An annual count of harbor seals off the coast stretching from San Mateo County to Sonoma County — seen as an indicator of the ocean’s health — showed no significant fluctuation, according to marine officials.
Conducted by the National Park Service with the assistance of volunteers, the survey is a manual count of adult and youth harbor seal populations. Because harbor seals are “top predators in the marine food web” and they respond to changes in oceanography and rising sea levels, they are looked to as a barometer of the condition of the marine ecosystem.
Survey results have supported marine officials’ efforts to create protected coastal areas to provide places for the animals to live and thrive, even when there are changes in their environment.
“These are protected areas in that people cannot go there,” said Sarah Allen, science adviser of Point Reyes National Sea Shore. “If there is a change in environment and climate, they can retreat to these protected areas on shore without disturbance.”
The number of times the harbor seals are counted increases between March 1 and July 31, when the seals are birthing and molting. Citizen scientists, Allen said, use binoculars and notepads to count the number of seals at low tide and average them throughout the week, every other week.
This year, between 3,200 and 3,400 seals were counted in the coastal areas between San Mateo County’s Fitzgerald Marine Reserve and Sea Ranch in Sonoma County, Allen said. Last year, there were roughly 3,800 adult harbor seals counted along the coast.
But the seal count at the Fitzgerald Marine Sanctuary in San Mateo County has dropped in recent years.
Four years ago, volunteers would count roughly 300 adult seals coming out of the water, according to Sarah Lenz, a park ranger with the San Mateo County Department of Parks.
Last year, roughly 191 adult harbor seals were found in the area. This year’s highest count was 250, she said.
“We haven’t seen a count of 300 in years,” Allen said.
There are a number of factors that could contribute to such a drop, she said.
“There could be a change in ocean conditions,” she said. “A coastal upwelling, which means there is less food, or people could be around.”
Harbor seals are described by the Marine Mammal Center, a Sausalito-based nonprofit, as having spotted coats. They can be shades of gray, silver or brown, and can grow to 6 feet in length and weigh up to 300 pounds. They are often found north of the equator and prefer to live in coastal waters near sandy beaches, bays and estuaries.
