Marine biology professor Lisa Needles and a team of researchers are conducting research on the repopulation of sea otters in California. They have found some of the best habitats in estuaries throughout California.
The California sea otter population — or Southern sea otters — were nearly hunted to extinction in the 1800s, but they were recovered from a small remaining population in Big Sur.
“In 1911, a small group of about 50 otters were found off of Big Sur because that area was inaccessible,” Needles said. “Those 50 individuals are what all of our otters in California are descended from.”
Thanks to conservation efforts, the population has rebounded to around 3,000, but it still remains at a historical low.
Sea otters, which are now classified as an endangered species, have been associated by both the general public and by scientists with kelp forest communities. Needles’ research team has found that estuaries, like the San Francisco Bay or Drakes Estero, could also be good environments for sea otters to expand their numbers.
An estuary is the tidal mouth of a large river, where the tide meets the stream. Estuaries also provide ample amounts of food and are shallow, so the otters don’t have to dive deep for their prey, according to Needles. Needles added that estuaries have been overlooked as beneficial environments for otters, and they were once a habitat that otters used frequently.
“Estuaries provide protection from great white sharks, which is the biggest thing that is keeping otters from expanding their range, moving north or south,” Needles said. “Estuaries also allow places for otters to ‘haul out’ which means they come onto land so they can conserve energy.”
By comparing the environment in San Francisco Bay to that of Elkhorn Slough in Monterey, the team was able to make an estimate of how many otters San Francisco Bay could support. They determined that it alone can support about 6,600 sea otters, more than double the 2018 California population.
Unfortunately, simply moving the otters to San Francisco Bay is not a realistic option, Needles said.
“There’s a big difference between the otters being transported to San Francisco Bay by humans and that naturally occurring,” Needles said. “Otters also eat foods that we are interested in, like sea urchins and crabs. People like to hunt these, so there is some conflict there.”
The team’s research has consisted of food availability of these different habitats as well as the eating habits of the otters. They team was able to identify what the otters were eating, how much they ate and how long they spent eating their prey, or what they call the “handling time.”
“Our research on eating habits gives us an idea of how much food is out there for them because different prey items have different calories, providing differing amounts of energy,” Needles said.
Sea otters are a keystone species. This means that their role in the environment has a greater effect than other species. Otters eat sea urchins that are eating the kelp forests. If the otters are removed from the environment, the sea urchins destroy the kelp forest. The team found that the same thing was happening in Morro Bay with crabs and eelgrass.
“We are looking at how otters affect the eelgrass population in Morro Bay,” Needles said. “When otters are present, they control the crab populations.”
Needles said she was inspired to start sea otter research in 2002, while completing her Master’s degree at Cal Poly. During the process of researching invasive species in Morro Bay, she said she noticed a decline in the muscle population and a rise in the non-native species, Bryozoan. Otters are known to prey on muscles, so she began to research association between them, peaking her interest in sea otter repopulation research, she said.
Shyenne Heuer, one of Needles’ undergraduate student researchers, says that understanding sea otter prey and limitations for feeding is integral for population regulation and recovery.
“Once we get a better grasp of the sea otters’ diet, we can start to get into the ways of how we are interrupting that delicate process,” Heuer said. “In order to protect a population, we need to know what resources they depend on, and only then can we attempt to properly regulate and limit human interference between us and the sea otters.”
Biological sciences senior Lucy Passaglia said she finds this research to be very beneficial to sea otter repopulation and to the ecosystem as a whole.
“Every species is important in an ecosystem,” Passaglia said. “If a certain species is going extinct, it’s our job to try to maintain their population, especially if their extinction is a direct result of human interference.”