Methods

01.

CDFW conducted open water surveys and shoreline surveys from Aug 29 to Sep 7, 2022.

02.

During surveys white and green sturgeon were identified and measured. Tissue samples and water samples were taken as needed.

03.

Data sets from San Francisco Estuary Institute (SFEI), iNaturalist, Cramer Fish Sciences, USGS and CDFW were aggregated.

04.

The data were manually analyzed to account for multiple reports of the same carcass, reports with more than one carcass, and potential misidentification.

05.

iNaturalist users were individually contacted when needed.

Timeline of Algal Bloom and CDFW Investigation

A timeline of the investigation into the SFE 2022 HAB event. The timeline reads as: First reports of bloom (Alameda) in Late July, bloom expanding to open-bay in early August, first observation of sturgeon carcasses on August 22, CDFW Open Water surveys begin on August 29, bloom begins to decline on August 29, iNaturalist projects created on August 30, Chl near pre-bloom and impact persists on September 1, CDFW shoreline surveys are conducted on September 6 and 7, CDFW receives datasets from late August to mid September, CDFW analyzes data from mid November to mid January, and CDFW prepares abstract on January 25.

How were sturgeon carcasses classified?

Sturgeon carcasses are more difficult to identify between species, considering the prominent features that make them easy to differentiate while alive and intact can be lost to scavenging and decomposition. However, confident identifications of some sturgeon carcasses were able to be affirmed.

Photo Credit: NOAA Fisheries. Green Sturgeon. https://www.fisheries.noaa.gov/species/green-sturgeon

Green Sturgeon

Olive-green to dark-green back with yellowish, green-white belly
Green stripe on each side and on belly
Pointed snout with barbels midway between the tip of the snout and mouth
Vent is located between the pelvic fins
8-11 sharp dorsal scutes

Photo Credit: NOAA Fisheries. Green Sturgeon. https://www.fisheries.noaa.gov/species/green-sturgeon

White Sturgeon

Grey back with solid white belly
No stripes on sides or belly
Blunted snout with barbels closer to the snout than mouth
Vent is located behind the pelvic fins
11-14 dull dorsal scutes

How did we get sturgeon carcass data from iNaturalist and how was the data "manually analyzed"?

A screenshot of an iNaturalist sighting. A photo of a sturgeon carcass sitting on rocks is on the top left, and an interactive satellite map with the GPS location of the report is on the top right. Below is a list titled "Annotations" where users confirmed different attributes such as the organism being alive or dead or the life stage. To the left is a column titled "Activity" where users suggest an ID for the report with explanations, agreements, and disagreements.

Figure 1: A typical sturgeon sp. carcass observation on iNaturalist. Hundreds of citizen scientists submitted observations similar to this one. Below the photo you can see how users suggested an ID before coming to a consensus. Under "Annotations" someone indicated the organism was dead.

A screenshot of the iNaturalist project "Aggregating SF Bay Harmful Algal Bloom 2022". There is an "About" section that describes the project as "collecting observations of dead organisms related to the 2022 Harmful Algal Bloom". The project's reports can be categorized as "Observations", "Species", "Identifiers", and "Observers". The "Species" tab is open and shows observations of striped bass, bat rays, white sturgeon, littleneck clams, mussels, pillbugs, and many different species of crabs.

Figure 2: Veteran iNaturalist users in the Bay Area created two projects, including the one above, to aggregate all of the observations related to the 2022 HAB event. In the photo you can see other species that were affected by the HABs event. As administrators of this project, our staff were able to filter for the sturgeon carcass data and download it.

The photo shows downloaded data from iNaturalist into an Excel sheet. This data is in the early stages of manual investigation. Observations are highlighted in different colors like red and green to denote further questioning, multiple sturgeon in one sighting, and other issues with the report.

Figure 3: Section of downloaded iNaturalist data from an excel sheet. The information in some of these extra columns was helpful during manual data analysis. It allowed us to determine with more confidence when an observation was a repeat, for example. Using different colors allowed us to note different situations, such as when an observation was a repeat, when we needed to ask an iNaturalist user a question, when there was more than one sturgeon in the observation etc.

A photo showing an Excel sheet of iNaturalist data that has been vetted. The data sheet contains categories such as date and time a report was made, the location site, GPS coordinates, names or usernames of the observer (blurred for privacy), source of the report, species ID, and further notes on the condition of the specimen.

Figure 4: A section of our "final data". After manually analyzing our data from different sources we combined into one data sheet, with only the essential information.