Fish in the Bay – 12-13 May 2018 UC Davis Trawls – Crangon Time!

Hello, fish and bug enthusiasts.  I rode with UC Davis fish researchers last month on Saturday, May 12th.

I continued to include counts of jellies, comb jellies philene/snot-ball snails at the bottom of the tables.

Good news:  1) The winter comb jelly attack is officially over.  2) This appears to be a very good year for native crangon shrimp – so far.

Bad news?  We continue to see a hot pocket of non-native philene/snotballs at stations LSB1 & LSB2.  This is probably a permanent condition.  But, other than being disgusting to look at, I can’t discern particular harm they cause.  It would be good news if philenes ate non-native corbula clams, but alas, corbulas colonize the mouths of creeks and rivers, i.e: Alviso Slough, Artesian Slough, and the upstream segments of Lower Coyote Creek.  As near as I can tell, philenes never meet corbula.

Saturday, 12 May – Bay-side trawls

Sunday, 13 May – upstream and east of Railroad Bridge

Fewer fish in May.  The tables show slightly less than 600 fish for the May weekend compared to over 2,000 in April.  The numbers drop is mainly attributable to all the juvenile Staghorn Sculpin caught in April – 1,246 of them, if you recall.  Sculpin are still present, but population boom appears to be over.  Young sculpin have dispersed.

Baby fish month didn’t happen?  Usually, April is the month we see at least a few thousand “Unidentified Gobies.”  Baby fish made previous April trawls a bit tedious and slow as we all grabbed trays to count the larval horde.  Last year, the Hobbs team counted 2394 tiny unidentified gobies on the April weekend.  This year was notably different: aside from young sculpin, very few baby fish!  I thought Baby Fish Month might arrive in May, but it didn’t.

Two of the 51 “unidentified gobies” seen on 13 May.

In a perverse way, this might be a good thing.  Jim Hobbs always presumed that most of the larval unidentified gobies were invasive yellowfins.  And, high counts of adult yellowfin gobies later in the years corroborated this assumption.  This year, we did not experience a true “Baby Fish Month.”  Instead, we saw a Staghorn Sculpin population explosion the likes of which has not been detected since, possibly, 2012.  Did sculpin break the back of a six-year yellowfin hegemony?

We think this latest pair of wet years helped recruit the sculpins.  Maybe, Yellowfin Gobies don’t do so well in a fresher and more variable environment.  Or maybe, young sculpin eat yellowfin eggs and larva like starving piranhas.  All we can say for sure is native sculpin are up, and non-native yellowfins continue to be down.

Above, Dr. Hobbs sports a new Captain’s hat as he sacrifices a sprinkle donut to the sea gods and goddesses. 

Emily Trites stood by on water quality monitoring instruments as we launched. 

Dr. Levi Lewis manned the net.  (Rain gear was for sun protection on this near cloudless day.) 

Mossy Bryozoan.  Few fish were caught at the first station in Alviso Slough near the Alviso Launch.  But, the net pulled up several chunks of mossy bryozoan.  I think of bryozoans as San Francisco Bay corals.  They are colonial animals that build structures out or chitin or protein material and filter-feed on microscopic prey.  We see these animal colonies frequently, but it is hard to quantify and document them.  Was this a single bryozoan colony in my hand, or one of several fragments?  There could easily be several thousand individual “zooids” (the tiny animals that comprise the bryozoan colony) in this single piece.  They must be important filter feeders in this system.

Corophium.  The several mossy bryozoan colonies caught at Alv1 station were peppered with corophium.  Both corophium and mossy bryozoan appear to concentrate in the Alviso, Artesian and Coyote Creek tributary channels where freshwater meets the salt (same locations as corbula).  Albeit, mossy bryozoans also seem to find a nitch along channel edges out in Lower South Bay as well.  These all seem to be good filter-feeding locations with strong creek and tide currents sweeping material by.

Corophium dwell in mud tubes.  Here they were found enmeshed in mossy bryozoan.  Were corophium feeding on bryozoan zooids?  Or, perhaps they were stealing food from zooids?  Or maybe, corophium simply got tangled up in bryozoan mossyness as the otter trawl net scooped up several hundred feet of muddy bottom!  In any case, corophium are very important bugs.  Many types of fish and shore birds hunt them.

Staghorn Sculpin were caught further downstream in Alviso Slough.  These sculpin are still not quite adult-size, but they are getting bigger.  Last month they were all tiny babies.

More about Corophium.  The amphipod count (corophium) dropped from over 1,000 at station Alv1, to less than 50 at Alv2, and then to zero at Alv3.  Are growing sculpin and anchovies eating all the corophium downstream of station Alv1?  Or, does varying salinity simply defining the boundaries of respective habitats?  Literature states that corophium should be quite happy at higher salinity, so it is not a stretch to speculate that hungry fish are controlling the bug population at downstream sites.  Our particular species tends to be Corophium spinicorne, but there are many types of corophium in estuaries around the world.  They are important food for steelhead, sculpin, flounder, sole, even longfin smelt and crangon shrimp.  It seems almost everything eats this little mudflat and channel dweller.  After mysid shrimp, corophium could be our most important bug.

