NOAA Teacher at Sea
Terry Maxwell
Aboard R/V Hugh R. Sharp
June 6–21, 2017
Mission: Sea Scallop Survey
Geographic Area of Cruise: Northeast Atlantic Ocean
Date: June 14, 2017
Weather Data from the Bridge
Latitude: 41 31.54 N
Longitude: 70 40.49 W
Wind Speed 10 Knots (11.5 mph)
Air Temp 20.2 C (68.4 Fahrenheit)
Science and Technology Log
Contrary to the popular Rolling Stones song “Time is on my Side,” time is not on our side while we are taking survey of the scallop population in the Northeast Atlantic Ocean. This survey has been meticulously planned for months leading up to the actually event. There is no time budgeted to sit at a dredge station longer than you have to.
For seven days our noon to midnight science crew has been working at a blistering pace to dredge the ocean floor or take pictures with the underwater camera, HabCam. We are on a tight schedule, and in a twelve hour period we are able to work through 10 dredge stations. There has been little down time, and because some of the dredge stations are so close together, there is no time to be unproductive while we are at a station. Because of this, there are often stations where we simply are not able to individually count all the organisms we collect. There are many situations where our crew must use the method of subsampling.
For you in the Midwest, imagine you wanted to know how many dandelions were in your yard. Now if you are anything like me, you have way too many to count. If you went to count them all individually, it would literally take you all day if not more. It is just not time efficient to do such a thing. But if we took a population sample of some random areas in the yard, we could come up with an answer of how many dandelions were in the yard, and get a very close answer to actually counting them individually.
A similar example I can give you is with a recent dredge catch that was full of sand dollars. In one of our massive dredge catches composed of about 99.5% sand dollars, I completed an estimate sand dollars in a similar manner. I filled 2 liter pail full of sand dollars. My count for that pail was 188 sand dollars per 2 liters. In this catch we had 46 baskets each with a volume of 46 liters. So at 94 sand dollars per liter with there being 2,116 liters total, you can estimate there are about 198,904 sand dollars in that dredge catch.
We are faced with similar tasks while sorting through the dredge. When we face those situations, we turn to the method of sampling, and we take a representative sample of our catch. At most stations we are taking count of sea stars, crabs, waved whelks, all fish, and scallops. When we collect the dredge, most of the time it would not be time efficient to totally count up all the sea stars, so we turn to subsampling.
Here’s how subsampling works. Once we have sorted our dredge catch into various pails, we count up our specimens. For sea stars however we always take a subsample. To do that our watch-chief takes a scoop full of whatever is in our discard pails, and she does this randomly. She puts the random sample in a 4.5 liter pail. From here, she can begin to estimate the number of sea stars in our dredge catch. For example, if she goes through the 4.5 liter pail and finds six sea stars, and she knows there are four 46 liter pails of discard from the dredge, with a little math work she can figure out how many stars are in the dredge. If there are four 46 liter pails of discard, then there is a total of 186 liters of discard. She knows from her random sample that there are 6 sea stars per 4.5 liters which would come out to 1.3 sea stars per liter. By multiplying that number by 186, you can determine that an expanded estimate for the sea stars in the dredge collection would be 242 sea stars.
We also use this method when we have a large catch of scallops. When we have an overly large scallop catch on the dredge, we are not able to count and measure every single scallop from the catch. In these cases we use a representative amount. In one case we caught 24 baskets of scallops, each basket able to hold 46 liters. If we were to measure all of those scallops we would be at that station far too long to move onto the next dredge. When we caught enough scallops to fill 24 baskets, we used 3 baskets of scallops as a representative amount. All of the scallops in the 3 baskets were measured for their shell height. We would then take a mean average from these scallops to represent the 21 other baskets. We are also able to estimate the number of scallops in the 24 baskets the same way I estimated the number of sand dollars in a dredge catch.
Representative samples and population estimations through sampling are valuable tools that scientists use to collect a lot of data in a more efficient amount of time. From this data, mathematical models and predictions are developed. By implementing these methods, we are able to get more data from more locations.
Personal Log
It has been 9 days since I arrived in Woods Hole, Massachusetts to be a part of this journey. As I shared in my last blog, it is hard to be away from home, but many of the people here are gone more than 100 days per year. There is one thing that makes that time away easier….eating! Here on the Hugh R. Sharp, I would imagine I’ve put on some extra pounds. Most days I feel like a cow grazing. There are so many snacks on board, that it is so easy just to walk by the galley and grab a mini candy bar, chips, pop, or ice cream. I have discovered there is no better candy bar than a Baby Ruth. On top of the snacks and sweets, the cook, Paul, cooks up some mean dinners. Though I miss my wife’s home cooking, Paul’s cooking is a good substitute.
Outside of eating, there is not much recreational time on the ship. I do try to get up a couple hours before our shift begins to just enjoy being out on the ocean. I haven’t been able to make myself get up yet for sunrise at 5:05 AM. After working a twelve hour shift sorting dredge catches, there’s not much you want to do but sleep. Sleeping on the boat has been good. Probably some of the deepest sleep I’ve had since our kids were born. I’ve gotten used to the motion of the boat, the sound of waves hitting the bow, and the boat stabilizers which sound like a giant snoring. I’m a sleep walker, so that was a concern coming in that I would find myself on deck, sleep walking. But I’m sleeping so sound, I don’t think it’s possible. However I did warn my roommates to stop me if they saw me up in the middle of the night.
Part B of the survey has started, and with that most of my crew got off the ship, and I will have a new crew starting today. It was a great group of people to work with.
Did You Know?
Living in Illinois, there are not many times where knowing your parts of a ship come in handy. However, as I have been living on the Hugh R. Sharp for over a week now I have picked up some terms. I did not know many of these coming on, so this is a “Did you know?” moment for me.
Front of the ship: bow
Back of the ship: stern
Moving to the front of the ship: forward
Moving to the back of the ship: aft
If you were on the bow, your left would be the: port
If you were on the bow, your right would be the: starboard
Fathom: 6 feet
A heading of zero: North, a heading of 90: East, a heading of 180: South, a heading of 270: West
Heading to a location quickly: steam
Kitchen (where I constantly graze in between dredge stations): galley
Location of the ship’s navigational equipment is: bridge
Bathrooms: the head
Not much use for these terms in the Midwest!