Day

September 13, 2020
13
Sep

Yet another non-native aquatic species may have made itself at home in the Delta.

As described by US Fish and Wildlife Service fish biologist Brian Mahardja and his co-authors in San Francisco Estuary & Watershed Science, the newcomer is an inch-long, minnow-like fish called the bluefin killifish (Lucania goodei), indigenous to Florida and adjacent southeastern states. It was first detected in the Delta Cross Channel during a beach seine survey in October 2017, and subsequently found in Beaver and Hog sloughs and at Decker, Sherman, and Brannan islands. With surveys curtailed by the coronavirus pandemic, current data is sparse, although 13 were caught before March and one was caught in June. Bluefin killifish are popular in the freshwater aquarium trade, and the authors suspect the founders of the Delta population were released by a...
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13
Sep

By looking solely at the results of a single annual fish-counting survey, Californians may be seeing an incomplete reflection of Bay-Delta fish population trends.

A team of scientists analyzed 14 survey programs carried out by state and federal agencies, as well as UC Davis, and concluded that employing such a diverse variety of long-term surveys is essential for accurately tracking and assessing the overall health of San Francisco Estuary’s ecosystem and its resident fishes. The research is described in the June issue of San Francisco Estuary and Watershed Science. Lead author Dylan Stompe, of UC Davis, explains that the research arose from concerns that too many people – reporters included – have relied on the results of one annual survey, the California Department of Fish and Wildlife’s Fall Midwater Trawl, to make sweeping conclusions about the health and abundance of several fish species. The...
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13
Sep

A unique adaptive behavioral trait that may once have helped winter-run Chinook salmon thrive in the Sacramento River system could now be working against the fish as they face extinction.

The trait – which cues fish when to spawn based on water temperature – isn’t syncing up with current conditions in the Sacramento River below Shasta Dam. A paper published in the June issue of San Francisco Estuary and Watershed Science, reports that cooler springtime river temperatures seem to prompt earlier winter-run spawning while warmer temperatures push back the peak spawning period by a week or two. Under historic conditions, when winter-run Chinook spawned in high-elevation streams now inaccessible to the fish, their behavioral adaptability would have helped the temperature-sensitive eggs and offspring in two ways—by ensuring “sufficient time for egg maturation in cool years, while secondarily preventing egg and alevin mortality in warm years,” write authors Eva Dusek Jennings,...
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wetland landscape photo
13
Sep

Better scientific preparation could help Delta water and environmental managers respond to droughts more effectively.

That’s one key takeaway from a review of environmental management and the use of science during the 2012-2016 drought commissioned by the Delta Science Program and published in the June 2020 issue of San Francisco Estuary and Watershed Science. “There are lots of mysteries about how to manage water to benefit species, agriculture, upstream and downstream users. I think science is going to be the best solution,” says lead author John Durand of UC Davis’ Center for Watershed Science. Durand and his team based their review on available reports and data, as well as discussions with agency staff, stakeholders and researchers. They focused on water management actions during the drought through the lens of four priorities identified by water managers:...
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