A red-tailed hawk catches a hot summer thermal above. Live oaks, madrones and crackling dry grass cover the hills dotted with farmhouses. Below the hills, the Elkhorn Slough meanders in and out of the canyons looking more like a shimmery inland lake than a saltwater estuary. Off in the distance are the twin towers of the Moss Landing Power Plant and the ocean, five miles due west from here, is but a foggy memory. But there are sharks in these waters. Plenty of them.

Which is what has attracted the Santa Cruz-based Pelagic Shark Research Foundation (PSRF) to this spot on the Elkhorn Slough Reserve in Moss Landing, one of the stateīs last remaining coastal saltwater estuaries. "The presence of the energy plant is obvious," says Sean Van Sommeran, executive director of the Foundation. "What happens under the murky water is more subtle. But we have an ongoing shark and ray factory going on here. We are eagerly looking into this."

For the last 13 years the foundation has been conducting research on the sharks and rays, or elasomobranchs (sharks, rays and skates as they like to call them in shark circles) in the slough. Seven species of sharks and rays—bat rays, shovelnose guitar fish, round stingray, leopard shark, gray smooth-hound and brown smooth-hound—inhabit the waters of the slough. The research team is hoping to learn more about the essential role these predators play in the ecosystem of the estuarine habitat, and how they are using the slough for reproductive, foraging and migratory behaviors.

Across one finger of the slough, the shark research team, made up of volunteers and college students handpicked and trained by the foundation, has set up a 150-foot net. To the side is a long pole stuck in the mud to measure the rate of the outgoing tide. The mud is viscous enough to suck the shoes off your feet. Thatīs why the team wears booties and wetsuits, which make them look like gaunt seals, all 20 of them this day, wading about in the water. Their attire is also useful in countering the cold water and protecting them from the rare possibility of stepping on a bat ray, an animal that can deliver enough sting to put a researcher in the hospital.

The instant the net rattles, one of the team members, stacked out along the net, takes a large floating bin filled with water and extracts the shark from the net. After the bin is full, the researchers scuffle through the mud to a holding tank near the shore.

There the animals are tagged and noted with their gender, length and width, time, date and location of capture, and clasper (scientific lingo for shark penis) length for males, and species. Afterwards the researchers walk away from the net, bent over the water with the sharks and rays in their hands and release them.

Today, they are mostly catching thornback rays, a primeval-looking animal that is straight out of the fossil record. The muddy brown thornback looks like a hybrid of a shark and ray, with three rows of sharp little spikes that run from its head to its shark-like tail; hence the name. This animal cruises the shallow tidal flats in search of innkeeper worms, crabs and small fish, grinding them with a row of non-menacing teeth.

But thatīs not all the thornbacks are doing here. Most, if not all, are female, and many of them pregnant. Last August foundation member Matt Gardner found a dead thornback and dissected it. "There were eight, essentially miniature versions inside," he says holding up a live thornback to a group of curious nature walkers who have gathered near the shore. It appears that the slough serves as an extensive maternity ward for the female thornbacks. But like a lot of natural mysteries of the deep, and not so deep, the research is proving that answers generate a lot more questions about these complicated, highly developed animals.

The Elkhorn Slough wasnīt always this full of life. Thirty years ago plans were in place to dredge the slough and build a port and an oil refinery. Dams held back the tidal flows for farmers and ranchers looking to reclaim more land (another reason to wear booties in the mud because of the enduring barbed wire), and when the rains came, loose topsoil spilled into the slough, filling up countless acres. In fact, this particular area that the researchers are sampling and tagging sharks once was grassland.

Now, much of the slough is making a comeback. The Elkhorn Slough Foundation and the Elkhorn Slough National Estuarine Research Reserve now protect sensitive areas important to sharks and rays—not to mention birds, sea otters, harbor seals and plants. This, despite the close proximity to a large power plant, now run by Duke Energy, at the base of the slough.

(The foundation has been monitoring any ecological fallout from last monthīs fire when a gas tank exploded at the power plant, sending black smoke into the air for miles around. So far, any negative effects from the fire have yet to be determined.)

Yet, in other examples of changing environmental attitudes, sharks and rays were once slaughtered in the slough. Beginning in the 1940s the sharks and rays were hunted in an annual shark derby. Armed with hooks, pitchforks, shotguns, dynamite and bows and arrows, sportsmen hunted in the shallows, aiming to receive prizes—such as an outboard motor—for the most sharks and rays killed. Van Sommeran used to explore and play in the slough when he was a child and witnessed many of the shark derbies.

"When it was all said and done, there would be these big, fly-covered piles of sharks and rays," recalls Van Sommeran. "I remember standing in the empty parking lot and staring at all these sharks. It was obvious, even to an untutored kid, that it wasnīt a cool thing."

Years later, through the foundationīs early efforts, along with, Earth First!, Green Peace, Surfersī Environmental Alliance and others, the killing spree came to a halt in 1996.

But the sharks continue to be harmed in less obvious ways. Bottom sediments tend to archive pollution, and the foundation has found evidence of contamination in shark samples. The sharks eat organisms contaminated by pesticide and fertilizer run-off from adjacent farms, and hydrocarbon pollution deposited by the power plant, even though the plant is now operating more cleanly on natural gas. In conjunction with UC Santa Cruz, the foundation did a study on leopard sharks and found pesticides, PCBīs and chlorines in the sharks.

As for the future, the foundation plans to continue the established long-term monitoring project for years to come and hopes to expand their understanding of the sharks and rays, which includes education and conservation efforts.

"[The slough is] an assembly area," says Van Sommeran. "There are different pockets and estuaries of this slough system that are very important for very specific generational categories of the sharks and/or reproductive states. Regardless of their abundance or activities in the broader open areas like the ocean, they need to come back here to replenish. We need to protect that."