Tuesday, June 16, 2015

Nudibranchs in the Tidepools

Nudibranchs, also referred to as sea slugs, can frequently be spotted in the tidepools at Haystack Rock. There are many species of nudibranch, most having outstanding markings and colors. The nudibranch feed on bryozoans, hydroids and sponges and it's color can be changed by the food it eats.   The nudibranch has a pair of sensory projections on their head, called rhinophores, which allow them to smell and taste. Virtually all nudibranchs have some form of eyes but they are not well developed and in most cases are little more than a pigment spot in the head near the rhinophores.  The nudibranch breathes through gill projections which extract oxygen from the seawater. The Pacific Northwest has more than 200 species of nudibranchs.

The Opalescent Nudibranch (Hermissenda crassicornis) could be called 'showy'. It is found from Alaska to Baja, California and can grow to two inches in size. At Haystack Rock, it can be found in the sandy bottom of a tidepool. It is slender with numerous gills (called cerata) that are orange with white tips. There is typically an orange area of the back that is bordered in blue, although the colors may vary.

Opalescent Nudibranch 

Opalescent Nudibranch with aggregating anemone

The Rufus Tipped Nudibranch (Acanthodoris nanaimoensis), on the other hand, is not nearly as showy as the Opalescent. This nudibranch has a white or gray body that is covered with projections with yellow tips, except for the gills which have red tips. It lives in the low intertidal zone and typically grows to just over 1 inch long.

Rufus Tipped Nudibranch

 Other Recent Sightings at Haystack Rock

Pile Worm (Nereis vexillosa)

Ochre Sea Stars (Pisaster ochraceus)

Purple Shore Crab (Hemigrapsus nudus)

This weekend will be eventful one on the sands of Cannon Beach; the 51st Sandcastle Contest is Saturday, June 20th. On your way to the sand creations, make sure to make a stop at Haystack Rock and discover the inhabitants of the tidepools for yourself! HRAP Interpreters are on the beach every day at low tide and are happy to point out the tidepool dwellers and answer your questions!

Tuesday, June 9, 2015

Tracks in the Tidepools

Hermit Crabs have curved abdomens which are soft, unlike most crustaceans which have hard, calcified abdomens. Because of their soft abdomens, the hermit crab is vulnerable to predators and seeks protection in the form of salvaged, empty seashells. The hermit crab will typically select the shell of a sea snail into which its entire body can retract for protection.

Hermit Grab in the Tidepool
Photo Courtesy of Carolyn Propst

As you might guess, as a hermit crab grows it gets too big for its salvaged shell and must look for a larger one. The competition for shells can be vigorous when there are lots of hermit crabs of the same size vying for an available shell. When the hermit crab finds a new shell it will leave its current shell to 'try on' the new shell. If it fits, it will stay in the new shell leaving the old shell for a smaller hermit crab to make the shell its home. If it doesn't fit, the hermit crab returns to its shell and continues the quest for a empty shell that is the perfect fit!

Tracks in the tidepools are a great way to find a hermit crab. As the crab moves along the sand it will sometimes leave a track in the sand - if you follow the track to the ends the hermit crab is bound to be at one end or the other!

Hermit Crab Tracks in the Sand
Photo Courtesy of Carolyn Propst

Next time you are tidepooling at Haystack Rock, take some time to look for a track that is sure to lead to the discovery of a hermit crab. HRAP Interpreters are on the beach every day at low tide and are happy to answer any questions you might have!

Wednesday, June 3, 2015

Black Oystercatchers Need Your Help!

The birds continue to be active at Haystack Rock. Today, the Black Oystercatchers take center stage! Oystercatchers have been seen mating and are nesting on the Rock.

The Black Oystercatcher (Haematopus bachmani) is a large (about the size of a crow) and noisy bird that makes its home along rocky shores from Alaska to Baja California. It is a wading bird, black in color, with a long, red bill, yellow eyes that are outlined in red, and tan colored legs. They feed primarily on mussels, limpets and other shellfish; foraging mostly near low tide and resting at high tide.  When feeding on mussels, found in abundance on Haystack Rock during low tide, the bird either finds a slight opening in the shell, inserting its long, red bill into the opening to feed or the bird will hammer on the shell to open it.

Black Oystercatcher, August 2014
Photo Courtesy of Susan Glarum

The Oystercatcher nests well above the high tide line and near a food source such as mussel beds. The nest site is typically on either gravel, a grassy area, or a depression in rock. The nest is built by both parents and can be lined with pebbles or bits of shell. Typical clutch size is 2 to 3 eggs that are pale tan to olive in color with brown and black spots. Both parents take turns guarding the eggs during the 24 - 29 day incubation period. The nesting pairs at Haystack Rock can be seen swapping guard duty at the nest.

Black Oystercatcher, August 2014
Photo Courtesy of Susan Glarum

After hatching, the parents continue to guard the young near the nest. As the chicks grow, they follow their parents to the feeding areas and are fed by them there. The young can fly at around 5 weeks but will stay with the parents until they can feed themselves. 

The area around nesting Black Oystercatchers at Haystack Rock are closed during low tide to protect the birds and give them the greatest chance for survival. The overall success for the species, both for egg hatching and survival of the young, is relatively low; closing the immediate nesting area helps to increase the survival odds. 

Black Oystercatcher Nest 
Closed at Low Tide to Protect the Site

We hope to see you on the Beach soon ... and perhaps you will see the Black Oystercatchers guarding their nest and, when hatched, guarding and feeding their young. Bring your binoculars or visit the scopes set up near the Rock at low tide to watch the Oystercatchers from a distance that won't endanger them.