scholarly journals Crime Scene San Francisco: Who Is Responsible for the Disappearance of Delta Smelt?

2021 ◽  
Vol 9 ◽  
Author(s):  
Mallory E. Bedwell ◽  
Craig Stuart ◽  
Melinda R. Baerwald
Keyword(s):  
San Francisco ◽  
Fish Species ◽  
Native Species ◽  
Crime Scene ◽  
San Francisco Estuary ◽  
Invasive Fish ◽  
Delta Smelt

Delta smelt are becoming harder and harder to find in the San Francisco Estuary. Some of the suspects in their disappearance are invasive fish species that were introduced from other places into the Estuary. These invasive fish can impact their new habitat by eating the native species that were originally there. However, it is hard to understand what the invasive fish are eating. We found that we can use the DNA in the stomachs of invasive fish to figure out what they have eaten. We caught a common invasive fish in the Estuary, called the Mississippi silverside, and analyzed the DNA from their stomachs to see if it matched delta smelt DNA. We discovered that some Mississippi silversides had delta smelt DNA in their stomachs! We therefore believe that Mississippi silversides are one of the culprits causing the disappearance of delta smelt.

scholarly journals Delivering Food to Hungry Fish in the San Francisco Estuary

2021 ◽  
Vol 9 ◽  
Author(s):  
Laura Twardochleb ◽  
Leela Dixit ◽  
Mallory Bedwell ◽  
Brittany Davis ◽  
Jared Frantzich
Keyword(s):  
Invasive Species ◽  
San Francisco ◽  
Fish Species ◽  
San Francisco Estuary ◽  
Fish Food ◽  
Yolo Bypass ◽  
Delta Smelt ◽  
Endangered Fish ◽  
The Past

The San Francisco Estuary is home to an important endangered fish called delta smelt. Delta smelt eat small, nutritious animals called zooplankton to survive and grow. In turn, zooplankton grow by eating microscopic plant-like organisms called phytoplankton. In the past, the Estuary was full of plankton and delta smelt. Because people have removed water from the Estuary and invasive species now live there, the Estuary no longer has enough plankton to feed delta smelt, making it difficult for them to survive. Scientists have found a unique place in the Estuary, the Yolo Bypass, that has lots of fish food. The problem is that delta smelt do not live in the Yolo Bypass year-round. Scientists are working to solve this problem by sending river or farm water through the Yolo Bypass, to move fish food downstream to feed the hungry delta smelt and other fish species.

Multidecadal trends for three declining fish species: habitat patterns and mechanisms in the San Francisco Estuary, California, USA

2007 ◽  
Vol 64 (4) ◽  
pp. 723-734 ◽  
Author(s):  
Frederick Feyrer ◽  
Matthew L Nobriga ◽  
Ted R Sommer
Keyword(s):  
Water Quality ◽  
San Francisco ◽  
Striped Bass ◽  
Fish Species ◽  
Habitat Suitability ◽  
Specific Conductance ◽  
San Francisco Estuary ◽  
Delta Smelt ◽  
Threadfin Shad

We examined a 36-year record of concurrent midwater trawl and water quality sampling conducted during fall to evaluate habitat trends for three declining fish species in the San Francisco Estuary, California, USA: delta smelt (Hypomesus transpacificus), striped bass (Morone saxatilis), and threadfin shad (Dorosoma petenense). Generalized additive modeling revealed that Secchi depth and specific conductance were important predictors of occurrence for delta smelt and striped bass, while specific conductance and water temperature were important for threadfin shad. Habitat suitability derived from model predictions exhibited significant long-term declines for each species; the southeastern and western regions of the estuary exhibited the most dramatic changes. Declines in habitat suitability were associated with anthropogenic modifications to the ecosystem. For delta smelt, an imperiled annual species endemic to the estuary, the combined effects of fall stock abundance and water quality predicted recruit abundance during recent years of chronically low food supply. Our results are consistent with existing evidence of a long-term decline in carrying capacity for delta smelt and striped bass and demonstrate the utility of long-term data sets for evaluating relationships between fish and their habitat.

scholarly journals Can Plants Be Engineers?

