Photos of a Great Egret foraging for Yellowfin Gobies in the shallow mudflat next to Breakwater Beach at the southeast corner of Alameda Point. After catching a Goby, the Egret would then have to fling the little fish into the air to maneuver the fish back to its mouth. Photos are from Friday, February 9, 2018.
Alameda Point’s harbor seal population fluctuates between single digits and 50 during most of the year on the specially-built harbor seal float. But when the Pacific herring arrive in the winter to lay their eggs, many more seals arrive to feast on the herring, causing a sudden spike. Last winter, a spike in seal numbers to a record 70 came on January 5, 2017, in the midst of the herring run. This winter, the herring arrived sooner, in December, and so did more harbor seals, causing a spike to a new record of 73 on Christmas Eve and Christmas Day.
In the brief time span since the new harbor seal float was set in place, local monitors have assumed that it was simply the colder water temperatures that enticed greater numbers of seals to use the float in the winter. But in fact, they discovered it’s not the full story.
It turns out that dropping water temperature indeed has an effect, but the effect is on the herring. Ideal water temperature for herring spawning is between 50 and 53.6 degrees Fahrenheit. The water temperature at Alameda Point dropped below 54 degrees the afternoon of December 16 and continued dropping another 2.3 degrees, according to data collected by the National Oceanic and Atmospheric Administration. This brought on the herring run and, in turn, the voracious seals.
The rain ended, the sun came out, and so did the harbor seals at Alameda Point. So many of them came out of the water to warm up on their new float on January 5, hardly any of the structure was visible. The number has many observers asking for a second float.
The regional ferry agency installed the new float after removing an old Navy dock used by the seals, in order to make way for a ferry maintenance facility.
“I nearly keeled over when I saw the platform,” said Lisa Haderlie Baker, harbor seal monitor and Alameda resident. “So many seals packed cheek by jowl, literally, that I had to count them four times using binoculars to make sure there were 60 of them, at least, basking in the sun, which I knew had to be close to a record. It was a tremendous thrill.” Continue reading “No vacancy on float for harbor seals”
Location, location, location! But for a fenced-off dilapidated navigation light stand on a jetty at the Seaplane Lagoon, ospreys would not have had a successful nesting season this year.
In late August two adult ospreys took flight from their Seaplane Lagoon perch for parts unknown with two healthy offspring. It was a welcome sight because for the past three years a series of frustrating avian soap operas featuring other ospreys and unwanted nesting attempts aboard the maritime ship Admiral Callaghan were marked with failure. Previously in 2012 they had raised one chick, the only other recorded case of osprey reproduction at Alameda Point.
A new concrete float for harbor seals was delivered to Alameda Point on June 22. It is the first-of-its-kind on the West Coast. With seals starting to use the new platform, a milestone has been reached culminating two-and-a-half years of citizen advocacy to maintain a resting site for harbor seals at Alameda Point. A ferry maintenance facility is slated to begin construction this summer where the seals have been finding solitude for over a decade. The new float will be anchored 300 yards away to the east.
In an effort to acclimate the seals to their new float and surroundings, the float is being moved in stages to its permanent location. It will be anchored a hundred yards offshore from the Bay Trail near the soccer field on West Hornet Avenue. Continue reading “Harbor seals adapting to new float”
Conservation of wildlife isn’t just important at Crab Cove
Visitors flock to Crab Cove, a State Marine Conservation Area, to learn about and experience the Bay’s sea dwellers. The educational lessons at the Crab Cove Visitor Center are equally relevant throughout the waterway south of the USS Hornet at Alameda Point where even more creatures thrive in relative obscurity.
The area encompasses an interconnected web of vegetation, birds, seals, fish, mollusks, crustaceans and worms. Ghost shrimp, bat rays, leopard sharks, striped crabs, mussels, California sea hares and fish with light-emitting diodes are just a sampling. A 36-foot-wide rock wall, known as a breakwater and built by the Navy in 1945, forms the mile-long southern boundary.
Ghost shrimp are seldom seen, since they spend most of their lives in tunnels constantly digging and filtering the sandy mud for nutrients. But the evidence of their presence is plain to see during low tide at the mudflat west of the Encinal Boat Ramp. Thousands of small mud mounds dotting the landscape have an opening in the center leading down into the shrimp burrow.
The shrimps’ perpetual mining and aeration of the mud makes the environment attractive to other species as well, such as the arrow goby. These tiny fish are only a few inches long and almost completely transparent. They share the burrows with the shrimp. At low tide they can be seen darting around in shallow pools of water in the sand. Occasionally least terns dive to grab a goby.
A neighbor of the shrimp and gobies is the lugworm or sandworm. They, too, are seldom seen, but at low tide their ropey casings of excavated sand and mud are a clear sign of their presence. Another sign of their presence in recent weeks are the almost clear egg sacs. At low tide they look like deflated balloons that washed ashore. But when submersed in water, it becomes apparent that the egg sacs are tethered to the worms’ tunnels. The jelly sac keeps the eggs moist at low tide.