• One study of corophium as salmon food in Washington state: http://www.dtic.mil/dtic/tr/fulltext/u2/a113215.pdf
• Another study of corophium salinity tolerance in the Baltic here: http://www.iopan.gda.pl/oceanologia/OC_37/OC37_1-7_Dobrzycka.pdf

Northern Anchovies were caught still further downstream, in the Bay, and in restored salt ponds.  Both types of anchovy were caught: local brownbacks and sea-going greenbacks.  The different colorations are easily identifiable.  Far out in the middle of Lower South Bay (LSB1 and LSB2 stations), we saw only greenbacks.  But at all other stations in Coyote Creek and Pond A21 both types of anchovies seem to mingle a good deal.  The greenest greenbacks and brownest brownbacks shown above were caught in Pond A21.  For all I know, they may interbreed.  Or, perhaps some change color as they mature?

From Jim Hobbs I learned long ago that the brown versus green anchovy phenomenon was first documented by biologist Carl Hubbs in 1925.  (Actually, Hubbs described our Bay anchovies as pale or gray.  “Brownback” is the Jim Hobbs description.)  Hubb’s paper is available on line in newer snazzy format here: http://www.oac.cdlib.org/view?docId=kt6c6004pk&brand=oac4&doc.view=entire_text   You can read on pages 18-20 where Hubbs summarizes observations from 1925:

“The outstanding result of our study of the variation in the California anchovy is the demonstration of the existence in the brackish waters of San Francisco Bay of a very distinct race, analogous to the Baltic race of herring (Heincke, 1898). This form is so sharply differentiated from the ocean anchovy that it may be separated from it as a distinct subspecies, for which the name Engraulis mordax nanus Girard is available.^[6] …

Before the breeding season, … large schools [of ocean-going greenbacks] appear at the surface off the Golden Gate, the entrance to San Francisco harbor. Soon after, they enter the bay, in fewer or larger numbers, depending on unknown causes. So far as could be determined, however, they do not penetrate far into the bay, and according to intelligent fishermen, they retreat into the ocean when the streams tributary to the bay are in flood.”

In our modern times, the UC Davis crew regularly catches ocean-going greenbacks all the way into Lower Coyote Creek.  This did not happen when Hubbs wrote his paper.  Something clearly changed in Anchovy-world since 1925.

I prefer ocean-going greenback anchovies for their color.  But, brownbacks are our San Francisco Bay native: a unique subspecies in the Bay.

This one larval anchovy was caught at station LSB1.  (I photographed it alongside the only Pacific Herring seen during the May trawls.)   The Hobbs team has verified on numerous occasions that Northern Anchovies successfully spawn in Lower South Bay.  This little larva is just one of the more poignant pieces of evidence.

Crangon.  The biggest May surprise was high tally of native crangon shrimp.  These were mostly Crangon franciscorum (AKA: Bay shrimp or grass shrimp).  But, there were a fair number of black-tailed crangon (Crangon nigricauda) in the mix.  According to various papers, the range of the two crangon species overlap in SF Bay with C. franciscorum far outnumbering the black-tails.  C. franciscorum tends to inhabit brackish to fresh shallows.  C. nigricauda prefers saltier and cooler territory.  However, UC Davis trawls don’t seem to distinguish any habitat gradiation between regular Crangon and black-tails.  This may also be due to the rough nature of otter trawling.

Above, C. franciscorum flanked on either side by C. nigricauda (black-tails)

Sometimes, it is very obvious which Crangon are black-tails and which are franciscorum.  But, I have mentioned before, it can get difficult to impossible to distinguish the two, especially when you have a pile of a thousand or more to sort and count.  In any case, it is good to see that crangon are back.

Palaemon shrimp.  Crangons compete with non-native Palaemon and Exopalaemon shrimp.  (AKA: Oriental shrimp and Siberian prawn respectively.)  Palaemon shrimp outnumbered Crangon during dry years.  In addition to a steak knife rostrum, palaemons have a brownish to pinkish color.  Larger adults seem to turn near tomato-red to my untrained eye around January.  Until now, I thought that higher salinity favors palaemon shrimp over crangon.  Apparently the issue is more complex.

Exopalaemon shrimp.  The “exos” are always bit players of the shrimp world in Lower South Bay.  They are always found in slightly fresher, slightly more upstream locations.  One would think that a pair of wetter years would lead to an exopalaemon population explosion.  Wrong again!  … It’s more complex than that.  Crangon numbers and locations suggest there may be a good deal of intra-shrimp competition going on.

Jellyfish invasion!  Seven unknown jellies were caught at the LSB stations in May.  Based on this photo, I tentatively identify two of the seven as Pacific Sea Nettles (PSN).  In April, the Hobbs team caught 25 jellies at the same stations (At least one of those was a PSN).  Like comb jellies, the medusa-type jelly invasion seems to be a cool ocean water induced phenomenon with numbers tapering off as Bay water temperatures rise.

