Fish in the Bay – May 2025, WRMP Eden Landing Survey #2

The UC Davis OGFL crew performed their second fish assessment of the Eden Landing Ecological Reserve in early May.  They plan to perform two surveys per quarter over the next two years under contract with the Wetlands Regional Monitoring Program (WRMP).

Complications as the fish monitoring program expands into new areas. 

• The first monitoring event in April only covered seven stations.  Otter trawling can be a tricky business.  Even the best maps and thorough site visits can’t guarantee that channels will be deep enough and obstruction-free.  And, it has to be executed in conformance with rising and falling tides. … It was an ambitious first attempt.
• Generally speaking, the UC Davis plan is to have roughly ten stations at each new WRMP survey site.  So this time around, with more favorable tides, 13 stations were trawled.  This includes three offshore stations that were added at the downstream ends of each creek:  MEC-O, OAL-O, and WTS-O.  The “O” is for “Outside” or “Offshore.” 
• Name changes.  North Creek and North Creek Marsh stations are now labeled NCM1 thru NCM3.  (During trawls in April, the three stations were initially called “OAR.”  The name “NCM” is better.)

Thirteen trawling stations were sampled in May.  The expanded list of trawling stations is shown in north-to-south order.  Stations in each creek segment are listed from upstream to downstream. 

Reminder:  All WRMP-related sampling is performed using a 5-minute trawl duration.  This contrasts with Lower South Bay (LSB) trawls that have employed 10-minute trawls since 2014.  For simple “Catch Per Unit Effort” (CPUE) comparison of Eden Landing to LSB, multiply Eden Landing trawl results by two.

CPUE comparison Eden Landing versus LSB – some examples: 

• Baby Gobies.  264 Unidentified / Baby Gobies were caught at Eden Landing’s 13 stations.  (CPUE equivalent: 264 x 2 = 528!)  For comparison, April and May LSB trawls netted 308 and 714, respectively, from 20 stations.  This means two things:
  1) Eden Landing also experienced a “Baby Fish Month” in May, and
  2) Eden Landing is a significant baby goby nursery.
• 37 Chameleon Gobies.  (CPUE equivalent: 37 x 2 = 74.)  For comparison, relatively few Chameleons are ever seen in LSB.  Chameleon Gobies are well known to thrive at higher salinity.   Eden Landing is a saltier place.
• 0 Shimofuri Gobies and 0 Shokihazes at Eden Landing in May.  Both Shimo and Shoki Gobies are regular catches in LSB where salinity is lower and highly variable. 
• Halibut and Starry Flounder counts are encouraging.  Eden Landing totals in May were 6 Halibut and 2 Starries.  (Multiplied by 2 = 12 and 4.)  This compares to 18 Halibut and 8 Starries from the 20 LSB stations. These numbers are roughly comparable.  Halibut and Starries also recruit here.

The remainder of this report is organized geographically by creek or slough.  We are still learning this area.  Each waterway has its own characteristics.  Plus, we only have the first April trawling survey for comparison.  There is much to evaluate here but only two months of limited data.  We must crawl before we can run!

1. Mount Eden Creek (MEC).

Mount Eden Creek is the northernmost waterway in Eden Landing Ecological Reserve.  The critters tell us that this is a salty place.

• Chameleon Goby count = 9/37 (9 in Mount Eden Creek versus 37 in all of Eden Landing Ecological Reserve).  Chameleons were present in all creek segments at Eden Landing except for Whale’s Tail South.  Chameleons like higher salinity (above 20 to 22 ppt).  They look healthy and colorful here.
• Bay Pipefish count = 1.  The only Bay Pipefish was caught at MEC1
• Philine / Tortellini Snail count = 9/9.  All Philines were caught at MEC1.  Philines also like higher salinity.  (Philines are a mixed blessing.  They are non-native mollusk predators, but they are also documented killers of noxious Corbula Clams.) 
• Encrusting Bryozoan.  Encrusting Bryozoan is analogous to coral.  Tiny Bryozoan zooid animals are evolutionarily different from coral polyps, but collectively they form similar hard structures called “Bryoliths.”  (Wikipedia: https://en.wikipedia.org/wiki/Bryozoa)  Encrusting Bryozoan is yet another clue that salinity is consistently high at MEC1.  

Japanese Bubble Snail count = 14/1.  Sami gathered 14 bubble-shaped snails at MEC1 and one more at MEC2.  Dr’s Hobbs and Lewis subsequently determined from photos that these snails were very likely Japanese Bubble Snails.   

• Haminoea japonica  https://invasions.si.edu/nemesis/species_summary/567649 

“… a cephalasphidean sea-slug commonly known as the Japanese Bubble-shell snail.  It is native to the Northwest Pacific from northern Japan to Hong Kong. …

In 1999, it was seen in San Francisco Bay… It appears to be abundant in the south-central regions of the Bay from Oakland to Redwood City … It was found in Tomales Bay in 2008 (Hanson et al. 2012) and in San Diego Bay in 2013.” 

More evidence of high salinity at MEC2. 

• At the next downstream station, surface marsh is largely comprised of pickleweed and spartina. 
• Two Oregon Mud Crabs were caught here, two more at MEC3, plus three more at other stations.  (Notably, no Harris Mud Crabs were seen at any Eden Landing station in April or May.)
• Japanese Littleneck Clams, Atlantic Oyster Drills and Corbula Clams were present.

