Friday, May 13, 2005

Good afternoon, everyone. Boy, today has been a busy day both on the ship and off. We’ve lost one team member and gained three others; Daniela left the ship to attend a conference in Vancouver, British Columbia, so Kate will be alone collecting acoustic and CTD data. Sarah Goldman from SC Department of Natural Resources has taken Daniela’s bunk. She will assist Athan in deploying and recovering the chevron traps. Kevin Grant also boarded the R/V Nancy Foster for the first time. He is a fellow with the National Sea Grant Program and works with the National Marine Sanctuary’s Headquarters in Silver Spring, MD.

The day started with dives to the sandy and densely colonized habitat. The latter was full of “stinker” sponges and other sponges, as well as colonial tunicates. Don’t miss the amazing picture that Chris took during one dive to the densely colonized hard bottom habitat. Another diver, Dave, mentioned seeing a seahorse during one of his dives. Also, an observation of an illusive and unidentifiable pipefish is a rumor around the dry lab.

Today was quite different from the others; it is the first day for chevron trap deployment. To prepare for this survey, Athan is in charge of selecting sites, baiting the traps, preparing the measurement and degassing stations, and debriefing other team members (i.e., Sarah, Kate, and me) to assist with each step. Obviously, Athan cannot do all of the work for this survey alone so he debriefs us about the logistics in order to run efficiently and smoothly.

To prepare the traps, Sarah and Athan hang four bait stringers in each trap. Four menhaden dangle from the stringers in order to 1) simulate a school of fish, and 2) produce an odor to attract a variety of fish species. In addition, a couple extra menhaden are thrown into the bottom of the trap for luck. (It is Friday the 13th so we need all the good luck we can get.) Three traps are deployed 30 minutes apart from one another and will soak in the water for 90 minutes each.

The recovery of the traps creates an exciting time on the ship because, unlike the diving surveys, everyone has a chance to observe the life teeming underneath us. Once the trap is on deck, Athan, Kate, and I categorize the fish by species . This was a pretty easy process today because we only collected two distinctly different species of fish: black seabass and scup (also known as long spine porgy). However, we were shocked to find the first two traps contained 10 black seabass (picture to left) which had been tagged on a previous expedition in October 2004 to assess abundance and growth parameters.

Once the fish were separated, Athan and Sarah worked hard to remove excess air trapped in the swim bladder of the fish. The air pressure at the water’s surface is much lower than that of the deep ocean, so the air in the fish’s swim bladder expands as it is brought up to the surface without having time to escape, as it would under natural vertical migrations in the water column . Unless our team releases the air by using a sharp needle to poke through the fish's scales and into the swim bladder, the fish will not be able to swim down into the water column once they are released. As a result, the fish will float to the water's surface and most likely become a meal for some other hungry fish.

After the air is removed, the fish are weighed, measured, and released. Today, I was in charge of weighing and measuring the scup and black seabass (picture to right). My bunkmate, Kate, can attest that it is a messy and smelly process … but it sure is a lot of fun! Sarah Fangman mentioned that she loves the smell of fish…you know you are among kindred spirits after hearing a statement like that! After weighing and measuring the fish, I relayed the data to Sarah or Kate. They were responsible for writing down the data on the sheets and keeping the data organized for Athan when he returns to the lab in Charleston.

As you can see, each survey takes a concerted effort among many people aboard the ship. I am very proud to be a member of this hard working, yet fun-loving team of marine scientists. I just wish you were here to experience it with me.

If any of these experiences interests you or raise any questions, I’d love to hear them. Please email me at

See you then,

P.S. I cannot wait to do it all over again tomorrow!

Gray’s Reef National Marine Sanctuary:
Daily Connections to Scientific Inquiry & Nature of Science

Inferences in Science:

The science team cannot count, weigh, measure, and identify every fish in the sanctuary, so we must sub-sample the area in order to make conclusions about the total fish population. This is one aspect that makes science different from other ways of learning about our world. In this process, scientists use random sampling measures to ensure that their samples are not biased. We want the samples to be as accurately characteristic of the sanctuary as possible and free of prejudice, favoritism, etc. For example, if we only surveyed the densely colonized hard bottom habitats to make our inferences about the entire sanctuary, our conclusion would be far from accurate. This is because this habitat traditionally yields a greater diversity and abundance than other habitats in GRNMS. There are many different habitats within the sanctuary, each being characterized by variations in fish abundances and diversity.


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