David Knight: Scup and Grouper and Grunt, oh my!, July 10, 2018


NOAA Teacher at Sea

David Knight Aboard NOAA Ship Pisces

July 10-23, 2018

Mission: Southeast Fishery-Independent Survey

Geographic Area: Southeastern U.S. coast

Date: July 10, 2018

Weather Data from the Bridge:

Latitude: 34 34.2’

Longitude: 76 56.6 W

Sea wave height: 0 – 1 ft

Wind speed: 7 kts

Wind direction: 230

Visibility: 10 nm

Air temperature: 29.8 C

Barometric pressure: 1011.9

Sky: Few clouds

Science and Technology Log

Today we set off on our two-week fishery survey off the coasts of North and South Carolina, Georgia, and Florida with Tropical Storm Chris lurking off the shores of the Carolinas. The officers and crew of NOAA Ship Pisces have been busy all morning preparing for departure and do not seem too concerned about the weather. There are a lot of moving parts on a ship this large with deck hands busy at work repairing, maintaining, and preparing equipment for this leg of the survey. A concern of the scientists is that a large refrigerator that is used to store bait fish is not operable, and after trying to repair the current one, as well as trying to find a replacement, it was decided that the survey leg should not be delayed so we will make due. One set of traps were set about 5 miles off the coast the first day with a haul of black sea bass, tomtate, gulf flounder, pigfish, pinfish, and a type of porgy. Each of the chevron (V-shaped) traps (Figure 1) have bait fish inside that attract the species and are fitted with two GoPro cameras, one facing the front and one facing the back of the trap. A numbered buoy is attached and then the trap is sent overboard and allowed to sit on the seafloor for about 90 minutes. Once the deck crew retrieve the traps, the fish in each trap are first sorted and then weighed and measured and then released back into the sea. A pre-determined number of fish are kept for additional analysis that includes the removal of gonads and otoliths–more on this in a future post.

IMG_6425

Figure 1. Chevron traps ready to deploy. (photo by David Knight)

One may ask, “If you are trying to conserve fish species, why are you killing them?”  A number of the fish that are caught are returned back to the sea successfully because of the speed and efficiency of the scientists that are removing the fish from the traps and taking the various measurements; however, some fish are killed in the process.  By taking small samples of fish at a variety of locations within the study area, a bigger picture of the overall distribution and abundance can be determined which will then allow for the proper management of important fish species in the Atlantic. The numbers of fish trapped are insignificant in the bigger picture.  As an example, approximately 200 metric tons of Black Sea Bass were caught off the coast of North Carolina in 2015 and 2016; today we caught a few hundred fish in the traps. What the scientists take is like putting a drop of food coloring in an Olympic-sized swimming pool–it is insignificant in the overall scheme of managing populations.

 Personal Log

The great American writer Mark Twain said, “Twenty years from now, you will be more disappointed by the things you didn’t do than those you did. So throw off the bowlines. Sail away from safe harbor. Catch the wind in your sails. Explore. Dream. Discover.”

Being in a classroom is much different than being in the field (or in this case, on the ocean) doing research.  I am determined to try my hand at as many tasks as I am allowed, and to experience as much as possible without getting in the way of the crew and scientists. When will I ever have another chance to remove gonads and otoliths from fish or string bait lines at 7 a.m.?  When a remora was captured, Dr. Bacheler recommended I experience the great sucking power of this fish, and paraphrasing Mark Twain, “I threw off the bowlines and explored.” I now have a nice remora hickey on my forearm even eight hours later and have decided to question the notion that remora and the animals to which they attach have a mutualistic relationship.  “Why would you do this?” you may ask, because the opportunity was there of course!

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Figure 2. Remora doing what a remora does! (photo by Nate Bacheler)

Did You Know?

 Many marine fish are capable of changing sex during their lifetime in a process called sequential hermaphroditism. Black Sea Bass (Centropristis striata) begin their lives as a female and may change to a male during their life depending on population conditions. This type of hermaphroditism is called protogynous (“proto-“ first or original; and “gyno-“ woman) hermaphroditism. In California, a common species of fish that undergoes protogynous hermaphroditism is the California Sheephead (Semicossyphus pulcher).

References:

NOAA Office of Fisheries. National Marine Fisheries Service. Commercial Fisheries Statistics. [https://www.st.nmfs.noaa.gov/commercial-fisheries/]

 

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