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Fish, Fish and MORE Fish!
April 3, 2000
By Dr. Dan Fornari and Dave Murline (1st Mate on RV Melville)
This morning, we were busy towing the DSL-120 sonar
along the last line of our initial survey over the East Pacific
Rise near 3° 20N (check out the slide show to see
a three-dimensional bathymetric model of the seafloor that Uta
Peckman has been working on). The axis of the mid-ocean ridge
in this area actually splits into two ridge crests that overlap
by about 26 kilometers. Our analysis of the sonar data over the
past two days suggests that an area near the tip of the southern
ridge, near the western margin of the basin between the two ridge
crests, may be where the new lava erupted about four years ago.
This area is right along the line where the earthquake events
recorded in the AHA data are located.
At about 2000
hours, we brought the sonar fish back on deck, and the Deep Submergence
Operations Group team started detaching the fiber optic cable from
the DSL sonar system so that is can attached it to the Argo II
photographic and imaging system which we plan to use tomorrow to
collect images of the seafloor. While this is being done, we are
going to send a rock dredge down tonight to collect some lava samples.
The rocks should help us to see whether the lava has been recently
erupted. If the lava is very glassy that would be a good indicator
that it is young.
Early
this morning, the water surrounding the ship was a layer cake of fish.
Seriously! About 10 meters down, there was a big school of tuna of different
species. Just below the surface, there was a large school of Mahi Mahi
(dolphin fish). The icing on the fish layer cake was a large
school of flying fish and squid, jumping and trying to escape being breakfast.
I have never seen such a sight! Many members of the crew and even the science
party had a chance to fish, and just about everyone caught a fish. The Daves (Murline
and Grimes) caught dozens between them and have us well-stocked with fresh
fish for the next few days. Dave is an expert fisherman and knows a lot
about all the fish in this area. He wrote some basic information about
all the different types of fish that were caught this morning so that you
could learn more about them.
*Dave
Murline's Fish Facts*
Dolphin Fish
(Coryphaena hippurus)-- also known as Dorado or Mahi
Mahi. They grow to 90 pounds and over 6 feet in length. They are pelagic fish,
which means they live in the open ocean rather than in coastal areas.
They live worldwide in temperate to tropical waters warmer than 65°F.
They feed on flying fish, squid and crustaceans. They are known for their
acrobatic fighting -- jumping several times in order to spit the
hook when they are caught. They are a beautiful turquoise blue and
yellow when swimming in the ocean, but they turn green and gold when
hooked, and then they fade to blue gray as they die. The ones we caught
were probably around 1 year old and weighed 5-15 pounds. They are excellent
to eat when fresh, but spoil rapidly.
Skipjack
Tuna (Euthynnus pelamis)-- also known as Skippies or Aku.
They grow to 30 pounds and 3 feet in length, and live for about 7 years.
They are pelagic fish, and live worldwide in temperate to tropical
waters warmer than 68°F. They feed on bait fish, sardines, anchovies,
squid, and crustaceans. They are named for the way they feed on the
water by skipping over the surface. Skipjack are good barbecued when
fresh, and they make great sashimi (thin slices of raw fish) and fish
jerky (thinly sliced, salted and dried fish). They are also commonly
used in low-grade canned tuna or as cat food. Skippies are usually
caught incidentally when hunting for other species of tuna, but they
are fun to catch. The Skipjack Tuna we caught were probably about a
year old.
Yellowfin Tuna (Thunnus albacares) -- also
known as Atun, Ahi, or Allison Tuna. They grow to 450 pounds and 6 feet in length.
They live worldwide in pelagic waters that are warmer than 70°F. They grow
rapidly; the ones we caught were probably only 1-2 years old and weighed 5-10
pounds. By the time they reach 4 years old, they will be 150 lbs! These fish
are highly prized table and game fish. They are known for their endurance in
fighting. It is common to fight the bigger fish for several hours before getting
them into the boat. They are named Yellowfin because the second dorsal fin on
a fully grown fish is long and bright yellow.
Big Eye Tuna (Thunnus obesus) -- also known
as Gorilla tuna. They grow to 435 lbs and reach up to 7 feet in length. They
are usually caught by long liners fishing at water depths of 200 feet or more.
That is because Big Eye feed at these deeper depths, while most other tuna feed
on the surface. We probably caught them because the lights on the ship at night
attract squid and flying fish that the Big Eye like to eat. They also feed on
small fish called Mactophedes, anchovies, sardines, and crustaceans, particularly
krill (which are shrimp-like organisms). Big Eye look very similar to Yellowfin
Tuna. They live for 7-8 years and grow rapidly. They are delicious to eat, either
cooked or as sashimi (raw), and they have bright pink flesh that looks like steak.
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