Decorator Crab count = 16.  All Decorator Crabs were caught at MEC stations.  These interesting crabs are only occasionally found in the deepest and saltiest parts of Lower South Bay (stations LSB1 & 2).  We call them “Decorators” because of their habit of decorating (camouflaging) their bodies with bits of living anemones, hydrozoans, and other sessile creatures.  Other people refer to them as “Pear Crabs” or varieties of Spider Crabs.

• These Crabs are a rare example of a California native invading other parts of the world.
• Tuberculate Pear Crab (Pyromaia tuberculata)  https://www.inaturalist.org/taxa/165487-Pyromaia-tuberculata 
  “P. tuberculata is considered an invasive species due to its spreading to the southeast Atlantic and western Pacific.^[4] After arriving in Japanese waters, P. tuberculata has thrived due to its ability to quickly recolonize waters following instances of summer hypoxia.^[11] Smaller, native crabs have limited breeding seasons which restrict their ability to compete with the invasive P. tuberculata.^[11] In eutrophic waters such as Tokyo Bay, P. tuberculata is abundant from the intertidal zone up to 80 meters of depth, with inner-bay populations being replenished each fall with larvae from crabs in the outer-bay, which do not experience the hypoxic die offs.^[5]”

Leopard Shark count = 1.  Only one adult shark was seen at the midpoint of Mount Eden Creek (MEC2).   The April count at Eden Landing was three sharks: one adult and two babies. 

Bat Ray count = 1/6.  A total of 6 Bat Rays were caught this month.  The Ray shown here at MEC-O plus: one at NCM1 (far upstream),  two at NCM2, and two more at OAL-O. 

• In April, the Bat Ray total was 9: one again far upstream at NCM1, another at NCM2, three in the OAL channel, three at MEC3, and one at WTS1. 
• These data suggest that Bat Ray mamas come into the various Eden Landing sloughs to give live birth to their litters of pups.  Each slough channel appears to support them. 

The MEC-O (outside or offshore station) characterizes fishes in the deep channel that leads from the Bay up into Mount Eden Creek. 

• Northern Anchovy count = 11.  All Anchovies in May were caught at MECO.  The net probably hit a small school swimming offshore here.  They were all young fish measuring between 40 to 70 mm.  No Anchovies were caught at Eden Landing the previous month.  
• Staghorn Sculpin count = 6/20.  (6 Staghorns were caught at MEC-O / 20 were caught at Eden Landing in total.)   

2. North Creek Marsh (NCM).

North Creek Marsh.  North Creek is a small tributary that drains restored areas of North Creek Marsh into Old Alameda Creek (OAL).  We use GPS for navigation, but landmarks are important to us.  A tall antenna on the levee marks the division between stations NCM1 and NCM2.

• Worm Tubes?  We saw these mud tubes at station NCM3 in April.  We presume some type of polychaete worm makes them.  Literature tells us that the fragile worms may escape, ball up, or disintegrate when the tubes are pulled apart.  Investigation continues.
• Anemone count = 33/65.  Just over half of anemones collected came from NCM stations.  Most of the rest were from OAL stations just downstream.  This must be a very anemone-friendly place! 

North Creek Marsh downstream: just above the confluence with Old Alameda Creek.

• Shiner Surfperch count = 1.  Last month, we caught 16 Shiners in this area during Shiner birthing season.  This month, only one. 

3. Old Alameda Creek (OAL).

Old Alameda Creek in modern times is mainly a stormwater conveyance for much of the City of Hayward and the East Bay hills.  The lower segments flow through dense stands of pickleweed.  (Significant landmark: a section of a giant log near station OAL1.)  https://acfloodcontrol.org/the-work-we-do/resources/old-alameda-creek-watershed/ 

• Corbula clam count = 63/83 at OAL1 + OAL2 + OAL3.  (Corbula photo not shown here.)  Corbula prefer flowing streams.  63 Corbula were caught at Old Alameda Creek (OAL) stations versus 20 everywhere else.    
• Musculista count = 264/289 at OAL1 + OAL2.  A big pocket of Musculista (Asian Date Mussels) resides near station OAL2.  In April, the Musculista count here (with fewer stations sampled) was 19 out of 21, or 90%.  Now in May, almost 90% of all Musculista were caught here again.  Musculista like station OAL2.

The far downstream end of Old Alameda Creek terminates in the Bay.  The water is increasingly salty and subject to tidal influence as we progress downstream.   
 

4. Whale’s Tail South (WTS).

Whale’s Tail South is at the far southern end of Eden Landing Ecological Reserve.  It drains a recently restored Whale’s Tail marsh area. https://www.usgs.gov/media/images/aerial-orthomosaic-photo-whales-tail-marsh-south-may-2022 

Station WTS-O lies offshore from Whale’s Tail South.  The waters on either side of the offshore channel support patches of Eel Grass.  Eel grass is very important.  We are careful to avoid trawling through Eel Grass beds here.   https://thewatershedproject.org/whats-in-your-watershed-eelgrass-in-the-bay/ 

• Eastern Mud Snail count = 172/193.  172 out of 193 Easter Mud Snails were collected at station WTSO-O alone!  Are these snails munching on the Eel Grass?  Or, are they cleaning disruptive algae off the Eel Grass?  More investigation is needed! 
• Gracilaria Red Algae.  We found a few sprigs of Gracilaria at far downstream stations in both April and May.  This type of red algae also shows up in LSB on occasion.

We expand our search into new parts of San Francisco Bay.  We record all we can on datasheets.  The rest we memorize in photos – or pass down amongst ourselves in spoken lore.

The Rolling Stones – Sing This All Together.   https://www.youtube.com/watch?v=2DjGjxvYLXU