2021 ◽  
Vol 9 ◽  
Author(s):  
J. Louise Conrad
Keyword(s):  
San Francisco ◽  
Water Flow ◽  
Fish Species ◽  
Aquatic Ecosystems ◽  
Native Species ◽  
Ecosystem Engineer ◽  
Water Clarity ◽  
Ecosystem Engineers ◽  
San Francisco Estuary ◽  
Native Fish

When we think of engineers, we think of making a machine, like a car. Are there engineers for ecosystems? When an organism can make big changes to its environment, we call it an ecosystem engineer. In aquatic ecosystems like the San Francisco Estuary, underwater plants can be important ecosystem engineers because they can change water flow and water clarity. In the Estuary, a plant called Brazilian waterweed, which was introduced by humans, is one of the most important ecosystem engineers. With its leaves and stems, this plant traps tiny particles floating in the water, making the water clearer. Clearer water has made it easier for more plants to grow and these changes helped some non-native fish species to increase in number, while some native species declined. Introduction of Brazilian waterweed has led to an entirely different ecosystem, which has also affected how people use and take care of the Estuary.

scholarly journals The Spawning Migration of Delta Smelt in the Upper San Francisco Estuary

2011 ◽  
Vol 9 (2) ◽  
Author(s):  
Ted Sommer ◽  
◽  
Francine Mejia ◽  
Matthew Nobriga ◽  
Frederick Feyrer ◽  
...  
Keyword(s):  
San Francisco ◽  
San Francisco Estuary ◽  
Spawning Migration ◽  
Delta Smelt

scholarly journals The value of long-term monitoring of the San Francisco Estuary for Delta Smelt and Longfin Smelt

2021 ◽  
pp. 148-171
Author(s):  
Trishelle L. Tempel ◽  
Timothy D. Malinich ◽  
Jillian Burns ◽  
Arthur Barros ◽  
Christina E. Burdi ◽  
...  
Keyword(s):  
San Francisco ◽  
San Francisco Estuary ◽  
Delta Smelt ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
Longfin Smelt

scholarly journals Fish Misidentification and Potential Implications to Monitoring Within the San Francisco Estuary, California

2018 ◽  
Vol 9 (2) ◽  
pp. 467-485
Author(s):  
Joseph E. Kirsch ◽  
Julie L. Day ◽  
James T. Peterson ◽  
David K. Fullerton
Keyword(s):  
San Francisco ◽  
Fish Species ◽  
False Positive ◽  
Juvenile Fish ◽  
Monitoring Program ◽  
San Francisco Estuary ◽  
Full Time ◽  
Monitoring Programs ◽  
Observer Experience ◽  
Fish Monitoring

Abstract Fish monitoring programs often rely on the collection, species identification, and counting of individual fish over time to inform natural resource management decisions. Thus, the utility of the data used to inform these decisions can be negatively affected by species misidentification. Fish species misidentification bias can be minimized by confirming identification using genetic techniques, training observers, or adjusting monitoring data using estimates of incomplete detection and false-positive misidentification. Despite the existence of well-established fish identification training and quality control programs, there is considerable uncertainty about fish species false-positive misidentification rates and the effectiveness of fish identification training programs within the San Francisco Estuary. We evaluated the misidentification of fish species among Delta Juvenile Fish Monitoring Program observers by conducting five fish identification exams under controlled conditions at the Lodi Fish and Wildlife Office in Lodi, California, between 2012 and 2014. To assess the variability in false-positive misidentification, we fitted data to species and observer characteristics using hierarchical logistic regression. We found that fish species misidentification was fairly common, averaging 17% among 155 test specimens and 32 observers. False-positive misidentification varied considerably among species and was negatively related to fish size, the abundance of the species within monitoring samples, and observer experience. In addition, observers who were not formally trained or used as full-time observers were, on average, 6.0 times more likely to falsely identify a species. However, false-positive misidentification rates among observers and specimens still varied considerably after controlling for observer experience and training, and species and size, respectively. Our results could be used to improve fish identification training and testing, increase the accuracy of fish occupancy or abundance estimation, and justify the allocation of resources to continually use and formally train full-time observers within long-term monitoring programs operating in the system.

Sign in / Sign up

Export Citation Format

Share Document