Bioluminescence, Part 2

Bioluminescence is produced by a chemical reaction similar to the one that happens when a glow stick is broken. This reaction releases energy as light. The color of the light that is produced is usually blue or green, but can be red, yellow, or orange, depending on the chemicals used in the reaction. Most animals produce only one color of light, but some fish and worms use two colors of light

Looking for fish beneath cliffs of Laird's Sandstone on Tomales Bay
Photo by Casey Newman, 2011, All Rights Reserved.

Some animals, like fish and shrimp, use photophores, or special organs to produce light. Others, such as jellyfish, have specialized cells scattered over their bodies that glow. Certain species of organisms play host to bioluminescent bacteria, which produce light in exchange for room and board. There are some species of squid that produce bioluminescent ink, which is squirted out as a defense mechanism.  Single celled organisms such as bacteria and dinoflagellates use special compartments in their cell to separate the chemicals that react to produce light, combining the compartments when necessary.

At depths of between 200m and 1000m in the ocean, up to 90% of animals use bioluminescence to blend in with their surroundings. The light that reaches down into those depths is blue-green, and these animals will use bioluminescent photophores (cells or organs that produce light) to match the amount of blue-green light around them, camouflaging themselves.  Other fish that live at those depths produce red light. Many organisms that live that deeply cannot see red light, so the fish that produce it can use the light to see their prey without being seen.  Deeper in the ocean, where conditions are always cold and dark, animals do not need bioluminescence to blend in, but they do use it to attract prey and for communication and courtship. These animals have unique patters of photophores, which may help them to recognize others of their species.

Plainfin Midshipman Fish
Photo copyright Terrence J Fidler, 2006,robots4farms.com

One type of bioluminescent fish, called the plainfin midshipman fish, lives deep in the Pacific Ocean but migrates to the coast in the summer to lay their eggs. These fish are a type of toadfish with no spots or stripes on their dorsal fin. Their photophores are arranged in a U-shape on the underside of their body, and the photophores look like the buttons on a naval officer’s uniform, which is how they get the name midshipman fish. The photophores are used to blend in with the light around them while they are in the ocean, which keeps predators from seeing them from below.

The male midshipman fish returns to Tomales Bay first, digging out a nest in the rocks along the shoreline. The rocks at Nick’s Cove are a favorite spot for these nests. Once there, the males begin to hum to attract females. The hearing of the female midshipman fish is so accurate that they can tell the difference between each male’s hum and find the nest of the hum they like best. Once there, the female will lay her eggs and return to the open ocean. The males fertilize and take care of the eggs, continuing to hum until their nests are full of eggs from many females. The males guard the nest until the eggs hatch and the hatchlings are ready to be on their own.

To hear the plainfin midshipman fish’s hum, visit Discovery of Sound in the Sea: http://www.dosits.org/audio/fishes/plainfinmidshipman/.

East Pacific Red Octopus on Tomales Bay

All Rights Reserved Tressa Bronner

Recently, we had a chance to get out onto Tomales Bay on a beautiful sunny afternoon. It was a great day for paddling as well as viewing wildlife. We saw all kinds of tide pool creatures, harbor seals and seabirds. Our most exciting find, however, occurred as we were launching our kayaks into the bay. Just as the first couple of boats paddled away from the ramp, we began to see long, shiny red tentacles emerging out of the water. Soon after, the head and body of a rather large East Pacific Red Octopus followed as the handsome critter slowly and carefully made his way onto shore. Undoubtedly, our stomping around in the mud launching our boats disturbed him from his cool, shady hangout; but it gave us a great chance to check out one of the bays most interesting bottom dwellers up close as he shifted from red to purple to brown.



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The East Pacific Red Octopus, once thought just be the young of North Pacific Giant Octopus, is its own species entirely. These much smaller cousins of the Giant Octopus only grow to be about 20 inches from the top of their head to the end of their tentacles. Like all octopi, they are capable of changing their color, generally ranging from red to brown and occasionally white. While the Giant Octopus is found in the depths of the ocean, East Pacific Reds prefer the warm shallow waters of bays and estuaries.

Unlike other invertebrates, when the East Pacific Red catches a meal, it does not eat it right on the spot. Instead, it gathers a collection of crabs, clams and scallops and brings them home to enjoy at its leisure. When the meal is done, the octopus carefully stacks the empty shells outside the entrance to their home, giving the other animals roaming the bay a clear idea of who lives there.

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In general, the Octopus is thought to be one of the most intelligent of all invertebrates. Research has shown that they are capable of problem solving and retaining memories. In fact, the East Pacific Red Octopus was the first invertebrate in captivity to show signs of having individual personalities.

Obviously in our rush to get out onto the water we had disturbed the little guy from his normal routine; so once we were finished taking his picture, we helped him find his way into the shade under the dock and out of sight of the hungry seagulls flying overhead.

Tule Elk in White Gulch

Tule elk are found only in the grasslands and marshlands of California and are the smallest species of elk in North America.

The Bulls...

While sitting in the kayaks in White Gulch we can hear a beautiful ominous call coming from the surrounding hillsides. The Tule elk are in rut and the bull elk are bugling to attract females to their harem and to ward off potential competing males.

Bulls can be distinguished from the females during the mating season by their antlers. In the spring antlers are covered with velvet, a system of blood vessels that nourish the bone as it grows. A set of elk antlers can weigh over 40 pounds. Older bulls have more points, but they do not grow a point for each year of age. Antlers are used as weapons by the males to compete for the chance to breed. Two evenly matched bulls may use their antlers in combat, if other attempts at intimidation (vocalizations and posturing) have failed.

