More sharks and more people enjoying activities in and near the water might explain why a greater number of sharks have been spotted recently, according to researchers and local water authorities.

In fact, for the first time, authorities posted signs at local beaches warning the public of shark sightings. The signs also could have helped make people more aware of how to report such incidents.

Whatever is responsible for the increase in local shark sightings, experts say Central Coast residents should not be alarmed by the changes.

Shark advisories went up five times between July and September, with signs posted at 17 predetermined locations and lifeguard towers along Santa Barbara beaches.

Three of those advisories, which are all posted for 72 hours after a reported sighting, went up in a two-week span between Aug. 14 and Aug. 27.

Mick Kronman, harbor operations manager with the city’s Waterfront Department, said he’s been working with the Parks and Recreation Department to post signs this year because of the increase in shark sightings and shark attacks on marine mammals.

“It’s very unusual to see this many white sharks in our area,” Kronman said last week. “They’ve been really close.”

Local marine researchers say they’re hopeful that the increase in sightings means that great white shark populations are making a comeback from severe overfishing, which occurred before the Marine Mammal Protection Act was passed in 1972.

A growing number of people surfing, diving and fishing are also affecting the trend, said Jennifer Caselle, research biologist at UC Santa Barbara’s Marine Science Institute.

“More and more people are enjoying the water now,” Caselle said. “More people are surfing. More people are getting into stand-up paddling now. Now anyone can report it.”

As a surfer and diver herself, Caselle said she isn’t worried about coming across a shark.

“We really need sharks in our oceans,” she added. “Restoring sharks brings you one step closer to restoring ecosystems. It does appear that the protections are working, and I think that’s a good thing.”

An increase in great white shark sightings along the Santa Barbara coastline is not unusual when considering the predators’ migration patterns, said Santa Barbara City College marine biology instructor Michelle Paddack.

The sharks seem to be feeding now before their winter migration toward Hawaii for breeding, Paddack said.

“It is absolutely in line with what we know about their feeding patterns,” she said.

Researchers know less about great white sharks than other types because they’re harder to find and to keep in captivity.

The negative stigma associated with the toothy predators is another factor, Paddack said.

“There has been a negative perception of sharks in our society in general,” she said. “The movie Jaws definitely started a negative perception. They are a potential predator of us, so anything that can hurt us we tend to want to avoid.”

In addition to an increase in shark sightings, Kronman noted a greater number of shark attacks on marine mammals — seals in particular.

Kronman said 10 seal carcasses with shark bites and injuries washed ashore over the summer.

That brings the total number of shark incidents to 20 since April.

“We’re just trying to inform the public,” Kronman said. “We’re not trying to alarm anybody.

“We are hopeful that this is either a seasonal phenomenon or a unique ecological phenomenon this year, and that we see fewer sharks in the future.”

Noozhawk staff writer Gina Potthoff can be reached at Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.