Another seldom seen creature is the foot-long California sea hare or sea slug. Their brownish color and slow movement makes them difficult to spot, even when they venture among the rocks near the water surface. During egg-laying season, a clue to their presence is the large bright yellow clumps of eggs deposited on the rocks, which look like angel hair pasta.
Sea vegetation serves as an anchor for herring eggs. Some eggs are churned up by tides and currents during the prolific herring-spawning season and eaten by birds.
Algae and vegetation on rocks in the tidal zone serve as food for striped crabs, always busy picking away. But crabs will quickly move under a rock if they spot a visitor with one of their eyes that can be raised up out of the socket.
Armies of kelp flies walk – not fly – along the waterline on the beach during warm weather waiting for kelp to wash up so they can lay eggs.
Small fish, such as the jack smelt, provide food for the diving California least terns. Just about any size fish is prey for the California brown pelicans that hang out by the thousands on the section of breakwater surrounded by water known as Breakwater Island. Fellow marine birds the double-crested cormorants dive deep, chasing down prey by paddling their webbed feet. Mussels are a delicacy for gulls, which can often be seen hovering and dropping mussels on rocks and pavement to crack open the shell.
The strangest fish to appear in the channel is the plainfin midshipman. It can create its own light in the deep waters it inhabits during most of the year. Their skin is laced with hundreds of bioluminescent photophores that can help it attract prey, as well as emitting light that matches surrounding water to make it difficult for predators to see.
The leopard shark with its large leopard-like brown markings can grow to seven feet in length but is harmless to humans. These fish forage for food in the shallow intertidal zone going after crabs, shrimp, worms, other fish and fish eggs.
A gracefully beautiful fish and a regular at Alameda Point is the bat ray, which feeds along the bottom but can occasionally be seen swimming just below the surface.
A moon jellyfish was recently spotted in Alameda Point waters, drifting along near the surface.
Harbor seals, representing marine mammals, round out the marine life roster. Alameda Point hosts the only harbor seal haul-out in the East Bay between Yerba Buena Island and Fremont.
Originally published in the Alameda Sun.
More photos of Alameda Point marine life, with map
Three thousand tons of sand was added to the nesting grounds for the least terns at Alameda Point in late February and early March. In the weeks that followed, volunteers from St. George Spirits and the Boy Scouts and Cub Scouts came out to help make the site ready for the arrival of the terns in mid-April.
The Water Emergency Transportation Authority (WETA) paid for enough sand to cover half of the 9.6-acre nesting area with three inches of sand, as well as for grading. The weeklong delivery of sand was a conservation mitigation requirement for the impact that WETA’s new ferry maintenance facility will have on the terns’ feeding area. As many as 12 ferries will make up to four passes per weekday through the Alameda Point Channel where the terns frequently dive for small fish.
Wind and water erosion take their toll on the sand substrate lying atop old airfield taxiway pavement, requiring periodic replenishment. This latest delivery of Angel Island coarse sand has built up the sand depth on much of the site to the point that it’s starting to feel like a real beach underfoot. Beaches are the traditional nesting habitat for terns.
In March, virtually all of the employees of nearby St. George Spirits showed up on a rainy Sunday morning to help distribute cinder block grid markers and clay tile chick shelters throughout the site. The high-spirited and determined crew trudged through puddles of water determined to get the job done regardless of how wet they got. Some of the volunteers worked in the old Quonset hut repainting and numbering the plaster markers that the Fish and Wildlife Service uses to identify each nest. Others re-stenciled cinder blocks.
The cinder blocks and the plaster markers allow for systematic data collection on nesting success. The blocks and markers were removed prior to the sand delivery and grading work.
In April, Alameda Boy Scouts of Troop 73 joined the Cub Scouts from Pack 1015 for the final preparations for the least tern arrival. “Overall, 25 youth from 4th grade to 12th grade and 15 parents joined this final chilly work day putting out oyster shells, flattening the area after a week of rain and pulling the last of the weeds,” said Dorinda von Stroheim, Webelos Den Leader Pack 1015. “The kids loved placing the shells and took extra care to make sure all the shells were evenly distributed.” The scouts were supposed to get pizza delivered at noon, but they hustled through their assignments so quickly that the pizza parlor was not even open yet. They accepted a rain check from the Audubon Society.
The least terns, an endangered species, have enjoyed phenomenal success on the old airfield at Alameda Point. Pushed to the brink of extinction by human encroachment on their traditional Southern California coastal nesting areas, the terns began taking up residence on a number of military bases in California during the past four decades. With early and continued stewardship by the Navy through 2014, and the addition of volunteers after the base closed, the Alameda Point colony went from a few nests to over 300 today.
During the 2015 nesting season, the Alameda Point terns were the top performers statewide, both in terms of the total number of fledglings produced, and the key data point — ratio of fledglings per nest — according to recently released data.
The public is invited to see the terns during the annual “Return of the Terns” event on June 18. Tours by bus leave from the Crab Cove Visitor Center after an educational presentation. Reservations are required for one of the three tours via the visitor center, or the East Bay Regional Park District’s website https://apm.activecommunities.com/ebparks using the search keyword “terns.”
Originally published in the Alameda Sun.