Fish in the Bay – 6 August 2017 UC Davis trawl – A good year for Starry Flounder

August 6, 2017 Jim Ervin

Fieldwork, Fish in Lower South Bay, News

A short August update. I rode with the UC Davis crew on 6 August on the Artesian/Upper Coyote Creek side.

Unfortunately, an ongoing family emergency kept me from participating on the Saturday Alviso run, so I missed seeing the charismatic elasmobranchs. You can see in the data tables below, the Hobbs trawls caught 9 Bat Rays and 2 Leopard Sharks, mainly far out in Lower South Bay where they tend to be most common. Last month the count was 5 Leopard Sharks and one Ray. This continues to be good confirmation that sharks and rays are recovering from the February Freshwater Flush of 2017.

Saturday – Bay side:

Sunday – Upstream side:

Dissolved Oxygen (DO) was not quite as low as the previous month (8-9 July), especially at upstream/Coyote Creek stations. You may recall that DO was below 4 mg/l at eight of 10 upstream stations last month – even well below 3 mg/l at four of those stations! Nonetheless, fish abundance and diversity remained pretty much the same.

Yellowfin Goby Grand Slam. We found Yellowfin Gobies at all stations for at least the second month in a row. The spring freshwater flush helped recruitment of a lot of creatures, like Longfin Smelt, Prickly Sculpins, Starry Flounder and such. Unfortunately, it also helped the noxious invasive Yellowfin Gobies.

Above: Pat Crain directs Jim Hobbs as he connects truck to boat. The typical Sunday trawling day starts early at the San Jose-Santa Clara Regional Wastewater Facility (RWF). The RWF gives UC Davis fish researchers great fenced, lighted, and patrolled security for their boat and equipment. Some may wonder; why have fences at a wastewater plant? … I can tell you from experience, we encounter trespassing people or signs of trespass at least a few times per year. Believe it or not, people occasionally try to break in.

Pond A16 – Not so green. Last month, water discharging from Pond A16 was conspicuously green as was much of Artesian Slough and even parts of Coyote Creek. The waters browned up quite a bit since then. Below I show a July versus August side-by-side comparison; roughly same time of day and same stage of tide. The phytoplankton-driven color change varies by season: temperature, salinity, photic period, and such. We have noticed for some years that Pond A18 water shifts from green to brown over the summer. It would be fun to describe the cause and develop an index …. some day.

Pond A18 = Green Water. In contrast, discharge from Pond A18 continued to be noticeably green on August 6^th. Pond A18 is currently drawing freshwater in from Artesian Slough, unlike A16 which draws saltier water from Pond A17 and Lower Coyote Creek. But, which is better for the local environment? Green water or brown water? Or, does it make a difference? We seem to have a lot of fish either way!

Striped Bass. Speaking of fish, these were four of the 12 Striped Bass caught at the first station in Artesian Slough.

Here come the Yellowfins. Further downstream we began to see greater numbers of Yellowfin Gobies, invertebrates (showing Synidotea here) and some juvenile Starry Flounder.

Palaemon shrimp. More shrimp were caught on the upstream side in August, fewer in the deeper Bay. I can’t say if the difference between July and August was random or seasonal variability. The UC Davis crew still caught a lot of shrimp: 2536 on Saturday, 785 on Sunday. Some of the Palaemon shrimp, shown below, had an interesting reddish hue.

Clearer-bodied Exopalaemons were more numerous in “Dump Slough,” AKA the Coyote Creek by-pass channel.

Mysids also continue to be present. (Here showing mysids next to a small, unusually clear-bodied, Palaemon shrimp.) Though not true shrimp, for all intents, mysids are midget shrimp. As mentioned before, Mysids are the primary diet of California Gray Whales, and pretty much anything bigger than a mysid.

Northern Anchovy numbers are increasing as summer continues. Local newspapers and magazines report that Humpback Whales are congregating off the Golden Gate now because of abundant Anchovies swarming to the Bay. https://baynature.org/article/ask-naturalist-humpback-whales-san-francisco-bay-right-now/ Now you know some of those Anchovies are heading to Lower South Bay and especially Ponds A19 and A21.

Starry Flounder. The other notable discovery this month was really good recruitment of Starry Flounder. We think this is part of the ongoing after-effects of the February Freshwater Flush. Starry young seek freshwater. These are a couple of photos I also posted on my Facebook page: Emily Trites showing us the baby flounder tray.

Close-up of the tray: If you look closely, you can see that we caught both right-eyed and left-eyed flounder.

Atriplex prostrata (Fat Hen) Last month, I noted a new plant (new to me) colonizing the mud flat in Pond A19. Christina Toms contacted collaborators to confirm that the plant is Atriplex prostrata, otherwise known as “Fat Hen.” It is a very common, non-native, salt marsh plant in this area.

More Fat Hen. A patch of it in Pond A19 at high tide next to some pickleweed.

Pond A19 summer vegetation. We can peek inside Pond A19 as we pass at mid-tide. The mud flat greens up quite nicely. Some of the dark green massy material is Ulva, or sea lettuce. The tall plants are cordgrass. This photo caught a harbor seal in the foreground.

This is a wider shot showing the summertime mudflat – very slowly evolving into marsh. The Freshwater Flush last winter beat this vegetation down to nearly bare mudflat. Salt marsh spartina springs back very rapidly.

Corbula. If you follow my Facebook page you have seen that I officially declared war on the Corbula clam. We don’t see a lot of them in Lower South Bay, which is a very good thing. I will do all I can – one tiny clam at a time.

BONUS Photos: Aerial Combat!

A White-tailed Kite hovering over a stand of lepidium alongside Dump Slough was clearly out of bounds. A Northern Harrier (AKA: Marsh Hawk) soon swooped in to harass the intruder.