Along the shore of Monterey Bay there’s a place where shorebirds flock by the thousands and sea otters and harbor seals find refuge in quiet waters. This is Elkhorn Slough, a seven-mile channel flanked by salt marsh and oak-covered hills. At first glance, it doesn’t seem like a particularly promising place for endangered wildlife, as California’s largest power plant, a busy highway, and a bustling harbor are all situated near its entrance. But those who venture into the slough (rhymes with “blue”) will find one of the most productive ecosystems on the planet, featuring a wetland that hosts more than 250 species of birds, 500 invertebrates, and hundreds of other animals, including seven endangered or threatened species. Some locals call this the cosmic center of the universe, and after a day’s visit, it’s not hard to see why.
From above, Elkhorn Slough looks like an elk’s antler, and the name reminds us of a lost era when large herds of tule elk populated the area. Just 200 years ago this area was inhabited by the Ohlone people, who shared the land and its surrounding waters for thousands of years with elk, grizzlies, otters, seals, and waterfowl. They hunted sea otter, deer, elk, and birds, but mainly ate shellfish, a fact confirmed by excavation of shellmounds—fossil trash piles—found around the slough. Despite the changes wrought on the landscape since that time by European settlers and their descendants, the slough is one of the most intact wetlands left in California.
The best way to explore this waterway is in a kayak, though hiking trails on the eastern side of the slough are also a good option. Fortunately, Moss Landing’s North Harbor at the mouth of the slough (on the west side of Highway 1) has two kayak outfitters who can set you up with everything you need. (Be sure to check tides, currents, and wind conditions before setting out, as these can turn a normally easy paddle into a tiring struggle against the elements at day’s end.)
As you paddle east beneath the Highway 1 bridge, the realm of wildlife immediately envelops you. Pelicans soar silently above, otters and seals dot the channel ahead, and the water below teems with life.
- An adult male southern sea otter wraps himself in eel grass tokeep from drifting while he rests in Elkhorn Slough. Photo by SuziEszterhas.
Bucking the current coming out of the slough, you could easily imagine Elkhorn as a river snaking its way through the rolling hills and emptying into Monterey Bay. But this channel is actually a tidal “arm” of the bay pointing east, bending at the elbow and continuing north with fingerlets branching out into an array of tiny creeks. About one million years ago, there was indeed an ancient river that gouged out this valley. But years of movement along the San Andreas Fault caused the river to change its course, leaving the valley high and dry. As sea levels rose following the last ice age, beginning about 12,000 years ago, the valley slowly filled with water and became the slough we know today.
Throughout the slough’s history it has remained a place of change and adaptation. It is primarily a salty embayment, but from time to time over the past 12,000 years the Pajaro and Salinas Rivers have flowed through Elkhorn on their way to Monterey Bay, creating an estuarine environment. In 1908, local farmers rerouted the Salinas to create more agricultural land, thereby permanently separating the river from the slough. Today, the ebb and flow of the tides wash its muddy banks twice a day and replenish the nutrients lost to the drying sun. This is a textbook definition of a slough—a slow moving body of water with muddy banks. This one happens to be saltwater, but sloughs can be freshwater as well. Elkhorn is now considered a seasonal estuary, as water runoff from winter rains turns the north end of the slough brackish.
As you paddle east up the main channel, you will pass the Moss Landing Wildlife Area, managed by the California Department of Fish and Game (DFG), on your left. Accessible only from land, this area has a short trail that leads to an overlook, but beyond that lies an expanse of shallow saltwater ponds that make perfect nesting habitat for shorebirds. The snowy plover, a threatened species, has been nesting here for the past few summers. Keen observers might catch a rare view of these tiny birds, distinguished by their black neck patches and hunched-over stance.
A short distance ahead, the main channel spreads out and curves south before continuing east. This prolific area is known as Seal Bend for the many harbor seals that rest on its muddy banks, often in the company of dozens of brown pelicans. Unlike their sea lion cousins, harbor seals have rear flippers that are fixed behind them, making it awkward for them to move on land and impossible to sit up. But in the water these rather fat marine mammals maneuver with graceful ease.
