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Introduction:
The 8th Grade Class at Phoenix Country Day School traveled to Santa Catalina
Island to conduct different scientific research projects. The island is
part of the southern Channel Islands located approximately 21 miles off
the coast of California. Our research question was, what are the top predators
of the Channel Islands, why do they inhabit and hunt in the Channel Islands,
and how are they affected by human impact? Our team undertook several
procedures to access the information hidden in the kelp forest. First,
we went on a series of 4 snorkels and along the way we collected data
to get a better understanding of the environment in which our predators
live. In the kelp forests of the Catalina Islands, lurk the most impressive
and fearsome predators of any kelp ecosystem in the world. These include
the Blue Shark (Prionace Glauca), the Great White Shark (Carcharodon Carcharias),
the Leopard Shark (Triakis Semifasciata), the Pacific Angel Shark (Squatina
Californica), and the Killer Whale (Orcinus Orca). Our data collection
techniques included depth measurements, water turbidity samples, and Roving
Diver Fish Counts. We plotted our data points on special Global Positioning
Satellite units. This research paper will detail the information gathered
on our predators and the techniques used to answer the research question.
Our methods and materials were similar to many professional scientists’ procedures. To get a better understanding of the kelp forest environment we needed to collect simple and accurate data. By taking depth measurements, using a simple weight and rope, we found that the average depth at a range of about 150 ft. off the coast was 30 ft. This is the maximum depth at which kelp forests can survive. Where kelp forests grow fish are found. Where there are fish, there are predators. Using secchi disks and dropping them to the bottom, we also recorded the water turbidity. The average turbidity there was clear; you could see the weights hit the bottom at 30 ft. For kelp to grow, sunlight is needed, and in order for kelp to have sunlight, the water turbidity needs to be low. On our last snorkel we carried out a Roving Diver Fish Count in order to see the abundance of our predators’ prey. For example we recorded schools of anchovies ranging in number from 100 to 250 anchovies per pack. Our methods and materials gave us a better understanding on why and where these predators live and hunt in the Channel Islands. However, before we could fully understand the details of our study question, we needed additional background information on our predators.
Research
and Results:Throughout the world, Kelp forests are somewhat rare.
The Kelp forest occurs as a result of one simple process of nature, called
upwelling. Upwelling is caused by coastal winds. The horizontal movement
of the wind pulls the cold, nutrient rich water from the depths of the
ocean, and layers it over the warm surface waters. Kelp forests thrive
in nutrient rich water. Then, the kelp forest acts as a foundation because
it protects and creates a habitat for all of the other animals. The kelp
forests attract small fish, which attract bigger fish, and which finally
attract major predators. All of the predators we studied live in the kelp
forest for one reason prey. Many fish and other marine animals also live
in the kelp forest, because they too, can thrive off of the other smaller
fish which live in their same ecosystem.
The
first predator of the kelp forest is the Blue Shark. The Blue Shark is
about 10-12 feet in length. It is characterized by its bright, metallic
blue color, sleek body, and pointed fins and snout. It has elongated caudal
fins to provide swimming power. It is a pelagic species, which means it
likes to swim in open water. The Blue Shark will rarely venture closer
than 100 ft. to the surface of the water. This shark also likes temperate
locations throughout the tropics. Other sources say that the Blue Shark
lives primarily off shore in epipelagic areas, which is an area that is
close enough to the sunlight, for photosynthesis to occur. In cool waters
however, Blue Sharks will enter kelp beds. “Cool waters” primarily
means water temperatures between 45° F to 69° F. This shark will
eat virtually anything, but prefers squid, and carcasses of marine animals.
They will also eat schooling fish such as anchovies, sardines, herring,
and other fish such as gill netted salmon. It is probably the most graceful
shark of the Channel Islands.
The
Great White Shark is on average 14-16 ft. long. It is characterized by
its conical snout, pitch black eyes, a heavy, torpedo shaped body, and
a nearly equal lobed tail fin that is supported on each side by a keel.
