Spring in Monterey Bay

March 16, 2013  •  Leave a Comment

Each spring, the Monterey Bay National Marine Sanctuary plays host a series of spectacular natural events as the cycle of birth and death plays out for its inhabitants.  Monterey Bay is a wide bay along the central coast of California, bisected by the largest and deepest submarine canyon in the Pacific.  This canyon draws deep pelagic water within a few miles of shore and generates the forces that lie at the base of these annual events.  The Monterey Canyon begins at Moss Landing, located at the middle of Monterey Bay and extends about 95 miles out into the Pacific Ocean ending in the Monterey Fan nearly 12 000 feet below the surface.

Sea otter eating a crab

Near the town of Moss Landing, the Elkhorn Slough is one of California’s largest wetlands winding in seven miles from the shoreline.  This reserve provides an important resting and feeding environment for a large variety of animal life including more than 340 species of birds.  The tidal marsh contains wading birds such as the black necked stilt and long-billed curlew which probe below the surface for aquatic invertebrates.  Larger birds such as egrets search for fish in the shallows while song birds like the red winged black bird perch from reeds.

Long-billed curlew

Trips into the bay typically begin from further south in the city of Monterey.  From the boat docks at Fisherman’s Wharf boats travel out into the heart of the bay.  In these protected waters around the wharf, marine birds such as the Pacific loon paddle around and harbor seals sun themselves on exposed rocks.  Leaving the wharf, boats pass the breakwater covered in young male California sea lions and nesting Brandt’s cormorants.  In the springtime.  During the breeding season, Brandt’s cormorants develop a bright blue gular pouch below their bills which are unique amongst cormorants and fade quickly after the nesting season.  These cormorants are colonial nesters.  The male stakes out a nesting site and seeks to attract a female to it.  In attracting the female, the male cormorant performs an elaborate dance involving exaggerated wing postures and twisting of its neck.  Once paired up, the male and female cormorants will construct a nest made from seaweed, eelgrass and algae gathered from the surrounding waters.  The male gathers the supplies while the female builds the nest.  The nesting site is then protected by the pair acting in unison against surrounding cormorant pairs and even giving much larger sea lions a painful nip if necessary.

In the waters around the breakwater, sea otters dive for molluscs, crabs, and other small prey.  Molluscs are opened by smashing them against stones held on the otter’s belly as it slowly swims on its back.  Adult sea otters are the heaviest members of the weasel family but they are small for marine mammals leaving them particularly vulnerable to predators.  As a result, the otters prefer the protected waters of the marina or the kelp forests that lie close to shore.  In the spring, some female otters can be seen carrying their small babies on their bellies as they swim.  The sea otters gain protection from the cold from an exceptionally thick fur coat which is the densest in the animal kingdom.  This coat traps air and the resulting buoyancy is too much for the young babies to overcome so they can not dive under the water.  When danger approaches, the mother otter will grab the baby by the scruff of its neck and pull it under the water with her.  This buoyancy also allows the mother to leave a sleeping baby floating on the surface while she dives for food.

Sea otter protecting her baby

Around the corner of the breakwater, rafts of California sea lions bask in the water, regulating their body temperatures in the cold water by elevating a flipper above the surface to capture the warm sun rays.  While they rest along the breakwater and rocky shores, these sea lions hunt for fish out over the edge of the deep submarine canyon.  Depending on food availability, the sea lions may hunt alone or in large groups.  These groups provide a degree of protection to help watch out for predators such as transient orcas and white sharks that hunt these waters.  Out over the canyon, the sea lions can dive deep into the cold water slowing their heart rates to allow them to remain submerged for up to ten minutes before surfacing for rest and air.  The sea lions are often seen alongside whales, dolphins and sea birds hunting cooperatively on the large schools of bait fish.

Each spring and summer, bait fish thrive in the waters near the canyon as a result of the forces of upwelling.  Upwelling occurs when surface waters are heated by the sun and water layers stratify into warmer surface and cold deeper waters.  Winds blow the warm surface water offshore at a 90 degree difference to the prevailing wind and current direction due to the effects of the earth’s rotation.  As the warm, nutrient poor surface water is blown offshore, cold water rises from below carrying sediment up from the bottom.  The sediments carried by the cold water upwelling provide nutrients to phytoplankton resulting in blooms that feed zooplankton which are in turn eaten by small fish.  As a result, giant schools of small fish populate the waters over the canyon attracting larger predators.  

The first animals you tend to notice at the feast are flocks of pelagic birds.  Amongst the smallest birds in these mixed flocks are the red-necked phalarope.  These phalaropes are small waders which typically feed in shallow waters.  However, unlike most waders, they can also be found feeding in deep pelagic waters in areas of upwelling such as the Monterey Canyon.  Almost all of the non-breeding season is spent in the open water.

