In 2019, more than 30 adult striped bass were found in Narrow River without a clear sign of what had killed them. NRPA worked with National Oceanic and Atmospheric Administration (NOAA), Rhode Island Division of Fish and Wildlife Outdoor Education and Kennebec River Biosciences, a lab in Maine, to try to determine what had caused this mortality event. Read about this mortality event below.
CLICK HERE to see a spreadsheet noting as much detail as we have about this year’s die-off. We will update the spreadsheet as data comes in. Photos of dead striped bass from this year is below.
This year, we have started receiving reports of dead adult striped bass that seem similar to last year’s event. We have alerted our team of scientists so we can do more research into the cause.
HOW YOU CAN HELP:
If you see a dead striped bass floating somewhere in Narrow River, PLEASE email us and tell us:
- the date and time
- location
- estimated length
- whether or not the eyes are still intact (ONLY IF it is safe for you to go close enough to see)
We are seeking a fish who has very recently died (eyes still intact and body in good condition) to send to the lab for testing.
We DO NOT recommend you pick up the dead fish!
Thank you in advance for your help.
Dead striper found 9/1/20 at Edgewater boat launch. This specimen was sent to Kennebec River Biosciences in Maine for analysis. 
Deceased bluefish seen at the boat ramp at the end of Pettaquamscutt Terrace August 30, 2020. This was the first confirmation of the death of adult fish of a species other than striped bass. 
Dead fish found September 1, 2020 at Edgewater neighborhood beach. 
Dead striped bass seen off of Edgewater community on east side of river in Lower Pond on August 1, 2020. 
Dead striped bass found 400m north of URI boat dock on the west side on July 18, 2020. 
Dead striped bass found north of Gooseberry Island August 1, 2020. WE DO NOT recommend picking up the dead fish.
Striped Bass Mortality Event in Narrow (Pettaquamscutt) River August 2019
November 19, 2019
Authors Catalina Martinez, NRPA Board Member; Sharon MacLean, Research Biologist, NOAA Northeast Fisheries Science Center (Ret), Narragansett Lab
In early August 2019, there was a striped bass mortality event that lasted for several weeks from the mouth of the Narrow River to Gilbert Stuart Brook. Wind and current patterns in the river made it impossible to determine exactly where in the river fish may have died.
Routine dissolved oxygen measurements by NRPA’s River Watch program, and situational testing by the Rhode Island Department of Environmental Management (RI DEM) based on dead fish sightings, confirmed oxygen levels were within normal range during the time of the mortalities. As seen from the history of anoxic water turnover events in the upper Narrow River, low oxygen events impact multiple finfish species. For these reasons, low oxygen was ruled out as a possible cause. Water temperatures in the lower and upper ponds reached 87-89 degrees F as measured by a boat temperature probe around the time of the mortality event. This is higher than normal and is the upper range of lethal temperature tolerance for striped bass.
The first report of dead fish in the river was made on August 2 and sightings continued for several weeks. On August 10, 32 dead fish between 12 and 28 inches in length were counted in various stages of decomposition. Fin rot and external tissue hemorrhaging were common among fish inspected which are suggestive of pathogen involvement.
Two fish that appeared recently deceased were collected within a few days of each other and sent to Kennebec River Biosciences in Maine for bacterial and viral screenings (see photo). The bacterial screening of one fish specimen showed heavy pure growth of a subspecies of Photobacterium damselae that is associated with disease and mortalities in many finfish species. All viral screenings were negative. The second fish was too decomposed for study.
Although positive results from one fish alone do not provide enough evidence to conclude that all mortalities were due to this pathogen, P. damselae is known to cause severe finfish mortalities under the right conditions. A significant environmental stressor, such as higher than normal water temperatures, can increase susceptibility of fish to bacterial pathogens. Since high temperature also increases bacterial growth rates, it is possible that this pathogen combined with high water temperatures contributed to the August mortality event in Narrow River.
Photobacterium damselae is a widespread pathogen in the marine environment. Although there are no known human health risks to eating the fish or from swimming in the river with the pathogen present, it is recommended that people with immunodeficiency and/or open wounds be careful when handling fish that look diseased. Leaving diseased fish in the water to decompose can enhance the pathogen load in the river, so it is prudent to dispose of dead fish in the trash.
As water temperatures continue to increase as an inevitable impact of global climate change, we may see more finfish die-offs in the future. Thankfully, NRPA now has collaborators in place who are eager to work with us in the event of future issues.
Thanks to the following individuals, agencies, and organizations who assisted this effort on very short notice. NOAA NEFSC, RIDEM, RI Fish and Wildlife, NRPA Board Members, Marta Gomez-Chiarri, Professor and Department Chair, URI Department of Fisheries, Animal, and Veterinary Science, Cem Giray, Chief Science Officer from Kennebec River Biosciences in Maine, Jim Roche, James McGregor, and Narrow River residents.
