Freshwater Sunfish: Common name for members
of the family Centrachidae, comprising numerous species of
spiny-finned, freshwater fishes with deep, laterally flattened
bodies found in temperate North America. All members of the family,
which includes the black basses (genus Micropterus ) and the
crappies (genus Pomoxis ), prefer fertile lakes with firm bottoms
and build nests, which the males guard pugnaciously. The sunfishes,
or breams, genus Lepomis, are smaller ( 1/4 lb/.14 kg average)
members indigenous to E North America but successfully introduced in
the West. Common eastern varieties are the rock bass, the bluegill
and green sunfishes, and the long-eared and common, or pumpkinseed,
sunfishes, brilliantly colored with bright orange bellies. The
redear and warmouth sunfishes are found in the Mississippi basin;
the spotted sunfish, or stumpknocker, is a denizen of the South. The
Sacramento perch is the only native western sunfish. The black
basses, the most important and valuable of American freshwater game
fishes, are longer bodied and larger (averaging 2-3 lb/.9-1.4 kg);
they include the largemouth and smallmouth black basses and the
spotted bass. The crappies are the largest sunfishes, attaining a
length of 1 ft (2.5 cm) and a weight of 2 lb (.9 kg). There are two
species, the white crappie ( P. annularis ) and the black crappie or
calico bass ( P. nigro-maculatus ). The pigmy sunfishes, rarely over
1 1/2 in. (3.8 cm) long, bear an uncertain relationship to the
family and are classed separately. The totally unrelated ocean
sunfish, or headfish, Mola mola, of the family Molidae, is allied to
the puffer . Sunfishes are classified in the phylum Chordata ,
subphylum Vertebrata, class Osteichthyes, order Perciformes, family
Centrachidae.
Ocean Sunfish: The ocean sunfish,
Mola mola, is the largest bony fish in the world. It is a unique
pelagic fish, and specimens of ocean sunfish have been observed up
to 3.3 m (11 ft) in length and weighing up to 2,300 kg (5,100
lb).[1]
A member of the order Tetraodontiformes, the ocean sunfish has many
derived characters and is the type species of its genus.
The ocean sunfish feeds on jellyfish and other gelatinous, soft
bodied zooplankton, as well as small fish and other marine life.
Physiology
The ocean sunfish is described as a flat, oval fish with grooves on
its body. It has a rounded 'tail' known as a clavus instead of a
caudal fin. The short, broad clavus is formed by extensions of
dorsal and anal fin rays. It is wavy, with eight to nine ossicles
and 12 fin rays. The ocean sunfish has rough, sandpapery skin
covered with mucus. Its average weight is one ton and its average
length from the tip of the snout to the tip of its clavus is 6 ft
(1.8 m). Vertically, from fin to fin, its average size is 11 ft (3.3
m). The ocean sunfish is taller than it is long and has large, high
dorsal and anal fins, which are dark in color. Its tiny mouth cannot
be closed and its top and bottom teeth are fused to form a beak. It
has a round, bulging eye, and its skin is extremely thick and
elastic. There is a distinct line at the posterior where denticles,
scales, on the skin change from extremely rough to very fine. Its
pectoral fins are small, fan-shaped, and pointed upwards. It has
four gills and a slit behind the last one is covered by a thin flap
of skin near the pectoral fin called an operculum.
Ocean sunfish.Because of its very short and stiff body, it has no
more than 16 vertebra, and the spinal cord is under 15 mm long (less
than 0.5 in). A specimen of 200 kg may have a brain no bigger than a
nut. The fish's unusual shape results from its unique development,
in which the tail does not grow with the rest of the body. As the
rest of the body grows to the enormous adult size, it 'wraps around'
where the tail would normally be, giving the squared, 'cut-off'
shape of the adult mola tail.
Juveniles are silvery in color and adults are usually dark gray to
white, with variations in mottling and spots. Ocean sunfish are
usually grey above, silvery grey to brown on the side, and paler or
dusky below; some individuals are brown. It is able to change color
rapidly from spotty to even-colored.
Though unrelated, ocean sunfish are commonly mistaken for sharks, as
they often swim close to the surface and have dorsal fins that
protrude from the water, similar to the dorsal fins of sharks. They
are found in warm and temperate zones of all oceans, including the
eastern Pacific and the eastern and western Atlantic. There are
three to five species of Mola.
Fins
Like the triggerfishes and pufferfishes it is related to, Mola mola
uses its long, thin dorsal and anal fins for propulsion; it lacks a
caudal fin (or 'tail fin'), having in its place a rudder-like
structure, the clavus. Its fry resemble miniature pufferfish, having
spines, a hint at the species' place in the evolutionary tree. The
ocean sunfish uses its dorsal and anal fins to "scull." This
behavior is described as a way to propel the fish, allowing it to
swim forward by moving its dorsal and anal fins from side to side.
The mode of swimming utilized by the Mola mola can be described as
Tetradontiform, in which they use oscillations of their dorsal and
anal fins to propel themselves through the water.
Toxins
While the flesh of the ocean sunfish is considered a delicacy by
some, it contains neurotoxins similar to those of other poisonous
tetraodontiformes.
Diet
Ocean sunfish eat jellyfishes, salps, comb jellies, zooplankton,
squid, and crustaceans. They live in the Eastern Pacific and
Atlantic. Despite the soft and watery nature of their food, it is
densely packed with proteins, vitamins and minerals, and occurs in
vast swarms. This, and the mola's huge appetite, is the reason why
molas can grow larger than any other bony fish. Their predators
while smaller are orcas, Sea Lions, dolphins and marlin. Orcas are
the only likely predators of large adults.
