Spencer Cody: Science at Sea, June 1, 2014

NOAA Teacher at Sea

Spencer Cody

Aboard NOAA Ship Pisces

May 27 – June 11, 2014

Geographical Area of Cruise:  Gulf of Mexico
Mission:  SEAMAP Reef Fish Survey
Date:  June 1, 2014

Observational Data:

Latitude:  27˚ 50.503 N
Longitude:  93˚ 46.791 W
Air Temp: 26.3˚C (79.3˚F)
Water Temp: 23.3˚C (73.9˚F)
Ocean Depth:  126.8 m (416 ft.)
Relative Humidity:  84%
Wind Speed:  7.8 kts (9.0 mph)
Barometer:  1,009.5 hPa (1,009.5 mbar)

Science and Technology Log: 

It was not until the Pisces arrived at its first survey area off the coast of Texas that I was able to appreciate the volume of scientific data collection that this vessel could collect.  It took most of the 27th and all of the 28th to arrive at our initial survey area.  While in transit, the Pisces is constantly collecting data.  Data such as air temperature, wind direction, relative humidity, wind speed, and barometric pressure are recorded and periodically reported back to NOAA and the National Weather Service and from other marine vessels to improve data on meteorological events in the Gulf and weather forecasts.

In addition to collecting meteorological data, the Pisces uses a fishery acoustics system called the ER-60 to track depth and various sea floor features.  This system can also be used to monitor biomass such as fish, coral, and even plankton.  Once we arrived at our initial survey area within the SEAMAP survey grid, the amount of science conducted increased dramatically.  In the survey areas, the camera array is dropped to the sea floor to survey fish populations.  In most cases we are looking at fish habitat from 50 to 120 m deep.  Video and still photos are taken of fish attracted to the bait bag filled with squid.  To ensure that sampling is both consistent and unbiased for the survey, pictures and video are pulled at random from all four cameras on the camera array.  It is important that the same procedures are carried out throughout the SEAMAP survey gird concerning data collection in order to be able to reliably compare different survey areas and track species development and abundance.

In order to assist the camera array in obtaining accurate information about precisely how deep the camera array is when it is recording fish population data, a Temperature Depth Recorder or TDR is attached to the camera array to compare position in the water column to what the ship’s fishery acoustics system is displaying.  This is necessary in case the camera array has fallen off an underwater cliff or is hung up on some other topographic feature.

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The Conductivity Temperature and Depth or CTD submersible probe can measure the salinity of the water, temperature, pressure, plankton concentrations, dissolved gases, and water samples at different depths.

The Conductivity Temperature and Depth submersible aids the ship’s acoustic equipment in determining an accurate depth of the ocean bottom.  Since sound travels at different velocities in water that has different densities and temperatures, information regarding the salinity and temperature of the water must be fed into the ship’s fishery acoustics system to calibrate the system for it to accurately read the bottom depths.  If temperature or salinity are not taken into account, the depth will either be too shallow or too deep compared to the true value.

The Pisces not only has the ER-60 for fishery acoustics, but it also has a state of-the-art multi-beam echo sounder, the ME-70, that has 27 transducers that are aligned in a configuration allowing for scans of wide swaths of the ocean bottom.  In fact, the Pisces has engines that are specifically designed to run quietly enough to accommodate such advanced acoustic equipment.  The ME-70 is used for mapping various sample areas of the SEAMAP survey.

While the camera array can be used to measure the length of some of the fish viewed, it cannot reliably determine characteristics such as age or sex.  Determining age or sex just through appearance can be very tricky in the Gulf and is frequently unreliable.  Many species of fish will grow at different rates depending on available forage and other environmental factors.  This is an issue that is also commonly encountered among freshwater fish in South Dakota.  Complicating fish characteristics even further, many reef fish are one or the other sex at different phases of their lives.  They are not strictly male or female but change roles depending on complex physical or environmental factors.  With so many factors complicating these characteristics, live catches are necessary to determine the full story of what is going on with reef fish in the Gulf.

For live catches we use bandit reels.  Bandit reels are similar in concept to a standard fishing rod and reel except they are built for heavy duty sea fishing.  The reel and rod are attached to the side of the ship.  One hundred pound test line is used with a five pound sinker weight.  Each line for the bandit reels has ten hooks, a small float that keeps the hooks in a vertical column, and a large float that keeps the ten hooks just above the ocean bottom. 

  Again, in order to guard against bias in the results, we use the bandit reels with a set procedure.  For our survey we are using three bandit reels at a time each with ten hooks.  The bandit reel stations are in radio communication with the dry lab, where the chief scientist is coordinating the sampling, and the bridge, which is keeping the ship in position for the lines preventing lines from running under the ship.  Since we want to be as objective as possible without contributing to any type of bias in the sampling, each line was in the water for exactly five minutes.  Even though it may have went against every natural inclination of most fishermen and fisherwomen, we were not allowed to jig our lines or do anything that might attract more fish to our bait.  In addition to standardizing the number of hooks and the length of time spent fishing, three different sizes of hooks are used and rotated out from each bandit reel station; consequently, one of each of the three hook sizes is always being used for each survey area.

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White, nickel-sized disk-like structures called otoliths can reliably age fish. They are inner ear structures that grow in size as a fish ages allowing calcium carbonate deposits to form over the course of its life. Scientists can read these calcium carbonate deposit rings like rings in a tree to determine the age of the fish.  Credit Harriet Nash for the photo.
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After all the measurements are taken of the fish and their otoliths and gonads have been sampled, the information must be added to the database for use in the SEAMAP Survey. Credit Adam Pollack for the photo.

After five minutes of fishing, the lines are brought up and fish are tagged one through ten to keep fish identified with a specific hook and depth.  The tagged fish are then taken to the wet lab for measurement readings.  In the wet lab, fish length, weight, sex, and phase of reproductive development are recorded.  Since reproductive development, and sometimes even sex, can be difficult to determine, a sample of each fish’s gonads (ovaries or testes) are removed and placed in a labeled specimen vial for confirmation in the lab back on land.  The otoliths (inner ear bones) are removed from the fish, as well, in order to reliably age the fish back in the lab.  Once the measurements are recorded, they need to be added to the database to be compiled with the gonad and otolith specimens.  This is just a small piece of the monitoring that is occurring in the Gulf through NOAA.  The Gulf of Mexico is a remarkably diverse expanse of ocean and requires significant scientific research in order to understand and track fish populations and the habitat and forage that sustain them.  Without these types of intensive scientific studies on the ocean, we could not possibly manage or attempt to conserve a natural resource that we would, otherwise, have little to no understanding of.

Personal Log:

Since we had arrived off the coast of Texas a couple of days ago, we have been slowly back tracking to Pascagoula as we go through our survey areas.  The weather has been beautiful the last couple of days; however, sea swells do cause the boat to jostle around a bit.  Each day we see more species on the surface of the water and through our camera array under the water.  Since the science log is rather long for this post, I will talk more about life at sea and the different types of organisms we are encountering in future posts.

Did You Know?

Fish identification can be a tricky business in the Gulf of Mexico.  Many species of Gulf fish alter their physical appearance depending on their reproductive development, environmental factors, or phase of physical development.  Fish will even appear to have different patterns depending on whether they are viewed under our out of water.

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