A bull that has proven himself bigger and stronger than the others defends a harem of up to 30 females. This means he is the primary bull, responsible for 80% of the breeding. Towards the end of the breeding season other secondary bulls may get the opportunity to breed as the primary bull tires.

Males are sexually mature at age two, but usually aren't able to breed until they are strong enough to compete with other bulls to defend a harem of cows. Half the the male population will remain bachelors; most breeding is accomplished by ten percent of the male population.

The Ladies...

Female elk are sexually mature by two years of age, although they may be able to breed as yearlings. Females are gathered into harems by dominant males.

While the males fight for real estate and mating rights to the harem, the females do their own bit of fighting for status within the harem. Almost all female elk will reproduce, having on average, six to ten calves in her lifetime. Calves are born after an 8.5 month gestation period. They nurse for four or five months, but start nibbling on grass when they are less than one month old. The calves remain part of the harem with their mother.

Leopard Sharks in Tomales Bay and Drakes Estero

Leopard Shark. Photo by Kambiz Kamrani. 2005

The easily identified Leopard Shark is often encountered in our waters near Point Reyes, often when paddling near them in our kayaks on tomales Bay and Drakes Estero. But it is in the turbid estuarine environment where this attractive little hunter really shines. Paddling around in June and July we often see the water roiling about with tails and fins as these beautiful fish find mates and give birth.

Leopard Sharks do not rule these murky waters uncontested. They share estuaries with, among other, Shovelnose Guitarfish, Bat Rays, and the Brown Smoothhound Shark. The Leopard Shark and Brown Smoothhound are closely related and would be expected to be competing for the same resources. A study looking at the feeding habits of the Leopard Shark and the Brown Smoothhound in San Francisco Bay found that both species feed predominantly on shrimps, crabs, and fishes, but that Brown Smoothhounds hunt predominantly in rocky intertidal areas while the Leopard Shark tends to feed more in muddy areas of estuarine waters.

Leopard Shark at Point Dume. Photo by Heal the Bay. 2008

Leopard Sharks have a richly varied diet and employ several predatory tricks to secure their meals. Some Leopard Sharks feed heavily on Fat Inn-Keeper Worms, which are forcefully sucked from their U-shaped burrows. Others mutilate burrowing clams by nipping off their fleshy siphons (breathing tubes which stick out of the mud), completely ignoring the rest of the critter. When feeding on circling, densely packed schools of anchovies, Leopard Sharks have been reported to circle in the opposite direction with their jaws open, snatching up the small fish that crash right into their mouths. Their adaptable feeding behavior and appetite for several different species, undoubtedly contribute to their success.

"Jaws" Leopard Shark. Photo by Kambiz Kamrani. 2005

The Facts:

Size: At birth, Leopard Sharks are 7-8 inches. At maturity males are 28-47 inches, females are larger, 43-51 inches. The maximum recorded length is 71 inches.

Reproduction: Males mature at 7years, females at 10 years. They are ovoviviparous, meaning that they give birth to live young that have hatched from eggs within the body. The gestation period is around 12 months, at which point they give birth to 4-30 pups alternate years.

Diet: Juveniles mainly eat shore crabs. While adults have learned a scattered diet of small fish, rock crab, worms, clam siphons, and fish eggs.

Habitat: Leopard sharks are found in and around estuaries, sand bars, rocky reefs, kelp forests and especially like pliable muddy bottoms where food can be found and pried out easily.

Depth: Intertidal, literally inches deep, to about 300 feet.

April Showers, Flowers, and Sunshine

Springtime in Point Reyes is keeping the hills green. Beautiful weather followed by showers have kept the grounds lush and provided swells of wildflowers.  The peninsula is covered with colors as new flowers pop up daily. Checkerbloom, lupine, iris, poppies, blue eyed grass, and pussy ears color the green hillsides.

             

Walk out to Kehoe beach in a sea of mustard's brilliant yellow, or walk out to Chimney rock to a kaleidoscope rainbow of color dotting the path.  Gray whales are still being seen on their northward migration. A few lingering elephant seals are starting their molt.  Kayaking on Tomales Bay has been phenomenal, as the bay is teaming with wildlife. Harbor seals and their pups can be seen on Hog Island and swimming in the bay. Rafts of migratory waterfowl are foraging and resting, some here just for a break before continuing on, others stopping for the summer.

Plenty to see and do, the question right now is rain or shine? Bring your rain coat and your sunscreen and have a great time.Call us today to plan your next great adventure. Point Reyes Outdoors 415.663.8192

White's Gulch 2/4/09

Well, 'round the Hog we went. It was a short morning adventure, as we had to be back before lunch, and a gorgeous day on Tomales Bay greeted us. Today the group was high school students from SF, a teacher, and myself, the guide. The fog lifted leaving blue skies with white clouds streaking over the bay. Out on the bay there were rafts of buffleheads, a few red breasted mergansers, a pair of loons, and some brown pelicans with their mating colors. The moon jellies were everywhere in the water beneath us, their translucent purple seen below the surface. We stopped on the western side of Hog Island to stretch our legs and have a snack. The tide was low enough to see aggregate anemones, sea urchins, limpets, chitons, and both bat stars and ochre stars. As we started back towards our launch site we were followed by a harbor seal who kept popping up on either side of our group. All in all a good wildlife day paddling on the bay.

For more info: http://www.pointreyesoutdoors.com/WhitesGulch.htm