- Large numbers of harbor seals haul out to rest on the muddy banks of Seal Bend in Elkhorn Slough. Photo by .
Little is known about the social behavior of harbor seals, as they spend most of their time in the water, even to breed. They come ashore mainly in the spring and summer to give birth and molt (shed their fur). It is thought that marine mammals haul out in large groups like this for protection from predators. Out in the nearby open waters of the bay, where the harbor seals go to feed, they are prey to great white sharks and other large predators. But here at Seal Bend, they have found a predator-free expanse of muddy shoreline to loaf and pup, in close proximity to a plentiful food supply.
Seal Bend is also a good place to see the slough’s resident southern sea otters, who come here to feed heartily on the abundant clams, crabs, and innkeeper worms (tunnel burrowers about seven inches long that look like slippery hot dogs). Just before the bend, a sheltered cove with a small patch of eelgrass provides important habitat for the otters. They congregate here in small groups or “rafts” and wrap themselves in the eelgrass, just as they wrap themselves in kelp out in the bay, so as not to drift away while resting.
Until recently, you could commonly find up to 50 otters resting or grooming here, more otters than you could have found along the whole coast of California back in the early 1900s. Nearly wiped out by fur hunters by the end of the 19th century, California’s sea otter population rebounded to a peak of 2,377 in 1995, thanks to the Marine Mammal Protection Act and other restrictions on boating and fishing. But then the population declined by almost 10 percent to 2,139 in 2002. And in the first four months of 2003, 100 otters turned up dead on local beaches. A new study by researchers from UC Davis has identified several causes for these deaths, including a parasite found in cat feces that impairs otters’ brain function, leaving them more susceptible to shark attacks, boat collisions, and starvation. Necropsies of dead otters also found a surprising number of diseased hearts; the cause of these heart failures is unknown. The recent spate of mortalities is a major concern, especially as almost half the dead otters have been of prime breeding age, between four and nine years old.
Given the precarious state of the otter population, it is incumbent on boaters not to disturb the remaining animals. Current regulations require that you stay at least 100 feet from otters and other marine mammals. That can be a challenge here, as otters and harbor seals may pop up right next to your boat. In that case, remain quiet and resist the temptation to approach or touch the animals. And give a wide berth to haul-out sites.
Lying unseen underwater at the mouth of the slough is Monterey Canyon, the hidden source of the slough’s abundance of life. Stretching nearly 60 miles out to sea and plunging two miles deep, this chasm is deeper than the Grand Canyon. Each spring, cold, nutrient-rich water from deep within the canyon rises to the surface and flows into the slough with the tides. This causes a bloom of algae, or Enteromorpha, seen as bright green mats that eventually bleach white as they decay. As these plants die, the resulting detritus feeds the single-celled animals (diatoms and other plankton) of the slough, turning the waters into a rich soup that nourishes the clams and worms. They, in turn, will become food for the fish, birds, and other animals.
- Brown Pelicans feed by diving headfirst into the water to grab their fish prey. Photo by .
Brown pelicans are another endangered species that has taken advantage of the slough’s riches. Each summer they arrive by the hundreds from their southern breeding grounds to feed on the bounty of top-smelt and anchovy, small schooling fish that crowd into the slough from the bay to breed and feed. The large schools offer an easy target for the pelicans as they scan the waters from above. With bones reinforced by air pockets to help absorb shock, pelicans are able to dive headfirst from heights of up to 60 feet to retrieve a meal. Throughout the summer, these gregarious birds can be seen feeding in a frenzy of diving and splashing. Only 30 years ago the survival of the brown pelican was in jeopardy, as accumulation of the then-common pesticide DDT in their tissues and eggs led to reproductive failures. DDT was banned in 1972, and the pelicans have come back stronger each year since; there are an estimated 6,500 breeding pairs in California today.