The keel is the part of a fin that is used to keep the shark stable. This
shark prefers shallow, cool, coastal waters. They will rarely come into
water shallower than 100ft., and the deepest recording of a Great White
is 4,200ft. The Great White Shark’s habitat ranges from inshore,
offshore, enclosed archipelagos, near islands, and near sea lion rockeries.
During the winter, Great Whites will migrate into deeper water. These
sharks will eat any marine mammals, but prefer whales, porpoises, and
seals. They will also eat fish, turtles, squid, and crustaceans. All of
these preys are found in the Catalina Kelp Forest, but Great White Sharks
are rarely sighted. It is probably the most feared shark of the Channel
Islands.
The
leopard shark can reach up to 7ft. in length. They are characterized by
their short, broadly rounded snout. The first dorsal fin of this shark
is moderately large, the second is nearly as large, the anal fin is smaller
than the second dorsal fin, and the pectoral fins are triangularly shaped.
The skin of this shark has dark saddle shaped dots, and their upper body
is a bronze-gray color. These sharks usually inhabit waters less than
30 ft. deep. Other sources say that the leopard shark will inhabit water
ranging in depth from 12ft. to 300 ft. They prefer rock strewn, and sandy
bottom oceans. During the winter, they will migrate from inner bays to
outer temperate coasts. The diet of the leopard shark consists of a variety
of fishes, crabs, clams, shrimps, mollusks, worms, crustaceans, and fish
eggs.The
diet of the leopard shark may vary due to the seasons. It is probably
one of the most beautiful sharks in the Channel Islands.
The
angel shark can reach up to 5ft. in length. It is characterized by its
sluggish, inactive behavior, and it has no anal or dorsal spines. It often
likes to bury in the sand. The angel shark prefers to stay at the bottom
of shallow waterbeds. They will live in depths 10ft. to 600 ft. They live
in temperate coasts, near kelp or rocks, or offshore near shallow bays.
The diet of this shark consists of squid, sea cucumbers, halibut, juvenile
sea bass, and surfperch.
The
killer whale, or orca, can reach up to 25 ft. in length and weigh up to
16,000 lbs. It is characterized by its long, sleek body, black and white
skin, and large protruding dorsal fin. The killer whale inhabits cold,
nutrient rich waters where upwelling occurs. Although killer whales can
be found in both the, open ocean and coastal waters, they primarily inhabit
the continental shelf in waters less than 650ft. deep. Killer whales will
also live at any depth, and any location, as long as there is a food supply.
Their diet consists of small schools of fish, squid, octopus, large baleen
and small prey, sea turtles, otters, sharks, rays, deer, moose, tuna herring,
and any mammal that ventures too far into the open water. Also, they will
eat marine mammals such as sea lions, seals, and other whales. The killer
whale is probably one of the major predators of the Channel Islands.
To
get a better understanding of how these predators are affected by people,
we researched several books and websites. We learned that over 25 species
of sharks inhabit the Channel Islands. These sharks and other predators
play a specific and important role in the Channel Island’s ecosystem.
If these predators became extinct because of human interference, it would
offset the Channel Islands aquatic ecosystem. Human beings can have a
huge impact on sharks. Pollution off the coast of Los Angeles has negatively
impacted the kelp forest ecosystem. If the prey of these predators died,
then the predators would also die. The coastal pollution includes trash,
oil, and other chemicals. Because of the mass production of greenhouse
gasses, global warming could have a huge effect, not unlike El Niño.
El
Niño is changes of the ocean-atmosphere system in the tropical
Pacific having important effects for weather around the world. Among these
effects is increased rainfall across the southern tier of the U.S. and
in Peru, which has caused destructive flooding, and drought in the West
Pacific, sometimes associated with devastating brush fires in Australia.
El Niño events wipe out the kelp forest’s phytoplankton.
This phytoplankton is the pedestal of the food chain, acting as a firm
base for their already fragile ecosystem. This is important because phytoplankton
acts as a “Keystone Species,” which means that it keeps the
aquatic ecosystem in check.
