Dawn White: Pinging for Populations, June 29, 2017


 

NOAA Teacher at Sea

 Dawn White

Aboard NOAA Ship the Reuben Lasker

June 19 – July 1, 2017

 

Mission: West Coast Sardine Survey

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

Date: June 29, 2017

 

Weather Data from the Bridge

Date: June 29, 2017                                                         Wind Speed: 7.7 kts

Time: 6:15 p.m.                                                                 Latitude: 4805.5N

Temperature: 12.7oC                                                      Longitude: 12520.07W

 

Science and Technology Log

The technology present on this ship is amazing and at the same time quite overwhelming.  These systems allow for data to be collected on a wide range of variables both continuously and simultaneously.  Below are a couple of photos of the acoustics room where multiple sensors are monitoring the feedback from sonar systems placed below the ship’s hull.  One of the acoustic probes sends out sound waves in a cone-like formation directly below the ship.  Another unit emits sound waves in a horizontal pattern.  The ship was designed to run as quietly as possible so as to not disturb the marine life present in the waters as the ship passes by and also to reduce the interference of the ship’s sounds with the acoustics feedback.

 

 

Acoustics technician Dan Palance managing the multiple computers that are constantly collecting data.

Multiple programs help to eliminate the “noise” received by the probes until all that remains are images that represent schools of fish and their location relative to the ocean floor.

 

The images above were taken from a poster on board the Reuben Lasker. They illustrate the range of the water column surveyed by the various acoustic systems.

 

The “soundings” are received by the ship, processed and “cleaned up” using a series of program algorithms. The image below shows the feedback received from one of the systems.

Displays of feedback from an acoustics system

Once the background “noise” has been eliminated, the resulting image will show locations of fish, school size, and the depth (y axis) at which they can be found.

Graph of acoustic feedback, with background “noise” eliminated, depicting depth and size of fish schools

 

Extension question for my students reading this:  Approximately how deep are the schools of fish being picked up by the sonar at this location?

Acoustics aren’t the only tools used to try pinpoint the locations of the fish schools.  As I wrote about on an earlier blog, the CUFES egg sampler is used to monitor the presence of fish eggs in the waters that the ship passes over.  Water samples are analyzed every half hour.  If egg samples appear in an area where there is also a strong acoustics signal, then that may be a location the ship will return to for the night’s trawl.  The main focus of this trip is to monitor the anchovy and sardine populations, so extra attention is paid to the locations where those eggs appear in the samples.

Personal Log:

Each time we drop the net for an evening trawl it is always retrieved with a bit of suspense:  What’s going to be in the net this time?  How big is the haul?  Will we capture any of the key species or haul in something completely different?

I can honestly say that while on board there were no two hauls exactly the same.  We continued to capture large quantities of pyrosomes – unbelievable amounts.  Check out the net-tearing load we encountered one night.  We literally had to weigh them by the basketful!

Here I am getting ready to help unload this large catch.

TAS Dawn White prepares to help unload large catch

 

Net-tearing load of pyrosomes!

Above is the codend of the net filled with pyrosomes and fish.  A 5-basket sample was pulled aside for analysis.  The remainder was simply classified and massed.

While I was certainly don’t need to see another pyrosome any time soon, there were plenty of other times when some very unique species made an appearance!

Pacific Jack Mackerel

Solitary Common Salp

TAS Dawn White holds a Blue Shark

Dogfish Shark

Did you know?

The dogfish shark (pictured above) was one of about 50 or so that were caught in the same haul.  We had trawled through a school that was feeding on the small fish found at the ocean surface during the evening hours.  This is the same species of shark that is commonly provided to students for dissection.  Use the search terms “dogfish shark dissection” and see what you find!

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