Originally published here:
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
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
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
"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."