A medium sized bird, the sooty shearwater is found in large numbers in the waters over the Monterey Canyon.  These amazing birds breed mainly around small islands in the southern oceans and follow spectacular long-distance migrations, traveling in a circular route around entire ocean basins.  Shearwaters breeding in New Zealand may travel more than 45 000 miles in a year averaging more than 300 miles per day.  They do not make these incredible migrations in a flock but rather as single individuals that associate with other migrants only opportunistically.  When flying over the water, the shearwater dips from side to side on stiff wings with few wing beats and wing tips almost touching the water.  The shearwater is an accomplished diver, reaching depths of up 220 feet in search of fish and squid.  They most commonly take surface food but will often follow diving whales to catch fish disturbed by the leviathan.

Sooty Shearwater

Much larger is the black-footed albatross with its two to three foot long body and an impressive wing spin of up to seven feet.  The black-footed albatross breeds on mid-Pacific islands and spends the non-breeding season along the Pacific coast of North America.  During the non-breeding months, these birds usually stay at least 12-18 miles off shore feeding in pelagic waters.  It mostly eats the eggs of flying fish as well as fish and squid and to a lesser extent crustaceans.  It typically scoops up its food from the surface of the ocean relying on flying fish eggs which are easier to locate on the surface during the day.

Another larger surface feeding bird, the Western gull, is also common in these Monterey feeding groups.  Like the albatross, the gull is unable to swim or dive below the water surface and depends on food available to its reach from the surface.  The gull is a large and aggressive bird which helps to make up for its inability to dive.

In addition to the large groups of pelagic birds and sea lions hunting along the canyon, a variety of dolphin species may be seen in the vicinity of the canyon or on the trip out from Monterey.  Two of these dolphin species, the northern right whale dolphin and Risso’s dolphin, have unusual appearances.  The northern right whale dolphin along with its southern cousin are the only dolphins that completely lack a dorsal fin resulting in a sleek, hydrodynamic, torpedo shape.  The northern variety has a striking color pattern of mainly slick inky black with a white ventral patch that runs along the underside from front to back.  There are also smaller white patches on the tip of the rostrum (front) and on the undersides of the flippers.  The northern right whale dolphin is highly gregarious, usually living in groups of 200 but up to 2000-3000 and often joining with other dolphin species in large mixed pods.  The northern right whale dolphin is seen most often in cool, deep, offshore waters where they mostly feed on squid and lantern fish, although a variety of surface and midwater fish are also taken.

Risso’s dolphins are robust and stocky with a bulbous head and no beak.  At birth, a Risso’s dolphin is uniform light grey in color but as the animal ages it darkens and accumulates numerous scratches and scars from the beaks of squid and from the teeth of other Risso’s dolphins resulting from their typically rough and physical social behaviors.  These dolphins feed mainly on squid, crustaceans and occasionally small fish.  Risso’s may be found singly but tend to form small pods.  Like other dolphins, Risso’s can form very large groups and will occasionally be found with other dolphin species in mixed groups.  They have a cohesive social structure of multiple generations that stay together for extended periods, however, in the larger schools, segregation by age and sex is seen to occur.

Risso

A third species of dolphin that is commonly seen is the Pacific white-sided dolphin.  These acrobatic dolphins have a robust body, short beak and a beautiful, sleek black, white and grey coloration with a long light colored stripe.  These animals are extremely playful and social with a love for bow riding and somersaulting in the wake of passing boats.  They feed on squid and small fish such as sardines and herring.  While hunting they are capable of diving for 6 minutes or more at a time and work cooperatively to herd fish.


As all of these avian and mammalian predators converge on the shoals of schooling fish over the canyon the sight is magnificent.  Large whales lead the parade with smaller sea lions and birds following their path both above and below the water to snap up fish disturbed by the whales.  The humpback whales arrive in Monterey bay in the spring after migrating from their winter calving grounds off Mexico where the mate and have their young.  The southern calving grounds are relatively nutrient poor and these whales arrive each year to the rich waters of Monterey Bay in order to feed.  Their feeding combines deep dives to several hundred feet deep where prey is often concentrated to lunge feeding for surface prey.  These 50 to 55 foot long whales often lead the assault on schools of small fish with a trail of diving birds and sea lions following under the water and other groups of birds following along the surface.  These large whales are also very active at the surface with a variety of spectacular behaviors including breaching, pectoral slapping, tail lobbing and spy hopping.  Many of these behaviors produce tremendous noise in the water and likely serve at least in part to signal other acoustically associated humpbacks in the area.  When the humpbacks are less focused on feeding they occasionally demonstrate curiosity towards boats swimming around and under boats while rubbing their skin against the hull and extending their huge, often barnacle-encrusted, pectoral flukes.