• It is interesting that ocean beaches near San Francisco also had a Moon Jelly invasion over the past month: https://www.nbcbayarea.com/news/local/Countless-Jellyfish-Wash-Ashore-at-Pacifica-Beach-in-San-Francisco-483994971.html
• A moon jelly invasion also occurred in 2010 (Both instances happened two or three years post-El Nino. … with drop in ocean temperatures? – coincidence? Hmmmm ….) https://www.sfgate.com/bayarea/article/S-F-Thousands-of-dead-jellyfish-on-Ocean-Beach-3245794.php

More weird critters at LSB stations.  Exotic animals inhabit the middle of Lower South Bay.  In this instance, it was a mix of benthic gobies, mollusks, and tunicates.  Many of the revolting philene/snotball snails are shown here.

A collage of invertebrates from station LSB2.  These were some of the interesting bottom invertebrates.  All of them are fairly common and all non-native.  Japanese Littleneck Clams are very edible and desirable – in Japan.  Atlantic Oyster Drills are a particular menace to oysters and other bivalves everywhere.  Encrusting Bryozoa form a hard coral-like surface over old shell deposits.  They don’t remotely resemble their mossy bryozoan cousins.

English Sole – continued evidence of a cool ocean!  Eleven more young English sole were caught in May (three shown in photo above).  A total of 248 English sole have been caught since January.  This compares to ZERO English sole for at least two, maybe four, previous years.  Dr. Hobbs clued me in to the idea that English sole recruitment is affected by cool ocean upwelling.  This is an odd fish.  Adults spawn offshore.  Larval sole are obliged to drift or swim into estuarine nursery habitat.  From what I glean, survival of larva is highly dependent on a temporary lull (?) in ocean upwelling coupled with cool ocean temperatures. If ocean temperatures are above an ideal range, tiny larvae grow too fast and don’t make it to nursery habitat in time – most die.  But, there is also much unknown complexity to how baby Sole find their way to a protective nursery.  https://swfsc.noaa.gov/publications/CR/1987/8710.PDF

This seems like a very chancy way to propagate a species.  Both sole and jellies seem to be connected to keywords “cool” and “upwelling.”  It makes me wonder if we could eventually predict timing and abundance of these different species based on local ocean temperature, winds, and currents.  … OR, flip this notion upside down:  Maybe we could learn to monitor local ocean conditions based on observed fish populations?

California Halibut like it warm and salty.  This was the only halibut caught in May; one of only two since January.  Halibut numbers have been low since 2016.  Dry and El Nino years seemed to be good for halibut.  We see fewer of them now.  But, to complicate matters … halibut eat anchovies (amongst other small fish).  Recent wetter winters appeared to have reduced local anchovy numbers, until these last two months, and reduction in food may have impacted halibut as well.

California Tonguefish. This is a native flatfish.  Tonguefish are not rare, but they are strange looking. We had not seen these for a few years, then two were caught in May.

Two Shimofuri Gobies, one Shokihazi.  I took this photo mainly because Jim Hobbs told me that the two striped fish are female or juvenile Shimofuris.  This perplexed me because I have seen many shimofuris, but they always looked fairly homogeneous greenish-gray in color.  Levi later confirmed to me that Shimofuri females and young have longitudinal stripes, like chameleon gobies.  In fact, many shimofuri and chameleon gobies can be indistinguishable without lab analysis.  All three gobies, shimofuri, chameleon, and shokihazi, are non-native and invasive.  But, they are usually far outnumbered by non-native and much more invasive Yellowfin Gobies.

Bat Rays.  A baby bat ray was netted at station LSB2. The four yellow bugs are synidotea (isopods).  You can also see three crangon on and beside the bat ray.

Jim Hobbs shows off the larger bat ray caught at station Coy4.  Two thumbs up!

American Shad.  We returned to Pond A21 and Lower Coyote Creek later in the day.  These were some of the 46 American Shad caught over the May weekend.  You can also see many tiny mysids swimming around them.  As always, shad are non-native, but we like them.  They even pose nicely for photos!  It is very hard to not like this fish.

Shiner Surfperch.  This was the only native surfperch caught in May.  This one is only a few days old, judging from the size.  Only three have been encountered in the Alviso Marsh Complex so far in 2018.

Striped Bass.  As always, stripers were present: three on Saturday and 34 more on Sunday. Amongst the fish seen on the May weekend, striped bass should show signs of stress from low Dissolved Oxygen (DO).   I highlighted in red low DO readings at the top of each table – far above.  DO was lowest at UCOY1 station at 3.1 mg/l on Sunday, and yet eleven striped bass were caught there.  This is a tough fish.

Bay Pipefish.  This pipefish was in Pond A21.  Now that I look at it, I wish I had examined his pouch.  He probably was a male full of baby pipefish.  He was promptly returned to the pond with my curiosity unsated.

Copepods.  The UC Davis researchers deployed mysid and Clarke-Bumpus nets during the afternoon ride home.  As usual, lots of tiny bugs were captured.  Above, I am showing some copepods and microscopic larval shrimp on the side of the collection jar.  It is a reminder that most life on Earth is extremely small.  (A long time ago, I read that all the copepods in the world’s oceans, lakes, and rivers, outweigh all other multicellular animals by a factor of 10!!!!)  Giants like us and the fish can’t survive without the small stuff!

That’s all for now folks!