This blog post from 2018 provides some background regarding Anchovy colors. https://www.ogfishlab.com/2018/11/10/fish-in-the-bay-11-nov-2018-uc-davis-trawls-anchovy-color-hypothesis/
• Another blog post form 2020 discussed salinity-induced color change in Shad: https://www.ogfishlab.com/2020/12/13/fish-in-the-bay-december-2020-anchovy-rebound-blue-fish/

The major caveat for Anchovies:  Unlike other Clupeiform fishes, Anchovies lose guanine crystals in low salinity.  Anchovy dorsums become translucent and colorless as guanine drains away from chromatophore cells.

• For this reason, the additional qualitative five-point scoring system shown above is proposed.

The remainder of this report tests these color and chromatophore scoring systems against Anchovies caught in July.   

5. Anchovy Color Assessments in July.

Artesian Slough.  We started the July trawling weekend on the upstream side. Artesian Slough stations were trawled first.  Out of six Anchovies caught, only one at station Art3 expressed eggs and not all were checked. 

Color Assessment: 

• The Anchovy at far-left has at least 50% chromatophore sparkles across the dorsum expressing “Different Gold (#3).
• The next two Anchovies just to the right look golden at first glance, but they are actually clear / colorless. (One has a tiny, near negligible, trace of green sparkles near the head.)
• The three Anchovies to the right also have at least 50% chromatophore sparkles (maybe 80 to 90 percent). There colors are closest to Lounge Green (#7) or Nurture Green (#6)  

Pond A19.  At this point in July, we were not yet aware that Anchovies might segregate by sex. Only a few fish were checked.  They were all female. 

Color Assessment:  Most Anchovies expressed close to the same color = Green Bay (#13). Anchovies also showed substantially full chromatophore coverage with scores between 2 to 4.

Upstream stations – Dump Slough & Upper Coyote.  Again, only a few fish were checked at each station.  Seven out of sixteen were positively confirmed to be female.

Color Assessment:  Natural Green (#6) or no color (no guanine crystals) at all. 

Downstream Stations – Alviso Slough.  Only a few of the 48 Anchovies caught in Alviso Slough were checked – three were confirmed female. – At station Coy4, we detected 2 females and our first male Anchovy expressing milt. 

Color Assessment at Coy4:  All Anchovies had low Chromatophore Scores = 0 to 2.

• Anchovies with crystals (mainly along their lateral lines) expressed Bosphorus (#12) or Jadite (#8)

LSB Stations in July – At LSB, we realized we were seeing more male Anchovies than we had seen at any other point in the July weekend.  Something interesting was happening!   We performed more extensive egg-checks.  The more we checked, the more males we found!

Color Assessment at LSB1:  Three of four Anchovies shown above are Bosphorus Blue (#12). This is consistent with higher salinity at around 25 ppt.  The bottom Anchovy with very little color only shows Jadite Green (#8). The other three also show varying traces of Jadite.

Now halfway through our second day of July trawls, we developed a working hypothesis: female Anchovies concentrate in restored pond and upstream locations in Lower South SF Bay.

• From that point on, we conducted 100% egg-checks to test this hypothesis. Results:  Anchovies in Pond A21 were overwhelmingly female!

Color Assessment in Pond A21:  A rainbow of Anchovy colors from Bosphorus Blue (#12) to Jadite Green (#8).  Some, presumably younger Anchovies, showed no color (no guanine crystals) at all.

Anchovies at Pond A21-4: Again, Anchovies were overwhelmingly female with colors ranging from Bosphorus blue to Jadite green – or no color at all.

The last two stations trawled in July were Coy2 and Coy3 in the main stem of lower Coyote Creek.  100 percent egg-checks were performed. 

• It appears that males outnumbered females at these stations – at least in July.

Results at station Coy3:  Again, males outnumbered females – by a small margin.

Why would Anchovies segregate by sex?  – This is an opinion … just a guess. 

According to papers published by Reuben Lasker in the 1980s, female Anchovies must consume each day roughly 4% of their bodyweight in protein to support egg production.

• Females may be more willing to sacrifice thermal and osmotic stress in exchange for a protein-rich zooplankton diet.
• Males and young may be satisfied to linger in cooler saltier waters downstream and/or in the main stem of Coyote Creek.
• Investigation continues!

Yusuf / Cat Stevens – Moonshadow (Live, 1971) https://www.youtube.com/watch?v=AopGsKIKMp8