Dawn White: Otoliths & a “Wet” Farewell: July 2, 2017


NOAA Teacher at Sea

 Dawn White

Aboard NOAA Ship Reuben Lasker

June 19 – July 1, 2017

 

Mission: West Coast Sardine Survey

Geographic Area of Cruise: Pacific Ocean; U.S. West Coast

Date: July 2, 2017

Weather Data from the Bridge (As in back home in North Branch, MN)

Date: July 2, 2017                                                             Wind Speed: 8 kts

Time: 7:30 p.m.                                                                 Latitude: 45.5102° N

Temperature: 26.7 oC                                                     Longitude:  92.9931° W

Science and Technology Log

It wasn’t until the last day or two of my leg of the research project that we finally started to catch the species the scientists were specifically looking to track and even then there were only a few.

Angela removes an otolith from the sample target species

Here’s Angela dissecting one of our first samples.  If the young captured were either sardines or anchovies, they were massed, length taken, sex determined (including whether or not they were sexually mature, if possible), and their otoliths were removed.

So what the heck are otoliths and why would anyone want to remove them?

Otoliths are small, bony parts of a fish’s earbones.  They help the fish with balance and orientation.  These bones are made of calcium carbonate and similar to the formation of rings on a tree, they grow with a ring-like pattern based on seasonal metabolic rates.  While the fish is growing faster during the warmer summer months, the rings are broader and more translucent.  Then, during the cooler winter months when a fish’s metabolic rate begins to slow down, that part of the ring appears to be more dense or opaque.

Look at the first illustration below that was taken from a 2008 NOAA press release.  On the lower right you see an image of an otolith from a haddock.  Each species has otoliths of a particular size and shape. If you know the region of ocean from which a set of otoliths was obtained, you may be able to determine the species by utilizing one of the many otolith references that can be accessed online, such as found in this memorandum published by NOAA researcher Mark S. Lowry.

 

The enlarged image on the right was taken from the NOAA Images Library.  Here you can see the rings very distinctly.

Extension question for my students:  Using the otolith image on the right, determine how old the fish was at the time of capture.  Not sure how to do this just yet?  Want to test your accuracy?  Read up on what is involved in the study of sclerochronology first. Then test yourself with this otolith aging interactive.  Enjoy!

Once the otoliths have been removed they are wiped clean and placed in a small vial to finish drying out.  The otoliths are cataloged and sent to the lab for evaluation as shown in the photos below.

 

The combination of measurements taken allow those studying the population to look at the demographics of the catch (What % of the population is juvenile?  What % is sexually mature? What is the relationship between % male vs. female?).  This data provides a sampling of the population’s health and viability, which can then be extrapolated to the population as a whole.  This information can then be used to help inform policy with regards to how heavily these populations can be fished without causing damage to the ecosystems of which they are a part.

 

Personal Log – It’s time to go home!

It seemed like we had just gotten started and it was time to go!  Although they had mixed work/sleep schedules, the science team was willing to gather to see me off.

Angela, Dereka, Dawn (TAS), Nick, Amy, Bryan, Sue, Emily

What an amazing learning experience!  My only regret was that we didn’t start to find the species requiring the more intense, time-consuming dissection and data collection until the very end.  I wanted to make sure I was doing my part!  In return, what I get to take home to my students is invaluable. I can’t wait to share all I have learned about life aboard a research vessel, the many ways in which this unique habitat is being studied, and the vast opportunities that await those who are interested in marine ecosystems.

The only travel plan that was not prearranged regarding my TAS adventure was the exact location of my departure from the Reuben Lasker.  What I did know was that it was to be a “wet transfer.”  What I didn’t know was exactly what that meant.  It was so much fun finding out!

The Reuben Lasker has a limited number of ports along the west coast where it is possible for it to dock.  The ship’s size, unique keel, and specialized, below-ship sonar equipment require channels to be much deeper than many smaller ports possess.  Because of this, whenever there is to be an exchange of personnel made before a larger port is reached, an onboard transfer craft brings those getting off to a smaller port along the way.  This allows the main vessel to stay in safer waters much further off shore.  Once the exchange of people and gear is made, the transfer boat returns to the ship and the journey continues.

Unique points to consider on this type of trip, however, are that you need to get the transfer boat launched from the main vessel, the ship lets you off several miles from port, and the boat has no seats – you stand up the whole way!  Who knew that even getting back to the mainland was to be an adventure?!

You can see the transfer boat below (right side in the picture – port side of the ship).  Notice how the Reuben Lasker carries it hoisted up off the floor of the back deck.

View of the transfer boat (at right) stored on Reuben Lasker

The transfer boat gets lowered to deck level so we can all step in.  Our gear is stored in the open bow and we all load in the back.  Behind the center console are poles with handles that give us something stable to hold on to as we will be standing for the duration of the trip.  We all wear life jackets and hard hats as the boat is lowered along-side the main ship.

Here’s Skilled Fisherman Victor Pinones ready at the controls as he lowers us to sea level.

Skilled fisherman Victor Pinones ready at the controls

The two outboard motors are started while we are along-side so we are ready to move away from the Reuben Lasker the minute we hit the water.  And we’re off! To give you some perspective of the size of the Reuben Lasker as it looks from the water, you can see Emily, Angela, and Dereka waving to me from the Level-1 deck.

View of NOAA Ship Reuben Lasker from the transfer boat

It didn’t take long before the ship was but a spot on the horizon….

Here’s a better look at the transfer vessel as crew members prepare to for the return trip.

Bon voyage to all!  Safe travels!

Did You Know?

Fun fact: Baby squid are adorable!  Just had to share one last image from under the microscope – thanks, Nick, for pointing this out!  At this larval stage, the squid are mainly transparent except for their developing eyes and chromatophores (sac-like structures filled with pigments that help the squid undergo color changes).  You can observe this process in action at the Smithsonian’s  Ocean Portal web site.

 

Looking at the enlarged photo at right you can just make out the scale – our little friend was a whole 3 mm in diameter!  Too cute!

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