NOAA Teacher at Sea
Aboard NOAA Ship Delaware II
July 25 — August 5, 2011
Mission: Clam and Quahog Survey
Geographical Area: North Atlantic
Date: July 27, 2011
Weather Data from the Bridge
Location: 40 08.301N; 72 07.278 W
Wind: NW @ 10
Conditions: Breezy, choppy water but warm and sunny, very few clouds
Science and Technology Log
We had an interesting night last night – quite a show from the lightning all around us. We had to stop working on deck due to lightning concerns and the water was definitely choppy. Shortly after midnight we resumed our survey dredging
A little history and information about the ocean quahog is in order, since we’ve been spending most of our time the last few days collecting, counting, weighing, and measuring them (along with a few other things we dredge up – more about those later).
The ocean quahog, or Artica islandica, is a marine bivalve member of the phylum Mollusca. It is native to the North Atlantic (where we are right now) and is commercially harvested as a food source. The ocean quahog lives in deeper water than the more common clam (the ones you can dig up along the beach) and are collected in much the same way as we are doing on the Delaware II, by dredging the bottom, rinsing off the mud, and throwing away all the other things brought up.
One of the unique characteristics of the ocean quahog is its longevity. They are known to live over 100 years. They are extremely slow-growing and as adults, may take years to add any measurable length to their shells. Both water temperature and population density appear to play a role in their growth. From previous NOAA studies, some of the fastest growing populations occur at the Georges Bank region off the coast of Massachusetts. The National Marine Fisheries Service (NMFS) uses the data collected from this survey to advise policy makers on the best way to protect and ensure the survival of the ocean quahog populations.
So what do we know so far about the ocean quahog’s populations? Besides the fact that they grow slowly, we know they are suspension feeders of phytoplankton and they themselves are food for a variety of other invertebrates including crab, sea stars, urchins, and some fish such as cod. The dredging process damages some ocean quahogs making them susceptible to other predators such as sculpin, skates, and flounder. Every three years the populations in the Northern Atlantic are surveyed and past results indicate the populations are stable despite the dredging methods of collection. The ocean quahog is not considered endangered at this time and is not considered overfished.
The lightning storm was beautiful to watch – the only thing missing was the thunder! Our ship never stops so the engines run continuously, making hearing anything on deck almost impossible. We’ve brought up some incredibly interesting animals – some I’ve never seen or heard of. For example, we’ve brought up numerous “sea mouse” samples.
They are actually carnivorous worms who live on the ocean floor and are covered with long hair-like threads, or setae. The ones we’ve brought up are 4-6 inches long. Creepy!
We are currently at survey site 229 which for you students translates to trial number 229. No more complaining to me about having to repeat your experiment 25 times!