Fish in the Bay. – December 2025, Merry Fishmas 2025!
Merry Fishmas!
This is a small update from Longfin Smelt Broodstock trawls that the UC Davis crew has been conducting in Lower Coyote Creek over the last two weeks.
- Plus, a 2025 end-of-year update on some of our favorite fishes and bugs.
The crew is busy collecting adult spawn-ready Longfin Smelt for the “Broodstock” program. – This is the multi-year effort to culture a breeding population of Longfins at university facilities as a hedge against possible extinction of our SF Bay population.
1. Longfin Smelt Broodstock Trawls.
Dr. Hobbs & Sami Araya on the most recent 9th day of Longfin Broodstock trawls on December 18th.
We have been anxiously awaiting this current spawning season. 2025 was a grim year for Longfins in LSB. The Longfin spawn of 2024/25 started and ended early. Catch numbers were low. Over this entire calendar year, only 193 Longfins were counted; the lowest annual count since 2017. Monthly catches in November and December continued to be disappointing.
Sami & Alex Lama examining Longfins in Pond A21 & recording data.
However, the situation brightened a bit during Broodstock trawls. By mid-December OGFL researchers caught several hundred Longfins and retained more than half as eligible bachelors and bachelorettes for the program. Most of the captures were on the downstream side, closer to the Town of Alviso and restored Pond A21 on the west side of the railroad tracks.
Longfins on the downstream side are comprised mostly of females and juveniles. Females loiter downstream, mainly in restored ponds A19 and A21. They must consume enormous amounts of protein relative to their body size to support egg production. Basically, the Longfins are telling us that tiny food, like copepods and mysids, is present here.
- Each adult female feeds and waits for the right time to migrate upstream the last few miles to the spawning ground. Her belly swells with maturing eggs as she waits. We do not yet know what triggers her to make the upstream run.
- Other closely related smelt species, and less closely related Grunion, time their spawn based on the Spring Tides just after a New or Full Moon. We have not confirmed this kind of lunar timing in Longfin spawning, but we like to think it may be true.
On Thursday, December 18th, the crew moved upstream on Coyote Creek to station UCoy1. UCoy1 is the special site where large male Longfins have congregated to prepare their nesting places each of the last few years.
Once again, big male spawners were found. Jim Hobbs and Sami Araya caught roughly 40 big males. Most of these big boys were released because we presume they are more critically needed to sustain this year’s spawn. At least 12 big females were also caught at the UCOY1 spawning ground.
- As far as we know, this is a one-way trip for the males. Once they begin cleaning and guarding their upstream nesting place, they do not eat. This is an end-of-life mission for the boys.
- Sami’s examinations of Longfin gonads, on the other hand, strongly suggest that at least some females may live to spawn another day, perhaps even another season.
Longfins in Pond A21 on December 3rd just prior to the Full Moon & first wave of spawning.
The Longfin spawn of 2025-26 has begun! Sami determined that many female Longfins were already spawned out which tells us that the first wave of spawning probably happened after the first week of December. (Possibly just after the full moon of December 5th.)
Dr. Hobbs sees signs that the next wave of spawning is probably happening from now through Christmas and possibly as late as New Year’s Day.
- Big male Longfins are staged with spawning pads ready in upper Coyote Creek.
- The New Moon passed by on December 19th.
- Rain is forecast all next week. (Longfins love rainwater flushing.)
2. Other Winter Species are Arriving.
Staghorn Sculpin count = 15 for December / 1,050 for 2025. Staghorn numbers fluctuate wildly with ocean cycles. Their numbers jump up during, or just after, La Ninas. They get hammered by El Ninos. During the 2023/4 El Nino year, the Staghorn annual count dropped to just 194. They are still recovering.
- Big adult Staghorn Sculpin started arriving for their spawning season in November and December. Male Staghorns attract mates to underground burrows in the lower stretches of Coyote Creek and in restored ponds A19 and A21.
Starry Flounder at UCoy2 on 2 December.
Starry Flounder count = 4 for December / 69 for the year. The 2025 Starry count was just average. In bad years, we see only one or two Starries per month. In good years, like 2017, 2018, 2023, and 2024, we catch hundreds of them.
- Around this time of year, adult Starries swim upstream to spawn where creek and tide waters meet.
- Sami tells me that Starries are opportunistic spawners. When conditions are right, their numbers seem to explode for no apparent reason. Rainfall is a factor, but rainfall alone doesn’t explain the variable Starry recruitment we see.
American Shad count = 8 for December / 711 for 2025. This year started with “Shaduary.” We caught hundreds of American and Threadfin Shad in January and February. But then, as usual, Shad numbers dropped to near zero with the warm season. Overall, this was just an average Shad year.
The first few Pacific Herring and Pacific Tom Cods were also seen in December during Longfin Broodstock trawls. Unfortunately, no photos available.
Crangon shrimp at Alv3 on December 3rd. (Small Palaemon shrimp on the left.)
Crangon Shrimp count: 1,856 for December / 32,823 for 2025. We are just entering Crangon brooding season. Adults started showing growing egg masses in December. They will begin brooding eggs by January. The 2025 Crangon count was just average for years since 2017. (2015 through 2017 were horrible years for Crangon.)
3. Some Summertime Species are still sticking around.
Young Halibut at LSB1 on 3 December.
California Halibut count = 22 for December / 245 for the year. Halibut love El Ninos. The numbers increased in 2024 and this year. However, the strong El Nino years of 2015 and 2016, still stand as our record Halibut years by far.
Baby Halibut at top. Young Anchovies at bottom. LSB2 on 3 December.
Anchovy count = 44 in December / 2,600 for 2025. This was the worst year for Anchovies since 2019 and the fourth-worst year since 2012. We don’t know what went wrong here. There is no clear ENSO connection. 2025 was just a bad Anchovy year. Go figure!
- As usual, the numbers peaked during the summer months, June through September, as adults arrived to spawn. Now we are seeing a bit of a lull as babies and young-of-year juveniles start to show up.
Bat Ray count = 2 in December / 200 for the year. 2025 is our second-best Bat Ray year ever. Only 2023 was better with 206. Bat Ray numbers in LSB have been climbing fairly steadily since 2012 at least. In any year before 2021, even fewer than 100 Rays would have been an annual record.
4. Christmas Duck!
Christmas Duck! Sami spotted this red, white and green Northern Shoveler paddling along the bank near UCoy2. Local hunters nickname these ducks “spoonbills” or “spoonies.” Flocks of them begin arriving in LSB around September. Brightly colored males pair off with brown-drab females as they fuel up over the winter for their big migration back north in the spring.
Merry Fishmas and a Happy Longfin New Year!
Michael Buble – Have Yourself A Merry Little Christmas [Official HD]
https://www.youtube.com/watch?v=l3l83C-we-k
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