Over
fishing is also a big concern in the Channel Islands. There are numerous
shark fisheries located off the coast of California. Sharks fished off
the coast of California are worth about $25 a pound. This brings in a
huge profit for fisherman. Today there are limited regulations and penalties
against shark fishing, which worsens the problem of over fishing of some
of these top predators. Some sharks in the Channel Islands have been put
on the endangered list. Currently about 75 types of sharks are on the
endangered species list. Over fishing poses a huge threat to the marine
sanctuaries surrounding the Channel Islands.
Sharkskin
is another reason why these marine animals are in high demand. Sharkskin
can be used as a substitute for sandpaper. It is also used as fine leather
that is in high demand in the US, Europe, and Russia. The leather is used
in expensive shoes, handbags, and wallets. Sharks teeth are used as jewelry
and the great white shark’s jaw can be sold for as much as $1,000.
One of the new scientific phenomenons is that sharks produce a chemical
in their body that attacks cancer cells. Scientists can only examine how
this works in a lab.
After
researching and studying the different predators of the Channel Islands,
we were able to answer the original research questions. The blue shark
prefers deeper and cooler waters. In Catalina, we were not fortunate enough
to see these blue sharks, but our CELP instructor informed us that the
sharks can only be seen farther out from bay. The blue shark also likes
open waters, and epipelagic waters. We found that blue sharks do indeed
like open waters because they are found offshore. They are epipelagic,
because they are part of the kelp ecosystem, which is located at a depth
where photosynthesis can occur. Blue sharks are also said to eat anchovies,
sardines, and herring, which we saw in Catalina. There is no additional
negative impact of humans on blue sharks other than the damage caused
by pollution and over fishing.
The
Great White Sharks numbers are very few near Catalina Island, and therefore
we were not able to observe any. Based on what we found in My World Project,
the prey of the Great White Shark is for the most part located in the
northern part of the Channel Islands. Therefore, we did not see many whales
and porpoises at Howland’s Landing. As for the human impact on Great
White Sharks, they are hunted because of the danger to people.
The
leopard shark was very abundant near Catalina Island, and they were seen
on almost every snorkel. From our data, we stated that the leopard shark
lives inshore in shallow waters. This was absolutely true, because we
saw these sharks about 5-10ft. from the shore line. Leopard sharks also
swim in water depths of 12ft. to 300ft. We found in Catalina that some
were found in water less than 12ft. deep. Leopard sharks swim on the coast
of Catalina Island because of their prey, which consists of fish, clams,
and crabs. We saw all of these marine animals on our snorkels. The written
data we researched on the leopard shark matched the actual data we collected
in our field observations.
We
did not observe any angel sharks, and we believe the reason for this has
to do with this shark’s diet. In our snorkeling excursions the only
prey of the angel shark that we observed was the sea cucumbers. If there
is not an abundance of the prey, most likely, the predator will not be
nearby. Although, angel sharks do inhabit the Channel Islands, they are
not generally found near the coast of Catalina, but one was sighted by
an instructor near Indian Rock.
The
killer whale was not sighted near Catalina Island, and we were guaranteed
not to see them. From our My World Project we found that killer whale
sightings progressed upward through the Channel Islands and into the northern
California coast. Once again, we believe this occurs because the prey
of the killer whale is also located in the northern Channel Islands. Also,
cooler temperatures, and deeper waters is a major factor of why killer
whales are located in the north. Killer whales are hunted because their
commercial value in blubber, oil, and other body parts, is worth a great
deal of money.
Conclusion: We learned much about our research question while we were in the lab at PCDS and during the time we spent at Catalina Island. Predators of the Channel Islands play a major role in the island ecosystem. Because of the growth and abundance of kelp and the existence of prey, the environment is perfectly suited for the predators, which inhabit the Channel Islands. At an alarming rate, these fascinating and wild creatures are disappearing right in front of our eyes. To protect these species we need to understand them. We should always protect these rare species of predators so that our children and all future generations have a chance to observe and research these mysterious and almost perfect creatures of Earth.
