Magellan

"The sea is dangerous and its storms terrible, but these obstacles have never been sufficient reason to remain ashore." 

- Ferdinand Magellan

In grad school, one of my friends used to say that he was a professional reader. At the time, he was working on a review paper that would constitute the introduction to his thesis, so he wasn't entirely wrong. I think he read a few hundred papers that year. He had to be deeply familiar with his field in order to craft the review. 

Atlantic sea scallop, Placopecten magellanicus.
Can you see the growth rings?

Science involves not just the search for knowledge but a familiarity with all previous knowledge. Right now, I find myself in a phase that could very well be described as "professional reading." I've read some 50 papers about sea scallops in the last week. My eyes are getting tired. 

Why am I busy ingesting scallop facts, you ask? There's a good reason, trust me. One of my colleagues at WHOI recently invited me to collaborate on a proposal about sea scallops. He even asked if I would be comfortable leading the proposal, so you better bet I'm going to learn everything I can about scallops before we submit. I need to know what I'm talking about. 

Sea scallops, Placopecten magellanicus, are the basis for one of the most lucrative fisheries in the U.S. Every time you order a perfectly-seared scallop at a restaurant, that succulent morsel started in the ocean. Properly managing a sustainable scallop fishery requires scientific research - and lots of it. Scallops are broadcast spawners with larvae that spend over a month in the water column. From year to year, there are huge variations in spawning, survival of larvae, and the ocean currents that carry them to their new homes. All those factors contribute to scallop recruitment - how many scallops reach the seafloor and survive to enter the fishery. Predicting scallop recruitment is a nasty, hairy mathematical challenge, but it's also key to maintaining a stable stock of scallops. If managers close off an area that has no scallop recruitment but open an area to fishing that has a ton of baby scallops trying to grow, we might disturb the population and not have any scallops to fish the following year. It's a complex problem, and that's why fishery managers partner with scientists to figure it all out. 

The white dashed line shows the outline of the larval shell on
a scallop. There's also a hitchhiker! The white arrow points to
a small limpet that's living on the scallop shell. 

One really cool thing about scallops is that they keep records in their shells. Over the course of their lifetime, each scallop is constantly working to grow new shell. The shell they made when they were young sits close to the hinge, and the newest part of the shell is out at the edge. They grow faster in the summer, when food is more available, and slower in the winter, when there's not quite so much to eat. This pattern results in annual growth rings in the shell, much like a tree. If you count the rings, you can tell how old the scallop is. 

If you have a small scallop that's recently settled on the seafloor, you might even be able to tell where it came from and what environmental conditions it experienced along the way. Scallops keep their larval shell after metamorphosing and settling on the seafloor. In a lot of species, the larval shell gets eroded away, so you really can't see it after a while. I wanted to test whether young juvenile scallops still have visible larval shells and whether I could use them for measurements in our study. 

My team's partners at the Cape Cod Commercial Fishermen's Alliance sent out a request to the fishermen: grab a few small scallops next time you're out fishing, so Kirstin can do a test. A few days later, one of the CCCFA staff members showed up at my house in the early morning with a bag of 10 frozen scallops, and I brought them to the lab. 

Thankfully, I can actually see the larval shell under the microscope! It's a bit difficult to discern the edges, especially in the larger scallops, but the shell is not eroded away. I should be able to use the calcareous records of environmental conditions to tell what each scallop experienced when they were tiny, vulnerable larvae. 

My team still has a lot of work to do in developing our proposal, but I'm excited for the process. With any luck, we'll have a fun scallop project to do soon!