Reproduction
Molas can produce more than 300 million eggs, each about 2 to 3 mm
in diameter, more than any other known vertebrate.
Life
They are thought to live for over 10 years. Interestingly, the rough
and leathery skin (a fibrous tissue up to 15 mm thick) of the ocean
sunfish is host to more dermal parasites than that of any other
marine creature.
Behavior
Ocean sunfish are generally thought to be solitary fish, swimming
freely in the ocean alone. However, certain sightings of molas in
groups of more than ten have been reported. Juvenile ocean sunfish
are said to socialize and gather in schools.
Sometimes molas are spotted floating sideways on the sea surface.
Although most scientists are still puzzled at this behavior, it is
commonly thought that they are basking in the sun, not sick or
unhealthy. Some observers have seen sea birds such as gulls picking
ectoparasites off basking ocean sunfish which is another plausible
explanation why the mola would float on the surface. Some observers
have seen mola flip over onto its other side after the gull has
picked off its parasites, giving the bird a chance to have more
food, and the mola a chance to have the bugs picked off of its body.
Breaching has also been observed. Molas also seek drifting kelp in
search of small fish to remove their abundant parasites.
Environmental adaptation
Size of ocean sunfish compared to humanThe ocean sunfish uses its
clavus as a rudder and may also steer with its ability to spit
strong jets of water out of its mouth or gills. It sculls and is
propelled by waving its dorsal and anal fins from side to side and
is a weak swimmer. It usually lets the current carry it. The water
supports its enormous weight and its great size gives it safety. Its
thick, leathery hide also protects it because it is made up of
collagen fibers up to 6 inches thick. It often protects it from the
stinging jellyfish, which it eats. Its top and bottom teeth are
fused to form a beak and it also has claw-like teeth in its throat,
which are used to help it break up its food before it reaches its
stomach. The function of its operculum is to keep parasites out of
its body. It has a mouth that is perfect for slurping jellies and
salps. Like most fish, it is lighter colored on the bottom of its
body and darker above for better camouflage. The ocean sunfish's
unique ability to suck and spit water with its mouth helps it while
feeding. The mola sometimes spits jets of water in the sand to
search for food. It also sucks and spits jellies to tear them apart
and make them easier to consume with its small mouth. The ocean
sunfish has also reportedly used its ability to spit water out of
its gills to squirt sea birds, which sometimes land on the mola's
side while it is basking.
Range
Depths of up to 1,800 feet (549 m) in temperate and tropical waters
worldwide. They stay in primarily open waters, but are often viewed
near kelp beds.
Sightings
The sighting by scientists of 19 ocean sunfish in a two hour period
off the south-west tip of Cornwall in July 2006 has been cited as
evidence of the increased temperature of British waters.
An ocean sunfish was also sighted by Mr Richard Harrison and Mr Jim
Harrison aboard their private craft off Port Eynon Headland on the
Gower Peninsula in Wales on the 26th August 2006. The fish was
swimming within 1/2 a mile of the shore with its dorsal fin
protruding from the surface. Upon further investigation the ocean
sunfish was approximately 4feet long and looked to be alone.
A dead ocean sunfish was sighted floating in the River Tay, Scotland
in the vicinity of Broughty Ferry on Saturday 2nd September 2006 by
members of the Tay Sail Training Association and 5 members of the
Ralfs Family. The ocean sunfish was approximately 1 to 1.5 metres
long.
A 'basking' ocean sunfish was spotted near Port Quin, Wadebridge,
Cornwall UK on Monday 25th September 2006 by John Willacy whilst sea
kayaking below cliffs.
A dead ocean sunfish measuring 3.3 m long and 3.2 m high was
collected off the coast of Whangarei, New Zealand in November 2006.
It is believed to be the largest sunfish ever found with a weight of
around 2.2 - 2.3 tonnes.
One specimen of sunfish was seen Sunday, February 2009 of the coast
of Zamboanga, Philippines. Measuring 2.3 meters long, 1.3 meters
wide and weighing one tonne. The giant sunfish appeared to be weak
while it was beaching off the coast, however it died on Sunday.
Local marine biologists have stated that due to its weakness it
could have been washed ashore. An on-going autopsy is being carried
out to determine the cause of death.
Conservation notes
Ocean sunfish are sometimes caught accidentally in drift gillnet
fisheries. They make up nearly 30% of the total catch of the
California drift gillnet fishery for swordfish, outweighing the
number of swordfish caught. Most sunfish are released alive, but
many of the released fish show obvious signs of trauma, including
abrasions, bleeding and gill discoloration from air exposure.
Reducing bycatch of non-target species is becoming a priority in
fisheries management.
Another threat to ocean sunfish are floating plastic bags which look
like their natural prey, jellyfish. Sunfish can choke as they try to
swallow the bags, or slowly starve as the plastic clogs their
stomach. People can help protect these animals by picking up plastic
bags at the beach and properly disposing of trash.
Name
The ocean sunfish is also known as the marine sunfish, pez luna, the
moon fish, or simply by its specific name, mola (Latin for
"millstone", which it was said to resemble because of its grey
color, rough texture, and round shape). It has various obsolete
binomial synonyms; its original name was Tetraodon mola.
The freshwater sunfishes (family Centrarchidae) are unrelated; for
other fishes known as "sunfish", see sunfish.
Source: Columbia Encyclopedia, Sixth
Edition, Copyright (c) 2009.
Source: Wikipedia.org, Copyright (c) 2009.
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