Fish in the Bay – December 2024. Happy Longfin New Year!

Happy New Year!  This post mainly focuses on the latest return migration of spawning Longfin Smelt – a now an officially designated endangered species as explained in this article by Alastair Bland: https://mavensnotebook.com/2024/12/10/notebook-feature-the-longfin-smelt-joins-the-celebrated-ranks-of-the-federal-esa-but-can-it-recover/?doing_wp_cron=1734063855.2761249542236328125000 

• As far as we know, Longfin Smelt probably returned to spawn in Lower South Bay Marshes since the San Francisco Estuary formed at end of the last Ice Age glaciation.
• But life in this highly urbanized estuary was disrupted after the mid-1900s.  Dr. Jim Hobbs and UC Davis researchers searched and failed to find any evidence of Longfin Spawning in this area from 2010 to 2017.
• Beyond our wildest dreams. A few baby Longfins showed up in trawl results in spring 2017. The following year gravid females were documented.  Longfin numbers increased all years since.     

Cool temperatures and rainwater flushing signal upstream migration for Shad and Herring as well.  Shad numbers (both American and Threadfin Shad) have also increased since 2017, albeit sporadically. 

Other winter migrations: 

• One English Sole and three Speckled Sanddabs showed up in December. Winter is recruitment feeding time for these baby flatfishes.
• A few large female Sculpin and Yellowfin Gobies laden with eggs were also caught and released. Their spawning time also begins over the next month or two.

1. Longfin Smelt.

Sami Araya shows us how angular shaped anal fins identify these two Longfins as female.

Longfin Smelt count = 268.  Longfins returned in greater numbers in December!  This was our second highest December count on record! (The record December count was 498 in 2022; next highest was 204 in 2023.)     

Sami measures Longfins.  Jim Hobbs records data.

Sami noted a dramatic mix of very large adult Longfins (100+ mm) along with many younger/smaller individuals. These results indicate that some members of the LSB population are surviving well into adulthood, perhaps even into their third year!

As we have come to expect since 2019, the largest adult males are caught at upstream stations.  Males seek a spot where cool (10 to 12 degree C) fresher water (0.5 to 10 ppt) flows.  There they find any piece of hard substrate where a female can lay her sticky eggs.  Rock, shell, sand, or plant stems will suffice.  Males use their long anal fins to sweep the spot clean.    

Restored ponds A19 and A20 are populated mainly with juvenile and female Longfins.  Water moves slower in the ponds.  Production of microscopic food is high. The restored ponds appear to be resting and refueling stops on the way to upstream spawning grounds.

To the best of our knowledge, the biggest and strongest males brave a life ending one-time trip to upstream spawning grounds. 

• Males cease eating as they defend prime mating places in hopes that females will find them.
• Their dorsal sides darken as they waste away from December until around March.    

December surprise: We normally don’t expect to catch many mature females at the farthest upstream UCoy1 spawning station.  Females don’t loiter long here. These females may be telling us that active spawning has already begun!

Five Longfin Kings were also caught here.  Sizes were 98, 99, 100, 107, and 116 mm … in addition to almost another dozen smaller fishes. 

Female Longfins stage in downstream marshes where both salinity and food production are higher (e.g. in the restored ponds).  They need zooplankton protein to support egg production.    

• UC Davis researchers believe that females may make repeat egg delivery trips to upstream spawning sites. Females may even survive to spawn in successive years! – as evidenced by some of the jumbo-sized females we are seeing now.

2. Showy Snailfish – a fish with hands!

Showy Snailfish.  When we caught this fish at station Coy2, Sami, Brian, and I were stumped.  Jim Hobbs had seen one once 10 years earlier (– at station Coy4 on 3/15/2014).  He immediately identified the fish and told us its story.

• Some Snailfishes are the most common fishes in the deepest oceans and under sea ice in Antarctica.
• They have suction discs on their chests, similar but different from sucker discs on gobiids.

Close examination revealed that this fish has tiny arms and hands!  The first several rays of his pectoral fins have fused into arm-like and finger-like appendages! 

I had already learned from Bruce Herbold’s Facebook posts that Sea Robbins (in the family of scorpion fishes) also evolved similar hand-like appendages.

I took many pictures before release … because you never know.   We may never see another Snailfish again!

Additional fun facts from Wikipedia:

• Snailfishes make up the Liparidae, which is classified within the order of Scorpaeniformes.
• Snailfish are benthic fish with pelvic fins modified to form an adhesive disc.
• In some species, such as the Antarctic Paraliparis devriesi, the pectoral fins include a taste bud.
• Snailfish are found in oceans worldwide, ranging from shallow intertidal zones to depths of more than 8,300 m (27,200 ft).   

3. Staghorn Sculpin – not doing as well in 2024.

Staghorn Sculpin count = 7.  The final 2024 Staghorn count was 194 – the worst year on record.   

• Staghorns are a confirmed “La Nina fish” in literature. The strong, but short, El Nino of 2023-24 likely hammered them.

It was interesting to compare this Staghorn with the Snailfish caught at the same station.  – Fishes usually lack complex appendages aside from fins.  But, when extra feelers, tasters, or defensive antlers proved useful, Staghorns and Snailfishes adapted existing body parts into new structures. 

A horde of Ducks fly over Coyote Creek as we exit Artesian Slough on December 1^st.

The Moody Blues – Your Wildest Dreams  https://www.youtube.com/watch?v=5yYn_rGHSIc

• The video depicts a human “lost love” story of some sort.  Do Longfin Smelt feel similar emotions?
• Octopuses changing skin pattern while asleep may show they dream … https://www.theguardian.com/global/2023/jun/28/octopuses-changing-skin-pattern-while-asleep-may-show-they-dream-research-shows
• Do fishes dream?