Leaving Seal Bend behind, you soon arrive at Rubis Creek. Just passable at high tide, this tidal creek meanders through a labyrinth of pickleweed-edged tidal flats. Kayaking this close to shore, it’s hard to miss the crabs and other critters that live here in the intertidal zone. They may not be as charismatic as the otters and pelicans, but they are a crucial part of this biotic community, providing nourishment for upper-level predators. The mud is pockmarked with holes revealing the presence of innkeeper worms, moon snails, and Washington clams below the surface. Paddling down this narrow creek, you may notice squirts of water from the mud as clams retreat into their burrows. One square foot of this muck can hold thousands of these invertebrates. As you make your way through, you’ll encounter numerous birds—snowy egrets, American avocets, black-necked stilts, and marbled godwits—taking advantage of this muddy feast. Eventually the creek rejoins the main channel, just east of where you started.
Sharks are another important component of the slough’s food chain. The estuarine sharks found here—primarily leopards and smoothhounds—are not as large as the great whites found out in the bay, topping out at 7 and 4 feet long, respectively. They come to the slough each spring to give birth and feed on small fish, crabs, and worms along the slough bottom. They give birth to live young who will remain in the slough throughout the summer, swimming in schools. Adults can sometimes be seen trapped in the shallows by the outgoing tide, or perhaps finning through the main channel. These sharks can also be viewed from shore, at places where you can look into the shallow water from above.
The main channel turns to the north just as it reaches the Elkhorn Slough National Estuarine Research Reserve. Once a working dairy, this 1,400-acre preserve on the east side of the slough is now managed by DFG with the help of the National Oceanic Atmospheric Administration (NOAA). The reserve, one of 25 such research reserves around the country, manages the upland hills and waterways that lie east of the railroad trestle. Although boats are not allowed in the reserve’s waters, its hills are a great place for exploring on foot and learning more about this entire ecosystem.
Just a little farther north, you’ll find Kirby Park, the only other landing site (and bathroom) along the slough. Managed by the Moss Landing Harbor District, this is a great place to start if you have your own boat. It also has the only wheelchair- and stroller-accessible trail on the slough.
From here, the main channel continues north for a couple of miles before coming to an impassable railroad trestle at Hudson’s Landing. While your kayak can go no farther, the water continues east under the tracks and past Elkhorn Road to terminate in a vast pickleweed-dominated marsh known as the Blohm-Porter Marsh. After a long summer with no rain, the pickleweed becomes saturated with salt and turns a beautiful crimson red—Elkhorn’s fall color.
- Map by .
At the north end of the slough, many of the surrounding hillsides have been protected by the Elkhorn Slough Foundation, the local land trust that owns or manages 2,500 acres in the watershed. At its helm is Mark Silberstein, known as the resident “Slough Guru.”
“This is such a biologically rich environment,” says Silberstein. “Its long-term sustenance depends on our ability to manage and balance a wide range of human uses with the fundamental requirements of healthy nature. This is our challenge—to do conservation in a working landscape.” With the good work of the foundation and others, this “cosmic center” will continue to provide a welcome and necessary refuge for its many residents and visitors, human and nonhuman alike.
Kayak launch site: Moss Landing Harbor is on Highway 1, midway between Santa Cruz and Monterey, just north of the bridge over the mouth of the slough.
Elkhorn Slough Reserve: From Highway 1, turn east at the Moss Landing power plant onto Dolan Road; follow the road for 3.5 miles, then tun left onto Elkhorn Road; drive 2.2 miles and make a left into the Reserve. From Highway 101, go two miles south past 156 East exit and turn right onto San Juan Road; follow 2.3 miles, then turn left onto Tarpey Road, which becomes Hall Road. Drive 4.5 miles and make a left on Elkhorn Road. Drive five miles and make a right into the Reserve.
Most recent in Habitats: Freshwater, Bay, Marine
Marine ecologists have long been alarmed at the potentially dangerous summertime growth of the single-celled algae Pseudo-nitzschia -- but there are still significant blind spots in our knowledge and research funding has been scarce.
El Nino | Habitats: Freshwater, Bay, Marine
How much sea foam along the shore is normal for this time of year? And how can you tell if it's harmful to marine life? We asked UC Santa Cruz oceanographer Raphael Kudela.
Ask the Naturalist | Climate Change | Habitats: Freshwater, Bay, Marine