The gray whale migration continues to be fraught with dangers, and researchers now believe two whales found days apart likely were mother and daughter that died after being struck by ships.
The whales that stranded on beaches in the San Francisco Bay Area died from blunt force trauma that can be attributed to ship strikes, scientists said Friday.
Necropsies — autopsies of animals — showed cause of death for both whales as blunt force trauma. The mother whale had deep propeller wounds that severed her fluke. Both mother and daughter were otherwise in good condition, meaning they weren’t suffering from malnutrition.
Seven whales have been found dead in San Francisco Bay waters since mid-March — three from malnutrition, three from being struck by ships and one still unknown.
The gray whale that surfaced in Pacifica, Calif. was the second gray whale this month that scientists confirmed died due to ship strike. (Photo Credit: Katie D’Innocenzo / The Marine Mammal Center)
A third necropsy completed on Thursday on a carcass found in Richmond, Calif., indicated yet another gray whale, also a 30-foot sub-adult female, may have died due to ship strike. The research team discovered deep propeller wounds that had severed its fluke, and it was in otherwise excellent body condition, indicating it was not malnourished.
Scientists suspect that the whale found in Richmond was the mother of the calf that died due to ship strike two weeks ago — the two were seen foraging near San Mateo days before the calf’s carcass surfaced. According to the Center, genetic testing will be conducted to confirm the theory.
“We’re incredibly concerned to discover the death of three gray whales due to ship strikes in two weeks,” Dr. Padraig Duignan, Chief Research Pathologist at The Marine Mammal Center, said in a statement. “Investigating each death is critical so that decision-makers can advise on shipping speeds in areas where whales are known to travel.”
The gray whale that surfaced in Pacifica, Calif. was the second gray whale this month that scientists confirmed died due to ship strike. (Photo Credit: Katie D’Innocenzo / The Marine Mammal Center)
Blunt-force trauma from ship strikes, malnutrition and entanglements are the most common causes of death in whales The Marine Mammal Center’s research team has investigated. Since March 10, seven gray whales have been found dead in San Francisco Bay waters.
“The death of seven gray whales in the San Francisco Bay Area this year is a cause for serious concern as it speaks to the broader challenges this species continues to face,” said Duignan. “The findings of these investigations are incredibly valuable as they can help policymakers find long-term environmental solutions to help prevent these incidents in the future.”
“We’re incredibly concerned to discover the death of three gray whales due to ship strikes in two weeks,” Dr. Padraig Duignan, Chief Research Pathologist at The Marine Mammal Center, said in a statement. “Investigating each death is critical so that decision-makers can advise on shipping speeds in areas where whales are known to travel.”
Scientists discovered deep propeller wounds on a gray whale carcass in Richmond, Calif. that had severed its fluke. (Photo Credit: Barbie Halaska / The Marine Mammal Center)
Blunt-force trauma from ship strikes, malnutrition and entanglements are the most common causes of death in whales The Marine Mammal Center’s research team has investigated. Since March 10, seven gray whales have been found dead in San Francisco Bay waters.
Biologists have observed gray whales in poor body condition during their annual migration this year potentially due to anomalous oceanographic conditions over the past few years that have contributed to shifting food sources. Malnutrition was the cause of death for three other gray whales that have stranded since March. A seventh whale carcass surfaced in Hercules, CA, and an investigation is pending.
“Many of the gray whales traveling through the relative safety of our outer coast waters of the sanctuary are detouring into the dire straits of San Francisco Bay in an act of desperation,” said MaryJane Schramm, spokesperson for the National Oceanic and Atmospheric Administration’s Greater Farallones National Marine Sanctuary. “Anyone on boats and other watercraft should prevent additional stress by staying at least 300 feet away and give them every break you possibly can.”
Gray whales are one of the most frequently sighted whales in California. The cetaceans can be seen passing by California in December and January during their southern migration, and again in April and May on their northern journey.
The eastern North Pacific population of gray whales has returned from the brink of extinction thanks to protections that prevented hunting. However, all species of whales still face threats such as ship strikes, entanglements, and shifting food availability.