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Current position of the SSV Corwith Cramer. Click on the vessel to view position history. Use the tools, top right, to change the map style or view data layers. Dates and times use GMT (Greenwich Mean Time).


SEA Currents: SSV Corwith Cramer

July 13, 2014

A Cookie Cutter Shark

Mary Engels, 2nd Assistant Scientist

Above: Cookie Cutter shark shows its teeth…. Below: Shellbacks new and old gather to celebrate another successful equator crossing….

Ship's Log

Position
0° 39.2’’S x 169° 36.1’’W

Location
JUST SOUTH OF THE EQUATOR

Sail Plan
Fore and Main Stays’ls and the main engine.

Weather
Sunny with a chance of squall…

Wow, what a day…  Late last night and during the wee hours of this morning the science lab kicked into gear and deployed our standard hydrocast to collect water sample from the deep.  After 1000m of wire out, the carousel came back aboard full of water and surprises.  While the hydrocast is normally a device for collecting water samples and CTD data, this particular morning, we collected another very special sample.  Caught between the lanyards that hold the niskin bottles open and the bottles themselves, we found 45 cm long cookie cutter shark.  Given the positioning of the shark, sandwiched between four bottles and four lanyards, it was clear that the shark swam through the lanyards while the bottles were cocked open. Unfortunately for the shark, once the first bottle closed, it couldn’’t get free and each subsequent bottle firing trapped the poor creature further.

Cookie cutter sharks (Isistius brasiliensis) gets its name from the way it takes bites out of prey.  Mostly cookie cutters target large fast swimming fish such as swordfish or dolphins, but they are opportunistic feeders and have been known to take chunks out of man-made objects on occasion.  The upper teeth in the jaw are used to latch onto the prey while the heavily calcified lower teeth slash out a circular piece of flesh.  During attachment on their prey they use specially adapted spiracles on the tops of their heads to continue passing water over their gills so they can breathe. They also have extensive photophores all over their body that allow them blend with and/or imitate the bioluminescent patterns of small fish, and they are known to migrate vertically over huge distances (~150 - 3,500 m depth).  Though this was a wonderful hydrocast surprise, I am not sure it is very repeatable as a standard shark sampling method!

pic

As if that excitement were not enough, we also crossed the equator today. With that crossing came the deployment of the last of our ARGO floats. Given the divergent nature of the waters surrounding the equator, it is difficult to keep ARGO floats in these regions for any length of time.  Over the course of our cruise track we have deployed a total of four ARGO floats to help fill in this equatorial gap.  Of course with the equatorial crossing there were other reasons for celebration.  As of this time, there are 18 shiny new shellbacks onboard! In keeping with the traditions of the I-Kiribati people, as well as the mariners of western history, we made offerings of food and drink to gods of the seas and thanks for safe passage across their waters.  In addition there was a lavish costume party complete with firehose showers and turtle shaped ice-cream sandwiches courtesy of Nina, steward extraordinaire. 

It is late afternoon now and in a few hours we will cross the line into the Phoenix Islands Protected Area where the real work will begin.  Until then I am going to hit my rack for some much needed sleep.  Hope all is well back on land and know that we think of you as we continue our explorations on the big blue.

So long and thanks for all the fish!!
Mary

P.S. Dear family, miss you, love you and can’t wait to see you soon. Staggle… have a safe and wonderful ALVIN dive.  I want pictures!!!  Love you too and I’’m super excited to see you when I get home.

Categories: Robert C. Seamans,Protecting the Phoenix Islands, • Topics: s254  science • (0) Comments
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