Spring also brings migrating grey whales through Monterey Bay.  These whales over winter in the lagoons of the Baja Peninsula and Mexico where they mate and calves are born.  In the early spring, the adult males leave first on the epic migration north, up to 7000 miles, to the Bering Strait of Alaska.  The females with calves leave later taking advantage of the extra time to nurse their growing calves in order to build their strength and to train the calves in necessary skills for the long and dangerous migration ahead.  For most of the migration, the whales follow the coast line using kelp beds to play and hide their young from predators.  However, when they reach Monterey Bay and its deep submarine canyon, the mothers and calves are forced to choose between cutting a shorter route across the canyon or taking the long, but safer shallow route around the bay.  Without the kelp beds and shallow waters to disguise the calves from listening and echolocating orcas, the calves are vulnerable.  Perhaps it is orienting or inappropriate vocalizations from the inexperienced calf that draws the hunting orcas in.  Transient orcas of California also return to Monterey Bay each spring to hunt the vulnerable and inexperienced calves.  When grey whale calves are not available in the bay, the orcas hunt seals, sea lions and small dolphins and porpoises.  In years when few grey whales are born, the sea lion population of Monterey Bay can be hard hit.

Killer whale (orca) chasing a seal

The same individual orcas are seen in this area each year and generations of their young participate in the hunting and killing of grey whale whales bring the skill set to the next generation.  Most attacks occur at the canyon edge.  If the mother grey whale detects the hunting orcas early enough she may flee with her calf to shallow water where the orcas appear unwilling to follow.

Attacks on adult grey whales are relatively rare with most attacks focused on isolating, battering and drowning the calf.  The mother grey whale protects her baby by attempting to place her titanic body between the calf and the attacking orcas and helps the baby to breath and rest between assaults by rolling on her side or back and holding the calf out of the water. However, the attacks are relentless lasting up to 5 hours or longer and the young calf is eventually separated from its mother where it is drowned or dies from a combination of internal and external wounds.  Upon dying the calf’s body sinks.  To some extent the orcas can hold the body up or drag it up from the depths in order to feed.  The tongue is usually torn out and large strips of fat rich blubber are pulled from the dead whale.  Orcas can dive down as much as 1000 feet to feed on a carcass.  Like a pack of wolves, the orcas are highly social and their is a lot of social contact and play after a successful hunt.  Tail lobbing, breaching, and even sexual displays are common in this setting.

Killer whales (orca) after a kill

As a dead whale descends into the deep water it delivers many tons of nutrients to dark regions of the abyss.  The Monterey Canyon is part of a larger, complex system of canyons extending out into the Pacific.  The greater Monterey Bay Canyon System consists of the Monterey, Soquel and Carmel Canyons.  Soquel Canyon joins Monterey Canyon about 11 miles seaward of the canyon head near Moss Landing at a depth of nearly 3300 feet.  Offshore, eighteen and a half miles southward down the canyon Monterey Canyon joins Carmel Canyon at a depth of 6463 feet.  At the head of Monterey Canyon near Moss Landing at depths of less than 6500 feet, the canyon and its tributaries tend to have steep walls and narrow floors.  The relatively flat floor is about 820 feet wide with a slight seaward slope and steep walls which average between 10 and 25 degrees but may be as steep as 35 degrees in places.

Animals that live in this harsh environment are specialized to survive in conditions of tremendous pressure and low oxygen.  Water temperatures reach about 40º F (4º C) and the pressure is 320 times the air pressure at sea level.  The deep sea is also dark with some fish, jellies and squid specialized to produce their own light while others have small eyes or none at all.  The canyon walls are inhabited by pink and white soft corals that live in 650 to 4000 feet of water using flowery tentacles to grab prey drifting by in the water column.  This is also the environment where deep sea sunstars quickly move about grasping anything it can catch with its 22 arms as well as long-legged spider crabs and predatory tunicates that resemble a submarine venus flytrap.

In the mid water, below 450 feet sunlight never penetrates and no solid surfaces exist.  a variety of strange deep water fishes hunt this region and demonstrate a daily vertical migration approaching the surface at night.  This nightly migration is probably the greatest migration of animals in the world.  The canyon floor is inhabited by a variety of sharks and their strange relatives the chimaera with their rabbit like faces and extremely ancient ancestry.  Most of the whale is eaten not by larger animals such as sharks or even by the orcas themselves but rather by smaller, more bizarre animals such as hagfish and polychaete worms.  Two such worms are specialized to digest bone.  Nothing is wasted as each specialized species takes its turn.  Although most of the food fall is not so large as this, the inhabitants of the deep depend on the “nutrient snow” that falls from the surface above.

Thus, even as life is cut short for the young whale it showers life giving nutrients onto the typically food poor sea floor which in turn supports the surface with the upwelling which provides the foundation of the surface food pyramid.  So, as life gives way to death and provides for others, spring gives way to summer bringing the ocean’s greatest inhabitant to Monterey bay with the arrival of the blue whale.  And so it continues in one of nature’s greatest and least understood places.
 


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